Water Resources and Water Management

WATER RESOURCESAND WATER MANACEMENT DEVELOPMENTS I N WATER SCIENCE, 28 OTHER TITLES I N THW SERIES 1 G. BUGLIARELLO ...

Author: Milan K. Jermar

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WATER RESOURCESAND WATER MANACEMENT

DEVELOPMENTS I N WATER SCIENCE, 28 OTHER TITLES I N THW SERIES

1 G. BUGLIARELLO AND F. GUNTER COMPUTER SYSTEMS A N D WATER RESOURCES H.L. GOLTERMAN PHYSIOLOGICAL LIMNOLOGY

2

Y.Y. HAIMES, W.A. H A L L AND H.T. FREEDMAN MULTIOBJECTIVE OPTIMIZATION I N WATER RESOURCES SYSTEMS: THE SURROGATE WORTH TRADE-OFFMETHOD

3

J.J. FRIED GROUNDWATER POLLUTION

4

N. RAJARATNAM TURBULENT JETS

5

6 D. STEPHENSON PIPELINE DESIGN FOR WATER ENGINEERS

v. HALEK AND J. SVEC 7 GROUNDWATER HYDRAULICS 8 J.BALEK HYDROLOGY A N D WATER RESOURCES I N TROPICAL AFRICA 9 T.A.McMAHONANDR.G.MElN RESERVOIR CAPACITY A N D YIELD

10 G.KOVAC5 SEEPAGE HYDRAULICS 11 W.H. GRAF AND C.H. MORTIMER (EDITORS) HYDRODYNAMICS OF LAKES: PROCEEDINGS OF A SYMPOSIUN 12-13 OCTOBER 1978, LAUSANNE, SWITZERLAND

12 W. BACK AND D.A. STEPHENSON (EDITORS) CONTEMPORARY HYDROGEOLOGY: THE GEORGE BURKE MAXEY MEMORIAL VOLUME 13 M.A. M A R I ~ ~AND O J.N. LUTHIN SEEPAGE A N D GROUNDWATER 14 D. STEPHENSON STORMWATER HYDROLOGY A N D DRAINAGE 15 D. STEPHENSON PIPELINE DESIGN FOR WATER ENGINEERS (completely revised edition of Vol. 6 i n the series) 16 w. BACK AND R . L ~ T O L L E(EDITORS) SYMPOSIUM ON GEOCHEMISTRY OF GROUNDWATER 17 A.H. ELSHAARAWI (EDITOR) I N COLLABORATION WITH S.R. ESTERBY TIME SERIESMETHODS I N HYDROSCIENCES 18 J.BALEK HYDROLOGY A N D WATER RESOURCES I N TROPICAL REGIONS 19 D. STEPHENSON PIPEFLOW ANALYSIS I.ZAVOIANU MORPHOMETRY OF DRAINAGE BASINS

20

21 M.M.A. SHAHIN HYDROLOGY OF THE NILE BASIN

22 H.C.RlGGS STREAMFLOW CHARACTERISTICS

23 M. NEGULESCU MUNICIPAL WASTEWATER TREATMENT L.G. EVERETT GROUNDWATER MONITORING HANDBOOK FOR COAL AND O I L SHALE DEVELOPMENT

24

25 W. KINZELBACH GROUNDWATER MODELLING: A N INTRODUCTION WITH SAMPLE PROGRAMS I N BASIC D. STEPHENSON AND M.E. MEADOWS KINEMATIC HYDROLOGY AND MODELLING

26

27 A.M. E L SHAARAWI AND R.E. KWIATKOWSKI (EDITORS) STATISTICAL ASPECTS OF WATER QUALITY MONITORING - PROCEEDINGS OF THE WORKSHOP HELD A T THE CANADIAN CENTRE FOR INLAND WATERS, OCTOBER 1985

WATER RESOURCES AND WATER MANAGEMENT MILAN K. JERMAR Becker Gundhalstr., 18,0-8000Munchen 71, F.R.G.

E LSEVl E R Amsterdam - Oxford - New York

- Tokyo

1987

ELSEVIER SCIENCE PUBLISHERS B.V. Sara Burgerhartstraat 25 P.O. Box 21 1, 1000 AE Amsterdam, The Netherlands

Distributors for the United States and Canada: ELSEVIER SCIENCE PUBLISHING COMPANY INC. 52, Vanderbilt Avenue New York, N.Y. 10017, U S A .

Lihrsrv I d C(r*i!gressCataloginl-in-Publicofion Data

J e r m a r , M i l a n K. W a t e r r ~ s o u r c e s a n d w a t e r management. ( D e v e l o p m e n t s in w a t e r s c i e n c e ; 28) B i b l i o g r a p h y : p. I n c l u d e s index. 1. Water-supply. 2. H y d r o l o g i c cycle. .. 1 1 . Series.

TD345.Jh7 1987 553.7 ISBN 0-444-42717-1 (U.S.)

1. Title.

86-24114

ISBN 0-444-42717-1 (Val. 28) ISBN 0-444-41669-2 (Series) 0 Elsevier Science Publishers B.V., 1987 All rights reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the publisher, Elsevier Science Publishers B.V./Science & Technology Division, P.O. Box 330, 1000 A H Amsterdam, The Netherlands. Special regulations for readers in the USA - This publication has been registered with the Copyright Clearance Center fnc. ICCC), Salem, Massachusetts. Information can be obtained from the CCC about conditons under which photocopies of parts of this publication may be made in the USA. All other copyright questions, including photocopying outside of the USA, should be referred to the publisher. Printed in The Netherlands

V

C O N T E m Page Chapter 1

WATER OCCURRENCE AND ITS FUNCTION I N NATIJRAL SYSTENS

1.1

SYSTEMS OF THE NATITRAT, ENVIRONMENT

1.2

ENERGY INPUT AS A CALJSE OF

1.3

HYDROLOGIC CYCTX SYSTEM

THE HYDROIBGIC CYCLE

1

3 8

1.3.1

Evaporation

10

1.3.2

Precipitation

18

1.3.3

Interception

21

1.3.4

Depression and Detention Storage; Overland Flow

22

1.3.5

Infiltration

23

1.3.6

Subsurface Water Movement

25

1.3.7

Flow i n Channel Network

32

1.4

INTERREMITION OF SURFACE AND GROUNDWATER RUNOFF

1.5

GROUNDWATER LEVEL REGTJTATION, SOIL kDISTURE AND SOIL

33

STRUCTURE FORMATION

40

1.6

CLIMATOLOGICAL FUNCTIONS OF WATER

45

1.7

AICGEOCHENICATJ CYCLE SYSTEM

50

1.7.1

Cycle

55

Water Quality a s a Product of i t s C i r c u l a t i o n

60

HYDROLOGIC CYCLE AS REGULATOR OF B1OZI)GICAL PROCESSES

71

1.7.2

I .8

Water Erosion a s a Process Evoked by t h e Water

1.8.1

I n t e r r e l a t i o n s h i p s of Aquatic Ecosystems and Water Q u a l i t y

1.9

RUNOFF PROCESS AS REGITLATOR OF THE LIVING ENVIRONMENT

77

83

VI

Chapter 2

WATE3 AND ITS FLWCTION I N SOCIA;, SYSTENS

2.1

CATEGORIES OF WATER mILIZATION

86

2.2

WATER REQUIREYEFTS AND WATER CONSUMPTION

88

2.3

IN-STRmY AND ON-SITE WATER USE

93

2.3.1

Waste Disposal

94

2.3.2

Inland \.!a t e r Transport

103

2.3.3

Water Power U t i l i z a t i o n

111

2.3.4

Water f o r Recreation

115

2.4

X D I C I P A L AND RURAL WATER REQUIREMENTS

2.4.1

2.5

Nater Requirements f o r Drinking and Cooking Purposes

121

2.4.2

Water Requirements f o r Other Domestic Uses

130

2.4.3

Urban Public Water Requirements

134

2.4.4

Management of Water Delivery and Disposal

139

INDTJSTRIAL WATER SUPPLY

2.5.1

AND RE-USE SYSTEMS

144

Water f o r Processing, Nining and Hydraulic Transport

153

2.5.2

Cooling Water

155

2.5.3

Boiling and Steam Power Water

157

2.5.4

Water Losses i n Industry and F l m Chart of

2.5.5 2.6

120

Water Use

160

Waste [.la ters and Was t e - f r e e Technologies

165

WATER I N A G R I C I L T U W L SYSTEE

169

2.6.1

A g r i c u l t u r a l Production and A g r i c u l t u r a l Yield

I72

2.6.2

E f f i c i e n c y of I r r i g a t i o n Water IJse

181

2.6.3

Water for I r r i g a t i o n and i t s Q u a l i t y

185

VII

Chapter 3

2.6.4

I r r i g a t i o n a s Supplementary Watering

187

2.6.5

F e r t i l i z i n g and Remedial I r r i g a t i o n

191

2.6.6

Protective Irrigation

194

2.6.7

Soil kaching IrriEation

195

2.6.8

Irrigation bsses

197

2.6.9

Water f o r Livestock and Processing

2 04

2.6.10

Water P o l l u t i o n from Agricultural Production

2 01

WATER BALANCE AND WATER SYSTm

3.1

CHARACTERISTICS OF SURFACE AND GROUNDWATER RESOURCES

211

3.2

SAFE YIELD

213

3.3

BALANCE OF WATER RESOURCES AND NEEDS

220

3.4

MINIMUM WATER TABLE . &TI MINIMUM DISCHARGES

225

3.5

ACTIVE AND PASSIVE WATER BAIANCE

229

3.6

PROBABILITY OF THE SATISFACTION OF bJATER REQUIREMEIVE

233

3.7

FLOW CONTROL AND OPERATING SCHEDIJLES

239

3.8

SYSTENS I N WATER RESOIRCES MANAGEMENT

245

3.9

ANAJJYSIS AND MODELLTNG OF WATER RESOURCES SYSTENS

247

3.10 ECONOMIC OPTIMIZATION AND FINANCIAL APL4LYSIS

3.11 Chapter 4

PLANNING WDEL BASED ON PHYSICAL PARAMETERS

255 259

IMPACT OF DEVEJDPWNT ACTIVITIES ON THE HYDROIXIC CYCLE

4.1

CHANGES I N THE HYDROJDGICAL DATA

262

4.2

CHANGES I N THE HYDROLCGICAL BALANCE

265

4.3

INFLUENCE OF FORESTRY AND AGRICULTURE

271

4.3.1

I n t e r c e p t i o n , Evapotranspiration and I n f i l t r a t i o n

274

4.3.2

Influence of t h e Vegetative Canopy on Floods and Erosion

4.3.3

277

Influence of t h e Vegetative Canopy on R a i n f a l l and Runoff

2 82

VIII

4.4

INFJ,UENCE OF URBANIZATION AND INDlJSTRIAL,IZATION

2 87

4.5

CHANGES I N WATER QIJALITY

2 92

4.6

ENVIRONMENTAT, IMPACTS OF WATER DEVELOPMENT PROJECTS

299

4.6.1

Effects of Reservoirs and I r r i g a t i o n Systems on Climate

4.6.2

Effect of Reservoirs and Dam on Sediment Transport

309

4.6.3

Effect of Reservoirs on Water Quality

316

4.6.4

Effects of Man-made Lakes on the Biosphere

324

4.6.5

Effects of Flow Control and Water TJithdrawals

330

4.6.6

Effects of River Training and @en Channel Water Conveyance

Chapter 5

3 03

336

WATER DEVEIOPMENT AND MANAGEMENT POLICY

5.1

WATER MANAGEMENT ACTIVITIES AND ORGANIZATIONS

341

5.2

PARADOXES OF WATER RESOURCES DEVEIBPMEXI'

344

5.3

STRATEGY OF WATER RESOURCES DEVEIOPMENT

346

5.4

TACTICS OF WATER MANAGEMENT

351

5.5

NON-CONVENTIONAL TECHNIQUES OF WATER SUPPLY

361

5.5.1

Long-Distance Water Conveyance and Transportation

361

5.5.2

Conjunctive Use of Surface and Groundwater

5.6

Resources

3 63

5.5.3

Groundwater Mining and A r t i f i c i a l Recharge

366

5.5.4

Watershed Management

368

5.5.5

Weather Modification

370

5.5.6

Desalination and Treatment of bw-Quality Waters

372

CONCLIJSIONS

IX

IITRODIJCTION

Water is a substance which plays a c r u c i a l p a r t i n the existence o f l i f e on Earth. I t forms t h e l i v i n g mass and, together with the s o i l and t h e a i r , r e p r e s e n t s t h e l i v i n g environment. The energy which is accepted by t h i s system from the universe helps t o s u s t a i n e s s e n t i a l l i f e processes. The hydrological cycle, o r the process of permanent movement and transformation of water, connects the human being with a l l t h e elements of t h i s environment i n such a manner t h a t any change r e s u l t s i n a chain of consequences which spread throughout the ecologic a l system. For b i l l i o n s of years t h e development of t h e ecosystem was determined by the i n t e r p l a y of uncertain causes. A fundamental change occurred w i t h the emergence of c i v i l i z a t i o n . Man s t a r t e d t o influence t h i s system i n t e h t i o n a l l y and systematically: gradually mankind's everyday existence came t o have a more s e r i o u s and detrimental e f f e c t on t h e environment. Up u n t i l now t h e energy which mankind used during h i s development has been n e g l i g i b l e i n comparison with the amount of energy used through n a t u r a l processes. Nevertheless, even t h e water management and a g r i c i i l t u r a l a c t i v i t i e s of a n c i e n t c i v i l i z a t i o n s already had a d r a s t i c and i r r e p a r a b l e impact on waste a r e a s a s a r e s u l t of systematic e f f o r t s over long periods of time. Today t h e march of technology appears i r r e p r e s i b l e and i r r e v e r s i b l e throughout t h e world. The process of d e f o r e s t a t i o n , land c u l t i v a t i o n , urbanization and i n d u s t r i a l i z a t i o n a r e r a p i d l y changing t h e c h a r a c t e r of t h e e a r t h ' s s u r f a c e and the q u a l i t y of t h e water, s o i l and a i r , a s well a s a f f e c t i n g t h e acceptance of s o l a r energy. The s c a l e of these human a c t i v i t i e s has now reached such a proportion t h a t t h e impact of one s i n g l e generation is comparable with t h e impact of a l l preceding generations. The a m u n t o f energy c u r r e n t l y manipulated by man

is no longer n e g l i g i b l e i n comparison with t h e t o t a l a m u n t of energy used d u r ing n a t u r a l processes. C i v i l i z a t i o n confines t h e world and mankind t o mnotonous, unambiguous s t r u c t u r e s which a r e very d i f f i c u l t t o control e f f e c t i v e l y . Man a l t e r s t h e n a t u r a l equilibrium without considering t h e global consequences of h i s a c t i o n s . I n t h e course of a few decades he i s a b l e t o exhaust some natu-

X

r a l resources and i r r e v e r s i b l y p o l l u t e h i s environment. An unfavourahle accumul a t i o n of the negative consequences of h i s a c t i v i t i e s , t r a n s f e r r e d i n t h e framework of t h e hydrological c y c l e , threatens hi:; own existence. Man has s t a r ted t o l i v e a t t h e c o s t of f u t u r e generations. The r o o t s of t h i s incomprehensible s i t u a t i o n l i e not only i n mankind's m i s guided endeavour t o achieve maximum economic b e n e f i t s through minimum e f f o r t s and without considering secondary e f f e c t s , b u t a l s o i n h i s t r a d i t i o n a l thinking processes. These were formed i n t h e period when man s t i l l observed n a t u r a l phenomena s e p a r a t e l y , without taking account of t h e i r i n t e r r e l a t i o n s h i p . I n the p a s t t h e observer of n a t u r a l phenomena i n one s c i e n t i f i c d i s c i p l i n e had no reason t o follow up t h e i r i n t e r - d i s c i p l i n a r y r e l a t i o n s h i p s . The i n t e r r e l a t i o n s h i p of n a t u r a l phenomena and t h e l i k e l y consequences of such a r e l a t i o n s h i p

were not taken i n t o consideration.

This s i t u a t i o n is a l s o r e f l e c t e d i n t h e f i e l d of water resources. The theor e t i c a l background t o t h i s f i e l d i s t r a d i t i o n a l l y formed by: - h y d r a u l i c s ( t h e study of t h e physical r e f l i l a r i t i e s of water motion and function) ; hydrochemistry ( t h e study of t h e p h y s i c a l , chemical, b i o l o g i c a l and bacte-

-

r i o l o g i c a l p r o p e r t i e s of water) ; - hydrology ( t h e study of t h e time and space d i s t r i b u t i o n of various aspects of t h e hydrological cycle) and

-

I

hydrogeology ( t h e study of t h e occurrence and mvgnent of subterranean

waters and t h e i r geological environment). ?he d e s c r i p t i v e s c i e n t i f i c d i s c i p l i n e s a r e concerned with t h e study of two d i f f e r e n t c a t e g o r i e s of phenomena. The f i r s t category comprises phenomena which a r e based on simple r e l a t i o n ships among s e v e r a l v a r i a b l e s . Here i t is necessary t o neglect those v a r i a b l e s whose influence is unimportant and t o d e r i v e the mathematical r e l a t i o n s h i p s among these v a r i a b l e s whose influence is decisive.

The second category includes phenomena with a high degree of occurrence. Here it i s n o t necessary t o t r a c e t h e i r mutual r e l a t i o n s h i p s , b u t r a t h e r t o study t h e r e s u l t of t h e i r i n t e r p l a y , when t h e r e l a t i o n s between causes and consequences a r e t o be determined and c l a s s i f i e d on t h e b a s i s of s t a t i s t i c a l methods and t h e theory of p r o b a b i l i t y . However t h e s i z e and number of water p r o j e c t s and o t h e r development a c t i v i ties which influence t h e hydrological cycle have reached such proportions t h a t the majority of problems involved extend beyond t h e boundaries of the above t r a d i t i o n a l d i s c i p l i n e s . These problems cannot be solved with t h e t o o l s of the above methods. Present-day water management problems a r e i n t e r d i s c i p l i n a r y i n n a t u r e and a s such include complex phenomena with complicated mutual i n t e r r e l a t i o n s h i p s . These i n t e r r e l a t i o n s h i p s a r e more important than t h e number of

XI

v a r i a b l e s involved. It is not enough t o i n v e s t i g a t e these problems by researching s e l e c t e d im portant v a r i a b l e s and r e l a t i o n s h i p s . Using s t a t i s t i c a l methods and t h e theory of p r o b a b i l i t y f o r t h i s purpose represents a complicated mathematical e x e r c i s e with only l i t t l e relevance t o r e a l i t y . Such an approach is unlikely t o lead to the desired goal. The s o l u t i o n of i n t e r - d i s c i p l i n a r y problems i n water development and management p r a c t i c e on the b a s i s of the t r a d i t i o n a l approach tends t o ignore the key development and environmental f a c t o r s . This leads among o t h e r things to : - the s e p a r a t e development of e i t h e r s u r f a c e o r groundwater resources, - t h e use of high q u a l i t y water f o r low q u a l i t y requirements and v i c e versa, - t h e over-excessive use of water f o r c e r t a i n purposes, thus i n h i b i t i n g o r excluding m r e valuable u s e s , - t h e neglecting of water re-use, water re-cycling, and waste material recovery p o s s i b i l i t i e s and o t h e r water saving p r a c t i c e s , - t h e l o s s of n u t r i e n t s or raw m a t e r i a l s from t h e place of i m e d i a t e o r potent i a l l y easy u t i l i z a t i o n , and t h e neglecting of important secondary a s p e c t s , c o n s t r a i n t s and hazards of

-

many water and o t h e r development p r o j e c t s . The t r a d i t i o n a l approach i s a l s o one of t h e reasons o f :

-

over-excessive use of n a t u r a l resources, t h e i n c r e a s i n g d e t e r i o r a t i o n of t h e n a t u r a l environment, and the economic f a i l u r e of many water development p r o j e c t s . When i n v e s t i g a t i n g contemporary water development and management problems

including t h e i r e c o l o g i c a l , economic and s o c i a l a s p e c t s , i t is necessary t o analyze a l a r g e n m b e r of elements whose i n t e r r e l a t i o n s h i p s depend on the prev a i l i n g conditions. Such problems can be solved by l i m i t i n g t h e problem a r e a , simplifying i t t o t h e p o i n t of a n a l y t i c t r a c t a b i l i t y , and defining systems which preserve a l l v i t a l a s p e c t s a f f e c t e d by various p o s s i b l e amendments. A l l important elements and dynamic i n t e r r e l a t i o n s h i p s should be analyzed and not j u s t g e n e r a l l y , but a l s o on t h e b a s i s of t h e i r s p e c i f i c behaviour. I t is necessary t o employ a combination o f d i f f e r e n t p r o b a b i l i s t i c and a n a l y t i c methods, including modelling and i n v e s t i g a t i n g the s e n s i t i v i t y of t h e outputs t o t h e assumptions rrade and t o f a c e t s of t h e problem excluded from t h e f o m l a n a l y s i s .

Ney s c i e n t i f i c methods f o r t h e s o l u t i o n of t h e contemporary problems i n water management include analogy, o p e r a t i o n research, system a n a l y s i s and cybernetics. The d i s t i n c t i v e f e a t u r e s of these methods a r e t h e i r emphasis on measurement and on t h e use of conceptual models described i n q u a n t i t a t i v e t e r n , the v e r i f i c a t i o n of t h e i r t h e o r e t i c a l p r e d i c t i o n s , and t h e i r awareness t h a t concepts a r e conditional and s u b j e c t t o growth and continuous change.

This new approach should be defined within the framework of water resources management, i . e . within a complex of a c t i v i t i e s whose objective i s the optimum u t i l i z a t i o n of water resources with regard to t h e i r q u a l i t y and a v a i l a b i l i t y and the requirements of society. These water management a c t i v i t i e s should a t the same time a l s o ensure an optimum l i v i n g environment, above a l l through prot e c t i o n of water resources against deterioration and exhailstion a s well a s through the protection o f society against the harmful e f f e c t s of water. In the course of these a c t i v i t i e s water resources management should a v a i l i t s e l f of the e n t i r e spectrum of e x p l i c i t sciences, gradually coming t o form the sphere of i t s own theory. The present monograph deals with the fundamental i n t e r d i s c i p l i n a r y problems of t h i s complex sphere, an understanding of which i s indispensable for successf u l water resources mnagement i n the widest sense of i t s s o c i a l functions and environmental consequences.

1

Chapter 1

WATER OCCIJRRENCE AND ITS FUNCTION I N NATURAL SYSTJZMS

1.1 SYSTFNS OF THE NAATURAZ, ENVIRONMENT Water e x i s t s a s s c a t t e r e d humidity and a s s p a t i a l l y limited water formations below, on and above the Earth's surface. Water resources a r e water formations which can be u t i l i z e d by human society. Water and water formations a r e dynamic; they a r e always i n motion and t h e i r s t a t e of aggregation is forever changing. R e s e processes continue without i n t e r r u p t i o n , change i n space and time and trans form the n a t u r a l environment. The natural environment i s formed by a number of systems, o r complexes of mutually i n t e r r e l a t e d elements, whose relationships within the framework of these complexes a r e more important than t h e i r relations with the elements of other systems. I n the important p a r t of the n a t u r a l environment which constitutes the object of the present investigation i t i s possible to distinguish: (a) a b i o t i c systems, created by water, s o i l and a i r elements and characterized by: - morphological (topographical) d a t a

-

pedological and geological data ( s o i l is a mixed abiotic-biological element) hydrogeological and hydrometeorological data (b) biotic-biological systems (ecosys tems) , originating with the develop-

ment of l i v i n g matter i n a defined p a r t of the a b i o t i c environment and (c) socio-economic sys tems , i e. administrative, econcmic and technica 1

.

systems (Fig. 1.1) originating with the formation of human society and possessing important interconnections with the above two systems. The natural environment of Earth represents a semi-closed system. The input of matter i n t o t h i s system from outer space is negligible. The movement of matter inside t h i s system i s enabled by an input of energy, consisting mainly of s o l a r energy and the i n t e r n a l energy of Earth i t s e l f . This system, due t o i t s own homeostatic mechanisms and d e t e c t o r s , tends t o achieve a s t a t e of equilibrium balancing accidental deflections from t h i s s t a t e . The material couplings which form i n t e r r e l a t i o n s among these systems include: - biotic-abiotic couplings, e.g. the quantity of dissolved oxygen caused by the decay of a biomass abiotic-biotic couplings, e.g. the dependence of the i n t e n s i t y of biological

-

processes on water temperature

-

socio-abiotic couplings, e.g. as manifested especially by the h p a c t of

urbanization, i n d u s t r i a l i z a t i o n and a g r i c u l t u r a l production on runoff and sedimen t transport

2

-

socio-abiotic-biotic couplings, e.g. a s manifested by the r o l e of urbani-

zation, industrialization and intensive agricultural production i n polluting c e r t a i n ecosys tans

.

\

SYSTEMS

Fig. 1.1. The penetration of matter and energy through the a b i o t i c and b i o t i c ( a l s o socio-economic) systems. The equilibrium of relevant systems and its recovery depend on the energy and matter input: R detector, HM - hornyostatic mechanisms.

-

These material couplings a l s o form complex i n t e r r e l a t i o n s , such a s the

socio-abiotic-biotic-social i n t e r r e l a t i o n manifested by the influence of industrialization and the subsequent water pollution and eutrophication on

.

water u t i l i z a t i o n . The task of analyzing these interrelationships among the various systems is complicated not only by the complexity of the couplings and interrelations concerned, but a l s o by the lack of data available (Fig. 1.2). As only selected couplings a r e operationally controllable, only a few can be checked systematically. Moreover, because data monitoring i s neither cmplex nor f u l l y systematic, the relevant s e r i e s of data i n the different categories do not mutually correspond and a r e therefore inadequate. Furthermore, frequently undesirable secondary couplings occur and have a negative influence on the function of the system i n question, sometimes bringing about a gradual change i n the sys tern's behaviour .

Ihe movement of water and other matter within and between these systems changes i n t i m e and space: The importance of individual relations i s variable. Regarded i n this way the doctrine of water management concerns the s t r u c t u r e and the function of systems, thus enabling the water t o f u l f i l l its natural functions and t o be u t i l i z e d f o r the various present and future requirements

3

Fig. 1 . 2 . Basic productive inputs and outputs of a b i o t i c and b i o t i c systems. Monitored, i . e . s y s t e m t i c a l l y checked inputs a r e marked by a c i r c l e ; accidental, undesired outputs a r e marked by white arrows. 1.2

ENERGY INPUT AS A CAUSE OF THE HM)RO-iDGIC CYCLE

The Earth r e f l e c t s a p a r t of the external energy input which it receives, d i s t r i b u t i n g the r e s t between the a i r , water, s o i l and geological formations and radiating p a r t of i t back i n t o the Universe. "he basic equation of the energy balance expresses t h e law of the conservation of energy (Fig. 1.3)

- Jg

Ju

.

Ju

- sun and other

9 J

z?

-

( 1

-9

=

6

.Jk

(m*.kg.s-*)

radiation from the IJniverse (short wave)

albedo ( c o e f f i c i e n t of r e f l e c t i o n ) global radiation (long wave)

- energy J2 - energy J3 - energy J1

)

supply t o the atmosphere supply t o the hydrosphere supply to the pedosphere and lithosphere

(1.1)

4

J4

- enera

supply to the biosphere

Fig. 1.3. Basic inter.rrlat.ions of the systecls of atmosphere, lithosphere and pedosphere a s well a s the hydrosphere: movement of m t t e r i n the gravi ational f i e l d , enabled by the supply of energy, forming the main input. The input of m t t e r from the universe i s negligible.

F

The Earth r e f l e c t s on average 34% of the energy input. The coefficient of reflection, the albedo, depends essentially on the character and morphology of the surface, the s t a t e and quality of the atmosphere above, as well a s on the angle of incidence of the rays. Stretches of water r e f l e c t 10%of the energy on average, lawns 15%, forests 20%, deserts 30%and snow 80%. The type of

energy u t i l i z a t i o n changes with the character of the surface: 90% of the energy input is consumed by evaporation above oceans, while above continents the figure i s only 50%. The global average temperature of the a i r is not changing a t present. The energy balance does not demonstrate any increment i n the component: JI = 0 . I n average the basic equation of the energy balance, a l s o taking i n t o account the fact that the energy supply to the biosphere is relatively small, can be simplified a s follows: . Je = J2 + J3 Je

-

(m 2 .kp.s-2 )

effective radiation

The r e s u l t of the acceptance of the effective radiation are fluctuations i n the s o i l and water temperature, accompanied by evaporation with sublimition.

5 These processes change the state of water aggregation i n t o a gaseous one. The s p e c i f i c weight of water vapour is lower than t h a t of a i r . Water vapour r i s e s and i n t h i s way i t acquires p o s i t i o n energy. The thermal energy thus regenerates the mechanical energy of water and causes the c i r c u l a t i o n of water. The hydrol o g i c a l c y c l e i s an uninterrupted process of water motion and changes of aggregation i n t h e systems of t h e b i o l o g i c a l and a b i o t i c environment. The d i f f e r e n c e between the s p e c i f i c and l a t e n t h e a t of fusion and vaporization, whose values a r e a p p r o x i m t e l y two and t h r e e orders high r e s p e c t i v e l y , balances t h i s process during a higher o r lower energy input. The mechanical energy c o n s i s t s of the p o s i t i o n energy, the pressure energy and the k i n e t i c energy. Jh = m.g.h

The p o s i t i o n e n e r a

(m2.kg.s-2)

m

- mass

(kg)

g

-

(9.81 m.s-2)

h

- head

g r a v i t a t i o n a l constant

(m)

Pressure energy p

J = m . L

9

P

- pressure

Kinetic energy

-

v e l o c i t y of flow

(m2.kg.s-2)

.

(m-l. kg sH2)

- water d e n s i t y , u n i t mass of water

v

(1.3)

J

k

2 = m V

T

(kg .m-3)

(m2. kg .s - ~ )

(1.5)

(m.s-l)

,

The q u a n t i t y of water i n water courses forms only 0.002% of the t o t a l global water reserves. The proportion of water power p o t e n t i a l of water courses is only 0.4% of t h e 6.4

. lo3'

of energy which the Earth continuously receives

from t h e Universe. But i t is twenty times higher than the percentage of water courses volume i n r e l a t i o n t o t o t a l global water reserves because of t h e high head formed by geomorphological conditions. P o s i t i o n energy a c t s a s pressure energy and changes i n t o k i n e t i c energy, depending on t h e physical conditions. This k i n e t i c energy together with chemical energy of water and changes i n volume during ice formation, transforms s o i l and rock formations a l s o forming and changing r i v e r beds. The growth and changes i n ecosystems a r e a l s o enabled by the e f f e c t of t h e mechanical, thermal and chemical energy of water. By accepting and e m i t t i n g energy, water molecules change t h e i r p o s i t i o n and

state of aggregation during their course through the b i o l o g i c a l and a b i o t i c systems of t h e n a t u r a l environment. The law of conservation of energy during t h i s cycle expresses the equation of hydrological equilibrium:

6

P1

- vertical

P2

- horizontal

Q,

-

precipitation precipitation (see paragraph 1.3.2)

surface outflow (channel and overland flow)

Q2 - subsurface outflow (groundwater runoff) Q3 - deep percolation and juvenile water inflow El

-

evaporation frcm bare s o i l surface

E2

-

evaporation from free water surfaces

E3

- evaporation

E

-

4

from snow and i c e

evapotranspiration

R 1 - water increment (or decrement) in s o i l s and rock formations R2

- water

R3

- water

increment (or decrement) i n the atmosphere

R4

- water

increment of the flora

R5

- water

increment of the fauna.

increment (or decrement) i n water courses and reservoirs i n c l . depression and detention storage

The area and period of application of t h i s equation can be established i n such a way that relevant increments or decrements i n volume and the deep percolation or water supply from deep s t r a t a are negligible, thus simplifying the formula : P 1 + P 2 = Q 1 f Q2 + k=l & E k

(m3

(1.7)

This hydrological equation simply s t a t e s that the t o t a l evaporation and the difference between t h e t o t a l inflow and outflow (concentrated and overland runoff, groundwater runoff) i s formed by the precipitation and the dew deposit.

Data on the e a r t h ' s water reserves vary within a range of 210%.KORZUN and SOKOIDV (1976) estimated them a t 1,386 mld. krn3 , of which sane 2.53% or only 35 m i l . k m 3 , are fresh water reserves. The t o t a l annual evaporation is 577,000

km3 : 505,000 km3 on sea surfaces, 72,000 km3 on continental surfaces. Groundwater reserves 'exceed five thousand times the amount of water i n a l l rivers, brooks and creeks. 50% of the groundwater is below the level of 1000 meters under the e a r t h ' s surface (Tab. 1.1). Of basic importance in t h i s context is the recycling r a t e , which indicates the duration of the natural exchange of the relevant volume of water: i n the case of water courses this r a t e i s 3.4 .104 times as high as for groundwater.

7

TABLE I.. 1 ~

5 P e of format ion

Areg (10 2

kn 1

Ocean

361

Brackish groundwater Lakes

134.8 0.822

'Total

497

Groundwater Soil water

134.8 82

Volume (1g3

Layer (m)

Share total water

3700

96.5

km)

1 3 3 8 000 12 870 85.4 1 351 000

10 530 16.5

96 103.8 3660 78 0.2

0.94 0.006

97.45

(%) on

fresh reserves

~

Period of replenishment (years)

0

2500

0 0

1400 17

0

-

0.76 0.001

30.1 0.05

1400 1

Icebergs : Antarctic Greenland Arctic Mountain

13.98 1.80 0.23 0.22

Permafrost

21

21 600 2 340 83 41

1540 1298 369 181

1.56 0.17 0.006 0.003

61.7 6.7 0.24 0.12

9700 9700 9700 1600

300

14

0.022

0.86

10000

73.6 4.28 0.014 0.002 0.025

0.007 0.009 0.0002 0.0001 0.001

0.26 0.03 0.006 0.003 0.04

Fresh water: Lakes Marshes Watercourses Biosphere Amsphere Fresh water reserves Total water reserves

1.236 2.682 148.8

-

510

91.0 11.5 2.1 1.1 12.9

148

35 029

235

510

1 386 000

2719

2.55

100

100

2.55

17 5 16 d l h 8 d

-

World,water reserves and the share of different water bodies i n the resewe of the t o t a l volume of water and i n the volume of fresh water according to Sokolov (1981). The period of exchange of t h e i r volume by natural recharge (d - days, h - hour)

a O f the 145.103 km2 of c o n t i n e n t a l s u r f a c e s only two t h i r d s (100.10 3 km2 ) a r e

s u i t a b l e f o r water development, 25.10 3 km2 being permafrost, 14.103 krn2 icebergs and 6.103 km2 extremely a r i d land.

1.3 HYDROLEIC CYCLE SYSTEM The complicated processes of t h e hydrologic cycle include evaporation, prec i p i t a t i o n , i n t e r c e p t i o n and s u r f a c e s t o r a g e , i n f i l t r a t i o n and p e r c o l a t i o n , s u r f a c e and groundwater runoff. The catchment a r e a , i . e . the area which d r a i n s i n t o one place and thus cont r i b u t e s t o t h e runoff i n the p r o f i l e i n question, is an open system whose boundary crosses energy, water, a i r and s o i l / r o c k p a r t i c l e s . P o t e n t i a l energy of p o s i t i o n , thermal and chemical energy w i t h i n t h i s system, is transformed i n t o k i n e t i c energy and h e a t . Water, suspended, wash and bed load a s well a s f l o a t i n g d e b r i s a r e transported from the upper elevations towards the sea (and p a r t i a l l y v i c e versa e.g. by sand dune movement) and transfomed. Erosion, crushing, chemical and biochemical processes a r e a n i n t e g r a l p a r t of the water cycle (Fig. 1.4). The system of t h e catchment a r e a tends to achieve a steady state of operat i o n , corresponding t o t h e conditions of c l b a te, topography, geology and ecology, c h a r a c t e r i z e d a l s o by the f a c t t h a t the water and d e b r i s output corresponds t o a s p e c i f i c energy input. Any change e.g. by r i v e r t r a i n i n g , r e s e r v o i r construction, land c u l t i v a t i o n , urbanization and i n d u s t r i a l i z a t i o n ,

is a change of system elements and of t h e energy i n p u t , thus r e s u l t i n g i n the change of output . The state of t h i s system is t o be followed i n i t s s p a t i a l elements (Fig. 1.4). Three equations of balance can be formulated f o r each of these elements: - hydrologic balance (Fig. 4.1) - f a l l - o u t , e r o s i o n and d e b r i s balance - e n e r g e t i c balance. I n any s p a t i a l e l e m e n t due t o t h e equilibrium of t h e atmosphere branch, the p r e c i p i t a t i o n , the evaporation and t h e increment of atmosphere moisture eqcal t o the d i f f e r e n c e of water vapour e n t e r i n g and leaving the element: An

- An+I

An

- water vapour

An+l

= Rn + Pn

- water

-

En

(m3)

e n t e r i n g t h e s p a t i a l element n

vapour leaving the s p a t i a l element n

Pn

- precipitation

En

- evaporation

R,

-

and dew d e p o s i t i n t h e element n

i n the element n

a i r moisture increment i n t h e element n .

9

n

n-l

Fig. 1.4. Equation of hydrological equilibrium, the transport of mss and biogeochemical cycles a s subsystems of the water cycle. Explanation of symbols and main equations is given i n the t e x t . Precipitation i s formed by external water vapour supply A - An+l and by intern ~l evaporation E .

n'

Pn = An

- An+l

+ En

-

Rn

(1.9)

but Pn = Q, + En (see equation 1 . 7 ) and, therefore, An

- An+l

+ En

An

- An+l

=

Internal

4,

- Rn +

Rn

= Qn + En

(1.10)

evaporation over continents is generally lower than the external

water supply, requiring m r e energy and resulting i n the generally prevailing evaporation on the sea surface. This f a c t can be expressed by the water circu-

10 lation r a t i o , defined as

(1.11)

The value of- t h i s r a t i o over vaste areas is quite stable, e.g. for North America mm = 1.25, Asia and Europe mae = 1.51. 1 . 3 . 1 Evaporation Evaporation is a physical process by which water changes from the liquid s t a t e t o the vapour s t a t e through the transfer o i thermal energy. The change from s o l i d s t a t e without passing the usual intermediate liquid aggregation i s called sublimation. Evaporation i s the key process i n the water cycle: (a) i t i s the only one of the processes i n t h i s cycle during which the energy input exceeds the energy output, (b) i t accounts for the creation of living m t t e r . Evaporation takes place particularly on the boundary of the atmosphere and the hydro-, pedo-, and biosphere, thus making it possible t o distinguish: evaporation from open water surfaces, evaporation from bare s o i l surfaces, evaporation from snow and i c e , evaporation of water intercepted by vegetation, evapotranspiration from s o i l and vegetative cover, evapotranspiration of vegetative cover on water surfaces, evaporation from organic bodies and moist materials, evaporation i n the atmosphere. Evapotranspiration includes s o i l evaporation and the evaporation of water which i s absorbed by crops, used i n the building of plant tissue and transpired. The quantity of water evapotranspirated by plants and relevant s o i l surfaces per annum with the increment i n plant t i s s u e i s the consumptive use of plants. The hydroloEic balance can be expressed generally o r f o r a limited element of the lithosphere by the f o l l m i n g equation: ET = E + T = P, + R~ +

ET E T P Ri W

-

w -Q -F

(m3

(1.12)

evapotranspiration evaporation transpiration

- precipitation

- irrigation -

increase of water moisture caused by capillary forces from the groundwater

11 (+) or decrease by water consumption of crops (-)

Q F

- deep p e r c o l a t i o n - water chemically

and drained water and b i o l o g i c a l l y absorbed and used i n the building of the p l a n t t i s s u e (+), o r eliminated from the organic matter (-), e . g . by gut t a t i o n .

The r a t e of evaporation depends on the state of the systems whose i c t e r a c t i o n enables i t s course. The atmosphere influences t h i s course by m e t e o r o l e g i c a l f a c t o r s , namely by s o l a r r a d i a t i o n , humidity and by a i r movement leading away water vapours. The r e l a t i o n s h i p between r a d i a t i o n and evaporation can be expressed f o r a l i m i t e d p a r t of the hydro- o r t h e l i t h o s p h e r e ( r e s e r v o i r , f o r e s t , f i e l d e t c . ) by the equation (1.13) Je

-

effective solar radiation

Jh

-

h e a t accepted by t h e hydro- o r l i t h o - and biosphere

Ja

- heat

Jx

- l a t e n t h e a t used

t r a n s f e r r e d back t o the atmosphere f o r evaporation and evapotranspiration

The value and r a t i o of a l l these f a c t o r s a l s o change a t the same place i n the course of the y e a r (Fig. 1.5) Ja

i

AT

(1.14)

x=Dp Albrecht (1951) s i m p l i f i e s t h e equation f o r evaporation E =

Je - Jh 1 +%d

- temperature increment - a i r pressure increment 0: - c o e f f i c i e n t

AT AP

(1.15)

(% (Pa)

The t r a n s f e r of s o l a r energy is g r e a t l y influenced by overshadowing and by meteorological f a c t o r s , namely by the humidity of t h e a i r , p r e c i p i t a t i o n , a i r temperature and pressure a s w e l l a s t h e v e l o c i t y of i t s movement. Temperature and a i r p r e s s u r e do n o t influence evaporation d i r e c t l y . They c h a r a c t e r i z e the quantity of accepted energy. The humidity and a i r flow which a c c e l e r a t e the evaporation by t h e exchange of s a t u r a t e d a i r s t r a t a above t h e evaporating surface a r e a l s o i n c i d e n t a l phenomena of the energy t r a n s f e r to t h e atmosphere. They function a s r e w l a t i n g f a c t o r s of t h e evaporation and t r a n s p i r a t i o n r a t e .

12

-2 h 0

P n

Y0 E

4

-3

"Q

0

-1

'

5

4

6

7

8

9

10

month

Fig. 1.5. The annual course of the energy balance (Lake Haussee according t o measurements of Czepa and Schellmbergpr (1956). The energy input Jg i s part i a l l y r a d i a t e d (Jr), p a r t i a l l y t r a n s f e r r e d t o the atmosphere (J,) by the cont a c t of the water t a b l e and t h e a i r m s s . Je i s used f o r evaporation and Jt causes t h e change of water temperature. The imnediate cause of the evaporation process is the d i f f e r e n c e i n humidity between the i n t e r n a l and e x t e r n a l

-

or the s a t u r a t e d and unsaturated

-

system

of environment. I t can be characterized by the evaporation from s u r f a c e a s rel a t i v e humidity, i , e . t h e r a t i o of the a c t u a l water vapour pressure e (Pa) and t h e maximum

pressure E (Pa) which t h e a i r i s a b l e t o accept a t the a c t u a l

temperature. The d i f f e r e n c e between these values is the s a t u r a t i o n complement d = E - e

/Pa)

(1.16)

Rraslavskij and Vikulina (1954) assessed t h e following p r a c t i c a l formula f o r t h e computation of the evaporation from open water surfaces on the b a s i s of the a i r humidity and wind v e l o c i t y

Eva = 0.013

.

(eo

-

e2)

.

( 1 + 0.72 v2)

(1.17)

(m p e r day)

EV,

- monthly

eo

- rraximum water

e,

-

monthly average of water vapour p r e s s u r e 2 m above the water surface (m)

v2

-

average wind v e l o c i t y a t an e l e v a t i o n of 2 m above the water surface(m.s-l)

average of evaporation

vapour pressure, corresponding t o the average temperature of the water s u r f a c e (m)

Sermer (1960) e s t a b l i s h e d t h e r e l a t i o n between t h e temperature and the evaporat i o n from open water s u r f a c e f o r the conditions of Central Europe a s follows (0,0452 T Evd = 10

-

0.104)

T - average monthly temperature 2 m above the water s u r f a c e

(1.18) (OC)

Evaporation from snow and ice i s f i v e t o ten times lower than evaporation

from f r e e water s u r f a c e s . Due t o t h e lower temperature and s o l i d s t a t e of snow

13 and i c e , much m r e energy i s needed f o r the same intensity of its course. The evaporation r a t e from ice i s about 50 t o 100% higher than the evaporation from snow under the same conditions, because the heat conductivity of snow i s lower. Therefore

EM > E I > ES

(m)

(1.19)

- evaporation from open water surface EI ES

-

evaporation from ice evaporation from snow surface.

The value of evapotranspiratior; from overgrown water surfaces depend on the kind and the t o t a l quantity of the vegetable m t t e r . The evaporation from overgrown surfaces does not d i f f e r greatly from the evaporation from open water surfaces, when the water surface is only covered by f l o a t i n g leaves. But i t exceeds i t twice i n the case of the densely overgrown edges of reservoirs. Therefore

m => -

(m)

ELl

(1.20)

evapotranspiration from overgrown water surface.

Evaporation frcm bare s o i l does not depend on heat input only, characterized by meteorological factors, but a l s o on the s o i l f a c t o r s , namely on - the structure and other physical properties of the s o i l , the s o i l moisture , the contact of the s o i l layer with the groundwater surface (Fig. 1.6).

-

-

w

E

rnrn

(010)

i6

E

% 50

12

40

8 4

0

40

20

30 t c

DEPTH

Fig. 1..6. (a) I n t e r r e l a t i o n of the evaporation from the free water surface, the a i r humidity and the a i r temperature according t o Dub (1957). (b) Relation of the evaporation from the groundwater table on i t s depth, expressed a s the r a t i o of the evaporation from free water surface. Derived according to White (1970). These internal factors function clearly i n the case of lower s o i l saturation. The evaporation from bare s o i l s a l s o depends on the velocity of water inflow t o the surface. Inadequate water inflow lowers the evaporation r a t e .

14 Actual evaporation from bare s o i l s is, t h e r e f o r e , lower than the p o t e n t i a l r a t e , whose value depends on the energy supply only. Values of t h e p o t e n t i a l evaporation from b a r e s o i l s almost equal those from open water s u r f a c e s , when water evaporates d i r e c t l y from t h e wetted topographic s u r f a c e . Under conditions of a dry s u r f a c e l a y e r s , a s Penman (1940) proved, water vapour p e n e t r a t e s t h i s l a y e r by d i f f u s i o n , which lowers the values of evaporation. Evaporation from bare s o i l s takes p l a c e ( a ) i n c o n t a c t with t h e groundwater s u r f a c e , r e g u l a t i n g the s o i l moisture, o r , more f r e q u e n t l y , (b) without outstanding c o n t a c t with the groundwater s u r f a c e , when the suspended c a p i l l a r y water of t h e s o i l p r o f i l e i s n o t connected with the c a p i l l a r y water supported by the groundwater l e v e l , and the r o o t system does n o t penet r a t e i n t o t h i s space, i . e . when t h e groundwater l e v e l is influenced by the conditions of t h e s o i l s u r f a c e by means of hygroscopic and osmotic forces and by the gas pressure only. Evaporation from groundwater s u r f a c e s depends namely on the depth of the groundwater l e v e l . The course of groundwater l e v e l changes i s not the same under the conditions of evapotranspiration: Relevant forces d i f f e r , e s p e c i a l l y during the day. They a l s o depend on the kind of vegetation, i t s root system, I

s t a g e of growth and q u a n t i t y of leaves.

Evaporation w i t h i n reach of a w e l l can be c a l c u l a t e d by neglecting the evaporation during the n i g h t , which i s comparatively low, a n t i c i p a t i n g t h a t the

rise i n water l e v e l i s uniform: El

El

Q,

.

v

s

.v

- evaporation well

Q,

(24

- s)

(1.s-I)

(1.21)

from t h e groundwater surface w i t h i n the reach of the measured (1.s-l)

- w e l l y i e l d during the decrease of water l e v e l by 1 m (1.s-I) - v e l o c i t y of water level r i s i n g during n i g h t (m per hour) - t o t a l i n c r e a s e of water l e v e l p e r day (m per day)

I n t h e most frequent case of evaporation from b a r e s o i l s without outstanding c o n t a c t w i t h ' t h e groundwater l e v e l , the value of the evaporation r a t e i n t h e i n i t i a l s t a g e is almost equal t o the p o t e n t i a i evaporation. The following s t a g e , beginning with a s u b s t a n t i a l lowering of t h e moisture of the s o i l surf a c e , is characterized by the decreasing v e l o c i t y of evaporation, which s t a b i l i z e s i n t h e f i n a l s t a g e a t a low value. Anticipating a uniform d i s t r i b u t i o n of t h e perpendicular v e l o c i t y , Kutilek (1978) proves t h a t

e = (Wi

5 - Wo) . 'n .)

(m.s-'>

(1.22)

15 e

-

W.

-W -

evaporati-on rate

(m.s-l)

d i f f e r e n c e of moisture content i n t h e s o i l s u r f a c e during time t (%)

0 -D1 - average

d i f u s s i v i t y of t h e s o i l w a t e r , depending on the s o i l category and kf . dh

moisture kf - h y d r a u l i c c o n d u c t i v i t y h

-

t

- time

M

- c o n s t a n t of

pressure h e i g h t

s o i l properties.

T r a n s p i r a t i o n , t h e evaporation of water absorbed by a crop and not used i n the b u i l d i n g of p l a n t t i s s u e , may be above a l l s t o m t a l b u t a l s o appears a s c u t i c u l a r o r a s g u t t a t i o n o r exudates from c u t s u r f a c e s of t h e p l a n t . Transp i r a t i o n depends on p h y s i o l o g i c a l and environment (meteorological) f a c t o r s , e . g . daytime. P h y s i o l o g i c a l f a c t o r s i n c l a d e ( a ) t h e physiological s t r u c t u r e of r e l e v a n t p l a n t types, the age of t h e i r organ.; and t h e n a t u r e of t h e i r c e l l u l a r membranes, (b)

t h e a c t u a l s t a t e of the r e l e v a n t i n d i v i d u a l p l a n t , i . e . the degree of

n u t r i t i o n , namely w a t e r c o n t e n t of i t s c e l l s and water vapoyr content i n t h e t r a n s p i r a tory organs. Under c o n d i t i o n s of s u f f i c i e n t moisture and n u t r i t i o n f o r t h e development of i n d i v i d u a l p l a n t s , t h e i n t e n s i t y of t r a n s p i r a t i o n depends e s p e c i a l l y on envir o m e n t a l f a c t o r s , namely on s o l a r r a d i a t i o n , wind v e l o c i t y and s o i l moisture. The temperature of t h e l e a f exposed t o t h e sun is h i g h e r than t h a t of the a i r . In the case of a n i n s u f f i c i e n t supply of water and n u t r i t i o n , t h e i n t e n s i t y of t r a n s p i r a t i o n depends more on t h e above-mentioned i n t e r n a l p h y s i c a l f a c t o r s (Tab. 1 . 2 ) . The p l a n t e x e r c i s e s a l i m i t e d c o n t r o l on the t r a n s p i r a t i o n r a t e . Stomata IJSlJallY

open i n t h e l i g h t . They c l o s e w i t h reduced moisture and when the sugar

content d e c r e a s e s , changing t o s t a r c h , as happens i n t h e dark o r a t t h e end of the v e g e t a t i o n season, when leaves t u r n yellow. T r a n s p i r a t i o n is a l s o reduced i n the case of abundant water. The movement of water from t h e r o o t zone, through t h e stem and l e a v e s , is enabled by d i f f u s i o n and osmosis. The r a t e of both these processes is influenced by a i r moisture and energy supply, r e s u l t i n g i n t h e removal of water vapour next t o t h e l e a f s u r f a c e . Van Den Honert (1948) expressed t r a n s p i r a t i o n by physiological analogy w i t h OHM'S law

(1.23) T

-

transpiration r a t e

16 TABLE 1 . 2

Term,

Definition

IJsage

Theoretical value derived from energy input

Energy budget

S I P

Po ten t i a l

evaporation (evapora t i v i t y ) ET1

Ap

-

s a t u r a t e d vapour pressure increment

r - psychrometric Js

-

constant

energy input

Jg - energy t r a n s f e r Po t e n t i a 1

Evapotranspiration from s o i l and

Water balances f o r

evapotranspiration

vegetation sys tern, s a t u r a t e d with

long term planning

ET P

water and nutriments , derived from l o c a l hydrometeorological ccfiditions .

Optimal evapotrans-

Evapotranspiration from a surface

Determination of

p i r a t i o n ET OP t

whose s o i l moisture i s managed i n

p l a n t water and

order t o increase a g r i c u l t u r a l

i r r i g a t i o n require-

and f o r e s t r y production

ments

Highest evapotranspiration t h a t

Resistance a g a i n s t

r e l e v a n t vegetation system i s a b l e

moisture. Dimen-

t o achieve, dependent on i t s s t a g e of growth and a c t u a l state

sioning of the drainage.

Evapotranspiration of a p l o t i r r i g a t e d only f o r s u r v i v a l of

Resistance a g a i n s t drought

Maximum evapotransp i r a t i o n ET IlUX

Minimum evapotransp i r a t i o n ETmin

r e l e v a n t p l a n t species Actual evapotrans-

Real evapotranspiration dependent

p i r a t i o n ETa

OP

the growth s t a g e and state of

the p l a n t , measured by s o i l mois t u r e sampling, large-size lys imeters, zroundwater f l u c tua tioris Glossary of evapotranspiration.

Determination of actual irrigation rates

17 TABJX 1.3 ~

Cover

Bare s o i l

Grassland

Pine f o r e s t

X

Ratio

28.6

6.6

2.98

1.9 2.69

13.0

3.0

5.00

2.0

0.5 3.33

8.5

1.9 14.20

1.00

3.7

1 . 0 18.50

12.1

2.8 60.50

2.4

1.00

5.1

1.4 1.21

13.4

3.1 3.18

10.2

5.7

1.00

16.7

4.7

1.64

25.4

5.8 2.49

April

23.1

13.0

1.00

37.6

10.5

1.63

41.0

9.4

May

23.9

13.5

1.00

62.6

17.5 2.62

69.9

14.7 2.92

June

24.4

13.7

1.00

51.6

14.6 2.12

58.6

13.4 2.40

July

29.9

16.8

1.00

57.4 16.4 1.91

61.5

14.2

August

27.0

15.2

1.00

55.2

15.5 2.04

61.1

14.0 2.26

September

22.1

12.4

1.00

39.5

11.1 1.78

48.4

11.1 2.18

mrn

%

Share

m

October

9.6

5.4

1.00

18.2

5.1 1.75

November

2.6

1.5

1.00

7.0

December

0.6

0.3

1.00

January

0.2

0.1

February

4.2

March

Yearly t o t a l

177.8 100.0

1.00 ~

Share from

Loamy s o i l

Share

355.6 100.0 2.00 ~

50%

%

~~~~

Loamy s o i l

~

87%

f r e e surfac? evaporation

m

1.78

2.05

435.5 100.0 2.44 ~

~~

Depending on

70%

forest Sand

26%

Sandy s o i l

26%

density and age

Seasonal d i s t r i b u t i o n of evaporation and evapotranspiration, i t s dependence on the s o i l s u r f a c e and cover according t o Wechman (1963, Eberswalde, GDR). The share of evapotranspiration compared with the f r e e s u r f a c e evaporation according to Krecmer (1980).

18

-

evaporation rate

(m.s-’)

ys -

s o i l moisture p o t e n t i a l - s u c t i o n pressure of the s o i l water

(J.kg-’)

ye -

moisture p o t e n t i a l of the leaves

( J .kg-’)

et

rs

-

f l m r e s i s t a n c e of the s o i l

(Pa.s-1)

r

-

f l o w r e s i s t a n c e of the p l a n t

(Pa. s - l )

P

bLv - u n i t mss of the s o i l water

(k~.m-~)

The r a t i o of t r a n s p i r a t i o n and evaporation from s o i l changes a t one p o i n t i n time, namely during the vegetation season. A t the beginning of t h i s season, the evaporation from bare s o i l s dominates. Transpiration increases with the growing vegetation. Under the conditions of coherent p l a n t cover, t r a n s p i r a t i o n generally p r e v a i l s . Overshadowing of the s o i l surface by the v e g e t a t i v e canopy decreases the s o i l surface temperature and the r a t e of water vapour removal, thus causing a decrease i n t h e evaporation r a t e . Transpiration a l s o drops duri n g t h e period of ripening. Evapotranspiration is a complicated phenomenon, e x p l i c a b l e by a few values only ( s e e Tab. 1.2) complying with t h e following unevenness

ET1

>

ET P

>

ETm

>

ETo

>

ETa

>

ETmin

(1.24)

Under Central European conditions evapotranspiration by vegetation is generally higher than evaporation from bare s o i l s , but lower than evaporation from open water s u r f a c e s . Evapotranspiration from a r i d zone p l a n t s is o f t e n lower than evaporation from bare s o i l s . Gilimeroth (1951) and Kramer (1969) state t h a t evapotranspiration from vegetation never exceeds evaporation from s a t u r a t e d s o i l s a t the same l e v e l of exposure. 1.3.2

Precipitation

The p r e c i p i t a t i o n process i s the t r a n s f e r of water eliminated from the a t mosphere system t o t h e system of the hydro- and l i t h o s p h e r e , characterized by an output of the l a t e n t h e a t of vaporization. The number of d i f f e r e n t forms of p r e c i p i t a t i o n i s very l a r g e , but b a s i c a l l y p r e c i p i t a t i o n can be ( a ) v e r t i c a l , i . e . p r e c i p i t a t i o n from the upper p a r t of the atmosphere system, characterized by a v e r t i c a l movement of drops: d r i z z l e , r a i n , snow, g l a z e , h a i l , sleet e t c . , (b) h o r i z o n t a l , i . e . water eliminated by condensation o r sublimation on the ground: dew, hoar f r o s t , rime, diamond d u s t e t c . Depending on i t s s t a g e of agglomeration, p r e c i p i t a t i o n is e i t h e r l i q u i d o r s o l i d . I t is measured i n terms of depth (mn), r a i n f a l l i n t e n s i t y i n t e r n of

19

mn per minute. Rainfall is produced by a cooling of the a i r as the r e s u l t of a decrease i n the b a r m e t r i c pressure, by r a d i a t i o n , by c o n t a c t with a colder land o r sea surface o r during mixing of a i r masses. Condensation of water vapour i n t o cloud droplets takes place on condensation n u c l e i , formed by hygroscopic s a l t p a r t i c l e s . The f a l l i n g speed of d r o p l e t s is a function of t h e i r s i z e and of the speed of the a i r stream. The coalescence of t h e d r o p l e t s t o Eom raindrops is accounted f o r by the coexistence of t h e i c e c r y s t a l s and water d r o p l e t s and by the differences i n speed between l a r g e and small drops. The l a t e n t h e a t of evaporation r e g u l a t e s the process of condensation (Fig. 1 . 7 ) .

Fig. 1 . 7 . The subsystem of p r e c i p i t a t i o n and i t s processes i n dependence on the a1 t i t u d e according t o Mason (1957).

20 To sununarize the tendemy of r a i n t o occur i n d e f i n i t e p a t t e r n s , i t i s

p o s s i b l e t o d i s t i n g u i s h between: ( a ) l o c a l convective r a i n f a l l masses,

- caused

by the upward movement of a i r

(b) orographic r a i n f a l l - influenced by the morphology of the exposed p a r t of the higher mountain ranges and characterized by longer duration and lower intensity , ( c ) cyclonic r a i n - caused by the air-mass c o n t r a s t of cold and warm r a i n , i . e . by the excess of surface h e a t i n g i n lower l a t i t u d e s and of cold i n higher l a t i t u d e s , characterized by moderate l a s t i n g r a i n f a l l over a l a r g e a r e a , but a l s o by heavy r a i n , h a i l o r snowfall over a small a r e a . R a i n f a l l o f t e n occurs a s a combination of the above mentioned forms. Its occurrence, i n t e n s i t y and frequency depends on zonal, regional and l o c a l factors. The c o n t r a s t between surface h e a t i n g i n the equatorial and p o l a r zones, o r the d i f f e r e n c e i n temperature between t h e continent and t h e s e a , causes subs t a n t i a l movement of the a i r , which manifests t h e homeostasis of t h i s system, i . e . i t s tendency t o achieve a balanced, s t a b l e state. This mowment of a i r i s influenced by the r o t a t i o n of t h e Earth and by regional thermal and orographic f a c t o r s . Regions with a high h o r i z o n t a l inflow of water vapour and an upward movement of a i r masses a r e characterized by frequent p r e c i p i t p t i o n . The important influence of a r e g i o n ' s l a t i t u d e on the r a i n f a l l frequency i s evident : (a)

t h e e q u a t o r i a l zone has the h i g h e s t annual p r e c i p i t a t i o n on average

(50%of the global r a i n f a l l occurs between 20' N.L. and 2 0 ' S.L.), (b) a r e a s which have considerable r a i n f a l l cover middle and higher l a t i tudes, oceans and the western p a r t s of c o n t i n e n t s , (c)

a r e a s with p a s s a t winds and s t r i p s along the t r o p i c s a r e r a i n l e s s .

(d) p o l a r a r e a s a r e a l s o r a i n l e s s , obtaining 4 % of the t o t a l global precip i ta t ion. I n c e r t a i n c l i m t i c regions, p r e c i p i t a t i o n and i t s s t a t e of aggregation depends t o a g r e a t e x t e n t on the a l t i t u d e (Fig. 1 . 8 ) . The increment i n the r a i n f a l l t o t a l , corresponding t o the d i f f e r e n c e i n a l t i t u d e , is the r a i n f a l l gradient. Local f a c t o r s which influence the s p a t i a l d i s t r i b u t i o n of r a i n f a l l include geographical and morphological f a c t o r s , such a s t h e area exposure ( t o the d i r e c t i o n of wind), the c h a r a c t e r i s t i c of i t s surface (roughness, vegetative canopy), and the g r a d i e n t of the slope. R a i n f a l l i n t e n s i t y , very o f t e n unevenly d i s t r i b u t e d i n space and time, decreases on average with the a r e a s a f f e c t e d and with the r a i n f a l l duration. The unevenness of the space-time d i s t r i b u t i o n of the r a i n f a l l r e s u l t s i n a f l u c t u a t i o n of p r e c i p i t a t i o n during the year and i n a

21 f l u c t u a t i o n of annual average. Diiring periods of d e f f i c i e n t p r e c i p i t a t i o n the deviation from average i s g r e a t e r f o r r i v e r runoff than f o r r a i n f a l l . The complicated mechanism of p r e c i p i t a t i o n can be influenced i n p a r t i c u l a r by

-

changes i n the h e a t i n p u t , changes i n the a i r mass movement, increasing o r decreasing t h e q u a n t i t y of condensation nuclei.

The r e s u l t of any of these measures i s n o t e x p l i c i t , because the r e l e v a n t i n t e r r e l a t i o n s h i p s of the atmospheric sys tem a r e complicated And zi c e r t a i n feedback e x i s t s , such a s the atmospheric system's external re1at;ons with the hydro- and l i t h o s p h e r e and t h e s o l a r system, whose energy supply i s n o t uniform.

1 . 3 . 3 Interception I n t e r c e p t i o n is a process of p r e c i p i t a t i o n transmission and r e d i s t r i b u t i o n on the boundary of t h e systems of t h e atmosphere and the lithosphere by t h e vegetative canopy. The q u a n t i t y of p r e c i p i t a t i o n which a c t u a l l y reaches the ground, e f f e c t i v e rain- and snowfall, c o n s i s t s of t h e - throughfall , which reaches the ground d i r e c t l y through intershrub spaces and drips from t h e leaves, twigs and stems, and of the - stemflow which reaches the ground by running dawn the stems. I n t e r c e p t i o n loss i s the p a r t of p r e c i p i t a t i o n r e t a i n e d by the vegetative canopy and then evaporated o r absorbed. Therefore

(W

P =P-I F e P

I

- net

precipitation

- actual precipitation - i n t e r c e p t i o n loss

(above t h e v e g e t a t i v e canopy)

(m)

I = I1 + I2 I1

- i n t e r c e p t i o n by

I2

-

S

(1.26)

the z e r i a l portion of the vegetative canopy

i n t e r c e p t i o n of t h e l a y e r of shedded leaves and needles

(1.27)

Pe = T + S - I 2 T

(1.25)

- throughfall - stemflow I n t e r c e p t i o n loss during one s i n g l e r a i n f a l l c o n s i s t s of t h e i n t e r c e p t i o n

capacity of the surface of l e a v e s , twigs etc. and the amount evaporated and absorbed by p l a n t s : (1.28)

I =. I + Iea I.

- interception

capacity of leaves, twigs e t c .

22 Iea

- i n t e r c e p t i o n loss by evaporation and absorption

Absorption of water by p l a n t s during one s i n g l e r a i n f a l l is n e g l i g i b l e . For t h i s reason Linsley derives the following equation f o r t h e i n t e r c e p t i o n during one s i n g l e r a i n f a l l : 1 = 1+

d . E T . t

(m)

(1.29)

d - r a t i o of t h e t o t a l evapotranspiration and the evaporation from t h e vegeta-

t i o n s u r f a c e , depending on the r a t i o of the vegetative and non-vegetative surface

FT t

(s-l)

- evapotranspiration - r a i n f a l l duration The i n t e r c e p t i o n capacity depends on the composition of the r e l e v a n t l e v e l s

of t h e v e g e t a t i v e canopy, i t s morphology arid development s t a g e . This c a p a c i t y , which can be reduiced by preceding r a i n f a l l , influences the n e t p r e c i p i t a t i o n i n dependence upon the a c t u a l r a i n f a l l iritensi t:y, duration and ccurse a s weJ.1 a s upon the wind v e l o c i t y . An o v e r f u l f i l i i n g of t h i s int.erception capacity is c h a r a c t e r i z e d by a remarkable i n c r e a s e of s ternflow and throughfall (dripping). It goes wj. thout saying t h a t the intierception loss nuy exceed the i riterception 1 capac ipy. ZinLe (1967) e s t i m a t e s , without including c.he capacity o€ the shedcled leaves

and needles, the average i n t e r c e p t i o n capacity of nmst g r a s s e s , t r e e s and shrubs a t 1.3 mn during one s i n g l e r a i n f a l l and 3.8 mn during snowfall. He a l s o s t a t e s t h a t the i n t e r c e p t i o n loss is twice a s high i n 20% of t h e observed cases. The average i n t e r c e p t i o n l o s s of a c e r t a i n a r e a depends n o t only on the compos i t i o n of the v e g e t a t i v e canopy, i t s development s t a g e and a c t u a l state, but a l s o on t h e t i m e d i s t r i b u t i o n of t h e p r e c i p i t a t i m and the i n t e r p l a y of the r a i n f a l l occurrence with the course of temperature, humidity and wind v e l o c i t y . Depression and Detention Storage; Overland Flow 1.3.4 The e f f e c t i v e p r e c i p i t a t i o n reaching the e a r t h ' s s u r f a c e is p a r t l y s t o r e d ( a ) a f t e r snowfall a s snmpack, whose f u r t h e r e f f e c t on runoff depends on energy supply, i . e . on

-

r a d i a n t hea.t frcm the sun l a t e n t h e a t of vaporization released by t h e condensation of water vapour,

(b) by depression s t o r a g e i n s u r f a c e puddles and by s u r f a c e d e t e n t i o n formed by a s h e e t of water on t h e s o i l s u r f a c e . ( c ) a s channel s t o r a g e i n stream channels, ponds, swamps, e t c . Depression s t o r a g e i s n o t d i r e c t l y measurable and even d e t e n t i o n s t o r a g e is usually derived from hydrograph a n a l y s i s r a t h e r than from observation. Surface

23 runoff usually c m e n c e s from one part of a catchment area before the interception and depression storages i.n other p a r t s a r e s a t i s f i e d . Detention storage depends on the slope and surface roughness of the area, i . e . on the s o i l conditions, the vegetative cover and i t s s t a t e . The difference between types of vegetation a r e caused by the e f f e c t s of the l i t t e r , which appears to be more s i m i . f i c a n t than i r r e g u l a r i t i e s i n the s o i l surface. The surface runoff does not occur whenever the rai.nfa11 i n t e n s i t y does not exceed the i n f i l t r a t i o n and evaporation inter1si.Q. I n t h i s case t.he sur€ace runoff does not occix oiily during the f i r s t p a r t of the storm, when the interception, depression and detention storage capacities a r e not exceeded. As the rain continues, puddles become f u l l and the s o i l surface becomes covered with a sheet of water and downhill flow begins towards an established surface channel. A level p l a i n can a c c m u l a t e 3-18 m of water, meadows and f i e l d s 12-42 mn and f o r e s t s much more water, which gradually i n f i l t r a t e s and evaporates. when these limits a r e exceeded, spa t i a l l y varied unsteady flow during r a i n f a l l occurs, i n which the r a t e and depth of flow increase dawn the length of the flow path. This depth a l s o increases with time, even when the i n t e n s i t y of the r a i n f a l l renairis unchanged. For these conditions the r e l a tionship becomes D e = R . L . q De L q K

- volume of - length of

(1.30) detention when equilibrium flow condition is established (m3) flow

(m) (m 3 .s -1)

- discharge per meter width a t equilibrium - c o e f f i c i e n t of

r a i n f a l l i n t e n s i t y , slope and roughness of the surface

Where steady uniform overland flow i s considered (Tab. 1.5), the following relationship between r a t e of discharge and depth of overland flow can be theoret ica 1ly derived: Q = K . H m Q

H

m

-

(m2. s-l)

overland flow depth of flow

- c o e f f i c i e n t of

(m’.

s-l)

(m) slope and roughness (involving v i s c o s i t y ,

m = 3 f o r laminar flow, m = 1.67 f o r turbulent flow)

1.3.5

Infiltration

I n f i l t r a t i o n is a process of unsaturated o r saturated flow during the movement of water i n t o the pedo- and lithosphere, detructing the s o i l water and groundwater from the n e t p r e c i p i t a t i o n . Water t r i e s t o achieve a s t a t e of minimmn energy i n these systems and moves from levels of higher energy to levels of

24 1mer energy. Saturation depends on the porosity of s o i l o r rock and the moisture content. When the moisture content i s smaller than the porosity, the flow i s unsaturated. \ h e n it equals the porosity, the flow i s saturated. I t s r a t e depends on the e f f e c t i v e porosity, which i s usually expressed a s a percentage and defined by

(1.30) n

-

Vv

- volume

Vo

-

e f f e c t i v e porosity

(%)

of water governed by gravity forces i n the saturated s o i l o r rock ( i . e . the volume of a l l connected e f f e c t i v e pores and voids) (m3)

t o t a l volume of the s o i l o r rock (the volume of a l l pores and voids plus the volume of a l l the grains and s o l i d s ) (m3)

The e f f e c t i v e porosity i s a p a r t of the t o t a l porosity which enables the g r a v i t a t i o n a l movement of water. I t depends on s o i l texture and s t r u c t u r e (grain-size d i s t r i b u t i o n , mutually connected pores and cracks e t c . ) I n f i l t r a tion a l s o depends on the s t a t e of the s o i l surface i n c l . density of vegetation, moisture d i s t r i b u t i o n i n the s o i l layer, the a i r content i n non-capil lary pores, the temperature, the depth of the groundwater table and the i n t e n s i t y of the r a i n f a l l (high i n t e n s i t y r a i n f a l l causing compaction of the suirface l e v e l ) . The i n f i l t r a t i o n r a t e i s the maxirnun r a t e a t which the s o i l can absorb prec i p i t a t i o n i n a given condition. The i n i t i a l high r a t e of i n f i l t r a t i o n decreases exponentially: rapidly a t the beginning and then more slowly u n t i l i t approaches a constant r a t e a f t e r a period of 20 t o 120 minutes. P h i l i p (1958) expresses the a c t u a l i n f i l t r a t i o n r a t e by the formula

(1.33)

- actual infiltration rate s - sorptivity t - time of the beginning of vi

vk

(m.s-l) (m.s> imfiltration

- final stable infiltration rate

(s) (m.s-l>

S o r p t i v i t y can be defined by the equation

s* = k;

2 k;.

(%+

H)

- coefficien of k f 6 W5

. (Wo - W i )

(1.34)

the hydraulic (unsaturated) conductivity

(m. s-l) JT

- soil c h a r a c t e r i s t i c

(m>

(1.35)

25 Wo Wi

H

- f i n a l moisture content - moisture content a t t h e beginning - depth of groundwater t a b l e

(3

(m)

P h i l i p (1969) expresses the total value of i n f i l t r a t i o n by the sequence i n which the f i r s t two component p r e v a i l N n = S . tS +

Wn

V k .

- infiltration

t

total

(m)

(1.36)

(m)

The following prlicesses of unsaturated subsurface flow a r e interconnected with the i n f i l t r a t i o n r e d i s t r i b u t i o n , when s o i l water e n t e r s the layers with lower moisture con-

-

tent, percolation, when water leaves the s a t u r a t e d s o i l layers and e n t e r s the

-

groundwater , c a p i l l a r y r i s e , when the nmisture of the upper layers is supplemented from

-

the lmer ones, o r from the groundwater.

1.3.6 Subsurface Water Movements Subsurface water forms the subsurface hydrosphere i n the heterogeneous environment of the s o i l and hydrogeological s t r u c t u r e s , which occurs i n d i f f e r e n t forms (Tab. 1:5). The subsurface hydrosphere is fomed by: - s o i l water, occurring i n the upper 2-4 m layer on the boundary of the atnosphere and the lithosphere. Water is r e t a i n e d i n s o i l by surface-tension forces, which a r e molecular ( e l e c t r i c a l ) by n a t u r e , i . e . o t h e r than those of gravity. The outflow of f r e e water from s o i l s occurs only i f the pressure i n the s o i l water exceeds the atmospheric pressure. S o i l water i s , therefore, uns u i t a b l e f o r water e x t r a c t i o n , b u t indispensable f o r the photosynthesis of a l l plants.

-

groundwater i n t h e perineab1.e formations of t h e E a r t h ' s crust., retained especially by g r a v i t a t i o n a l forces and, t h e r e f o r e , usable f o r e x t r a c t i o n (Fig.

1.8). Perfieable geological formations a r e k n a a a s aqui.fers and water occurs i n t h e i r i n t e r n a l void space, forming ( a ) voids o r pores i . e . s u b t l e , microscopic spaces, which originated simultaneously with the a s s o c i a t e d rocks , (b) cracks , i . e . breaches and o t h e r g e n e r a l l y multi-directional spaces of secondary, t e c t o n i c o r i g i n , ( c ) c a v i t i e s , o r spaces of exceptional dimensions, o r i g i n a t i n g mainly i n cars t i c formations.

26 TABLE 1.5 FOm c

Prevailing forces

Occurrence

Flovenient

Water vapour

pressure

gaseous s t a t e

by pressure g r a d i e n t , wind power

I c e , snow

gravity

by ~ g r a v i t y ,i n s o i l a f t e r h e a t input by g r a v i t y and tidal f o r c e s , earth surface, p o r e s ? f r a c t u r e s , p r e s s u r e , o s m t i c acd tern perature madient camties

Gravi tat iona 1 g r a v i t y

s o l i d state

Capillary

surface tens ion

-

Adsorbed

attractive (surface potential)

hygroscopic viscous

overrdrying a t 105°C

Structural

rno l e c u l a r

crystal1 ic chemically combined biological

a f t e r disintegration/integration

biochemical

suspended held i n the interstices, supported available for plants no c o n t a c t with gravitational

a f t e r disintegration

Modes of water occurrence above and under the ground.

TABLE I .6 Types of i n t e r s t i c e s

fractures-cavities

Graphical i n t e r p r e t a t i o n

-

x zc

11-

Categorization of combined permeability according t o Landa (1980)

I

27 P a r t of the water i n f i l t r a t e d i n t o the s o i l flows l a t e r a l l y a t shallow depths as interflow owing t o less pervious lenses below the s o i l surface.

Fig. 1.8. Schenatic r e p r e s e n t a t i o n of a c h a r a c t e r i s t i c arrangement of groundwater s t r a t a . (1) 1st (unconfined) aquifer, ( 2 ) depends on geographical length and geological s t r u c t u r e . The s i z e of c i r c l e s i s proportional t o the pressure (potential). Voids, cracks and c a v i t i e s form extremely complicated underground spaces, which a r e separated o r interconnected and which comnunicate e f f e c t i v e l y o r none f f e c t i v e l y . Water i n these i n t e r n a l spaces, whose permeability is combined (Tab, 1,6), i s influenced by

28

- acting a s

(a) gravity - acting as the water weight, surrounding geological f o m t i o n s ,

the pressure of

(b)

pressure of gases emitted by the water

( c)

surface-tension forces ( c a p i l l a r i t y ) molecular forces of the s o i l or rock p a r t i c l e s (hygrosc0pi.c forces e t c . ,

(d) primarily e l e c t r i c a l in nature) (e) osmotic forces, caused by the different qualilry (chemical composition) of water i n different parts of the geological. formations. Unless these forces are i.n a s t a t e of equilibrium, groundwater is in movement and a l s o influenced by ( f ) f r i c t i o n forces, caused by the roughness of the surface of the s o i l or rock p a r t i c l e s , (g) internal f r i c t i o n forces caused by the fluid viscosity. The flow in mutually comnunicating voids, cracks and cavities is i n d e t a i l non-unifoxm and unsteady. For practical purposes i t can be considered as uniform and steady on average. For groundwater movement Darcy's law i s applicable within the l.aminar range of flow where r e s i s t i v e forces govern flow and the s o i l /rock envirmment i s saturated Vf

(m.s-1 , m per day)

= g = k f . I

Q

- apparent velocity - flow r a t e

A

-

cross-sectional r a t e

I

=

dh ar; - hydraulic

kf

- coefficient

vf

(1.37) t

of f l o w

(m3 .s -1 , m3 per day)

gradient

of hydraulic conductivity (Tab. 3.6)

As velocity increases, i n e r t i a l forces change the linear relation to the apparent. velocity of flow a t the hydraulic gradient to the

1

L

vf=kf. I m m

- coefficient

-1

,m

per day)

(1.38)

(m.s -1 , m per day)

(l.39)

(m.s -+2

Similar equations can be derived for unsaturated flow

vf =

- Kf . g r a d y

grad?

ki

- gradient

- coefficient

of the t o t a l potential of the groundwater

of the unsaturated flow

(m.s-1 )

29 TABLE 1 . 6

Soil

C o e f f i c i e n t of hydraulic conduc-

Capillarity

t i v i t y k f (m.s-')

(nm)

Average poros i t y

2000

-

4000

50

-

95

5.10-6 -

700

-

1500

40

-

60

Compacted loamy sand

1 - 5.10-6

350

-

700

15

- 25

Fine and loose sand

1

5.10+

50

-

350

20

Coarse sand

1-

s.~o-~

10

50

25

Sandy gravel

2 . 1 0 - ~ - 1.10-~

-

- 45 - 35

20

-

1.

-

25

- 35

Clay

1.10-8

Silt

Clean gravel

-

40

Coefficients of hydraulic conductivity and average porosity and c a p i l l a r i t y of different soils. The t o t a l p o t e n t i a l of t h e groundwater i s the amount of energy needed t o

t r a n s f e r a u n i t of water q u a n t i t y from one place i n the system water-rock/soil I

to another one:

?'= t y k =y k . Fk

2 s-2 (J .kg-l = m )

. dl

.

-

t o t a l p o t e n t i a l of water i n tht. force f i e l d

(J.kg-')

Fk

-

u n i t force of t h e force f i e l d

(N. kg-l )

dl

-

distance

(1.&0)

O n the b a s i s of the d e f i n i t i o n s and formulas i n Tab. 1 . 7 , the t o t a l p o t e n t i a l

of groundwater under isothermic conditions is

Y'= g .

(x+z) +

1 d"'

(4P

-6 )

(J.kg-')

(1.41)

The groundwater mvement is s p a t i a l i n c h a r a c t e r . Depending on the governing p o t e n t i a l , the regime of flow can be

- where g r a v i t a t i o n a l and pneumatic forces a r e governing, - where t h e d i f f e r e n c e i n temperature is governing, hydrochemical - where osmotic forces a r e governing.

(a) hydrodynamic

(b)

hydrothermal

(c) The hierarchy of these groundwater movement regimes is interconnected with

the values of the a s s o c i a t e d p o t e n t i a l s , which used t o be remarkably d i f f e r e n t . The regime of groundwater flow depends on t h e homogeneity of the geological formations. The r a t i o of permeability of the r e l e v a n t formations and t h e i r

30 i n t e g r a t e d p a r t s influences the c r e a t i o n of the flow regime. Several regimes e . g . local, a r e a l and r e g i o n a l , can occur i n a heterogeneous environment (Fig. 1 . 9 ) . TABLE 1 . 7

Symbol

% rc

P'

Potential

Forces

Equation

gravita-

gravity

Y =g.dz

Explanatory notes =

g.z

g

-

z x

-

g

tional capillary

capillarity

Yc= g.x

pneurra t i c

pressure gradient of s o i l pases, atmospheric

qp=

k.3. d l

-_ -b' A P

=

gravitational constant head (m) c a p i l l a r y rise

r- u n i t weight

of

water

(kg.m -3) AP- pressure Eradient

(Pa = kg.rn-l.s-l)

yt

thermic

osmotic YO

wa tc?r dens i ty gradient d i f t erence i n chemical compos i t ion

Y

=

1 .AT

=

1r .J

t r

O

AT- tempera turc gradient

6- o s m t i c pressure (Pa)

Categpol-ization of' s o i i water p o t e n t i a l . The function of d i f f e r e n t forces i n the heterogeneous system of hydrogeologic a l formations depends on e x t e r n a l f a c t o r s , incluaing

-

c l i m t i c and meteorological f a c t o r s ,

-

\ r , r k t i o n s and o s c i l l a t i o n s i n the interconnected surface water levels of

s u r f a c e rim-off,

water courses, r e s e r v o i r s , lakes and s e a s , e x t e r n a l load. Where the s u r f a c e water is not i n contact with an unconfined a q u i f e r , the

-

p r e c i p i t a t i o n produces the gwerning iafluence. Seasonal v a r i a t i o n s i n r a i n f a l l and changes of groundwater i n s t o r a g e , m n i f e s t a t e d by changes i n groundwater t a b l e s , a r e c l o s e l y c o r r e l a t e d . This c o r r e l a t i o n is heavily influenced by the surface run-off:

the groundwater recharge depends on the r a i n f a l l i n t e n s i t y and

d i s t r i b u t i o n . The same monthly averages may produce d i f f e r e n t f l u c t u a t i o n s i n the water t a b l e .

31

0 -15

n - , 0

0.45

0.25

0.35

0.45

a.

0.55 0.65 t.

0.75

0.85

0.95

Fig. 1.9. Regional flow of groundwater (flow d i r e c t i o n marked f u l l y , equipotent i a l s dashed, system boundaries dash- and d o t t e d ) : a - hcmegeneous permeable s t r a t a according t o llubbert (1940), b - homogeneous i s o t r o p i c s t r a t a according to Toth (1962), c - heterogeneous s t r a t a according t o Freeze, Witherspoon (1966): local regimen dotted densely, intermediate medium, regional regimen dotted scarcely.

b. 5

h m (mm)

0.4

0.3

0.2 0.1 n

4920

1900

1940

1st WEEK

2nd WEEK

3rd WEEK

4thWEEK

Fig. 1.10. Reduction of values and t i m e delay of groundwater f l u c t u a t i o n i n rel a t i o n t o the r a i n f a l l occurrence ( d e v i a t i o n from the average) according t o Todd (1970). Relationship of the a i r pressure and the water t a b l e f l u c t u a t i o n i n an a r t e s i a n well according t o Robinson (1939). Atmospheric pressure has no e f f e c t on unconfined a q u i f e r s . I n the case of confined a q u i f e r s , increases i n atmospheric pressure cause a decrease i n water tables and v i c e versa (Fig. 1.10): Ah =

?.Apa

(m)

Apa

- change

i n atmospheric pressure

Ah

- water

level decrease or increase

(m of water)

(1.42)

32 1.3.7

Flow i n Channel Network

Overland flow i s eradiial~lvconcentrated by t h e topography o f t h e E a r t h ' s

siir

f a c e . Flow i n n a t u r a l channels whose p r o f i l e and head i s n o t s t a b l e due t o erosion and s i l t a t i o n is g e n e r a l l y non-uniform and tinsteady. The discharge and the medium averape v e l o c i t y a r e fimctions o f t i m e and space. The discharge i n n a t u r a l channels can f o r p r a c t i c a l . piirposes be considered a s gradually v a r i e d . In t h i s c a s e , the t o t a l head Ah a t n channel s e c t i o n can be expressed a s Ah

v:

.

I,

=

.

2 2 (v, - v l )

n

-+

= v1

k (1.43)

R v

.

2g

Rf +

"2

=

2

"2g.

Ah+k(vy

-

v;)]~

(m.s-')

& - t o t a l head a t a channel s e c t i o n

(m)

v I , v2 - mean v e l o c i t y i n t h e upper and lower p r o f i l e

T2 - length of t h e channel s e c t i o n

R - hydraulic r a d i u s ( A

(1.44)

m . n

=

A

-0

)

(m.s-l)

(m) (m)

- a r e a of t h e c r o s s s e c t i o n

(m2)

0 - wetted perimeter

(mi

k

-

n

- c o e f f i c i e n t of channel roughness ( s m o t h 0 , 0 1 , v a r i a b l e s e c t i o n s 0,05)

reduction c o e f f i c i e n t (

1 )

Under conditions o f a s t a b l e p r o f i l e , uniform s l o p e and roughness i n a channel without b a r r i e r s , t h e equation (1.43) can be s i m p l i f i e d a s follows v s = -n1.

I

R4

(m.2-l)

(1.45)

Ah - s l o p e of t h e channel

= -T;

The roughness c o e f f i c i e n t depends on geomorphological condi tioris: t h e riverbpd m t e r i a l , t h e unevenness of i t s s u r f a c e , t h e c h a r a c t e r of the p r o f i l e changes, t h e b a r r i e r s i n t h e r i v e r b e d , t h e r i v e r s i d e vegetatior., t h e meandering and sediment t r a n s p o r t (Tab. 1.8). The total roughness c o e f f i c i e n t can be a s s e s s e d on t h e b a s i s of t h e sripp1e~ientedforrrmla of Cowan (1957) n = m . s .

4

k=l "k

(1.46)

33 TABIE 1.8

Coefficient of

characteristics

Value

Coefficient of

Characteristics

Value

earth rock f i n e gravel coarse gravel

0,020

n4

"1 rmterial roughness

negligible small medium high

0,000-0,010 0,010-0,015 0,020-0,030 0,040-0,060

smooth, p l a i n smi11 r i p p l e s medium r i p p l e s dunes

0,000 0,005

lOW

"2 bed roiighnes s

0,005-0,010 0,010-0,02 5 0,025 ,0,050 0,050,0,100

"3 cross section changes

barriers

gentle o c c , ~iorlal s frequent

:):it

n5 vegetation canopy

0,WO

m

high medium

high and dense

mpandering

laJ medium high

1,000 1,150 1,300

low high muddy discharge

1.000 1 500

-0,015

S

sediment transport

; 2 -

100

P a r t i a l c o e f f i c i e n t f o r estimation of the roughness c o e f f i c i e n t f o r various boundaries according t o Cowan (1957) supplemented by t h e c o e f f i c i e n t of the sediment t r a n s p o r t impact. 1.4

INTERREIATIONS OF SLJRFACF WATER AND GROllNJWATER RLTNOFF

Runoff is a hydrologic process of r a i n f a l l d i s t r i b u t i o n by the E a r t h ' s sinface, which takes place i n thc system of the l i t h o - and hydrosphere. This system c o n s i s t s of n a t u r a l (m~r?tiological, geological, s o i l , vegetative) and anthropogenetic elements (urban, r u r a l and o t h e r c o n s t r u c t i o n s , dykes, r e s e r v o i r s , drainage and sewerage networks e t c . ) . The output of t h i s system depends on the input, which i s characterized by ( a ) meteorological data, e s p e c i a l l y r a i n f a l l d i s t r i b u t i o n ( b ) climatological data, or t h e supply of s o l a r energy, and on the a c t u a l s t a t e of t h i s s y s t e n , which depends on i t s previous function (degree of s a t u r a t i o n ) and anthropogenetic f a c t o r s (water management a c t i v i t i e s ) . Under n a t u r a l undisturbed condj t i o n s , the s u r f a c e outflow can be characterized by meteorological and cl irratological f a c t o r s (Tab. 1.9). Surface runoff equals p r e c i p i t a t i o n minus i n t e r c e p t i o n , depression and detention s t o r a g e , changing i n t o i n f i l t r a t i o n and evaporation. The r a t i o of the sur-

34 TABLE 1 . 9

Category

Area ( c l i m t e f

Sub-category

C h a r a c t e r i s t i c s of discharge occurrence

1.

discharges only i n r a i n f a l l periods

2.

high 6 is charges i n w i n t e r , extremely law i n suniner

t r o p i c a l and subtropical

3.

high discharges during sunmer

humid

4.

high discharges o u t of the sulmer season

cool humid

1.

peak discharges e s p e c i a l l y i n s p r i n g , influenced by r a i n f a l l

Rivers whose f l m depends

hilly, nor t h e m

2.

high discharpes influenced by r a i r fall

mainly on snowmelt and

high mountains

3.

high discharges from snowmelt i n smer

g l a c i e r runoff

pemfros

4.

temporary s treans downstream of glaciers

a r i d and semiarid

A. Rivers whose depends mainly on r a i n f a 11

B.

Categorization of r i v e r s according to meteorological and climatological f a c t o r s . I

TABLE 1.10 Type of a r e a

Slope f l a t 'average 1% 1-5%

Residential

closed blocks paved courts

Apparment dwe 11i n g

closed blocks with yards open blocks detached m l t i - u n i t s

0.70 0.60 0.50

steep

5% 0.90

0.40

0.80 0.70 0.60 0.50 0.40 0.30

0.50 0.40

0.90 0.50

-

Single-family houses with gardens

attached detached

0.30 0.20

Industrial

o l d type densely covered modern wi.th laws

0.60 0.40

0.80 0.70 0.60

~~

0.30 0.80 0.95 Railway a r e a s 0.30 0.40 Unimproved a r e a s 0.20 0.30 Grassland, f i e l d s sandy s o i l 0.05 0.10 0.15 0.17 0.22 0.35 heavy s o i l Forests 0.00 0.05 0.10 Values of runoff c o e f f i c i e n t i n r e l a t i o n t o the type of the drainage a r e a . Parks, cemeteries, playgrounds S t r e e t s , d r i v e s , walks , roofs

0.10 0.70 G.20 0.10

0.20

35 face runoff and t o t a l l o s s i s (recharge and evaporation) does n o t change when the s t a t e of t h e elements and t h e energy supply i n t o t h e system remains c onsta nt. For p r a c t i c a l reasons t h i s r a t i o i s considered a s s t a b l e even i n the case of a

s i n g l e r a i n f a l l . Such hypothesis leads t o the lollowing sim plifie d equations f o r each of the elements Q . = P . s1 g1

j:

- (I.1 + D.) = P. 1 1

(Kai

+ Ei)

(3

(1.47)

(1.48) and f o r the t o t a l a r e a n 5 c;

. Pi . Ai

Qs

=

1000.

Qs

-

s u r f a c e outflcw

(1.49)

(m3)

G - groundwa t e r / s o i l recharge

(m3 )

Pi - p r e c i p i t a t i o n i n element i

(m)

a

Ci

-

Ai

- area

runnoff c o e f f i c i e n t of element of e l eiaent

(IJ,

This s i m p l i f i c a t i o n n eg l ect s the time d i s t r i b u t i o n of tlle input data and the changing state of t h e runoff system. The a c t u a l runoff c o e f f i c i e n t is not s t a b l e . i t is not only a f u n ct i o n of t h e drainage a r e a roughness r (which chaiiges e . g . with t h e s e a s o n ) , i t s shape and s l o p e i , geology g but also a function of the soil state

Factors r , i , and g a r e r e l a t i v e l y s t a b l e and a r e almost independent of m e t e o r o l o g i a l conditions. r a c t o r sf depends on f r o s t an6 s a t u r a t i o n of s o i l . I t determines the a c t u a l runoff j n t h e s p e c i f i c hydrologic s i t u a t i o n . The t o t a l annual runoff can be determined on the b a s i s of the c lim a toloa ic a l input d a t a . Data en the l e f t s i d e of t h e s i m p l i f i e d equation o i the hydrologic balance i . e . p r e c i p i t a t i o n P and s u r f ace runoff Q

= G + E

P-Q

S

P

(m,m3 per ye a r)

(1.51)

can be measured q u i t e e a s i l y and p r e c i s e l y . They a r e i n mst cases measured i n the long term and s y s t e m a t i c a l l y , and a l s o analyzed statist.ically. Data on evaporation E and groundwater recharge G on the r i g h t sj.de of the equation, a r e 8’ d i f f i c u l t t o m a s u r e and, t h er ef o r e, n o t syste m a tic a lly f o l l m e d up. Groundwater recharge and evaporation can be expressed as a function of the l e f t s i d e o t the

36

equation 1.51 E = f l

(P-C,)

c, = f 2 ( P - 9s ) R

3

)

(1.52)

3 ( m v )

(1.53)

(m,ni

The maximum p o s s i b l e evaporation f o r the measured long-term d i f f e r e n c e of rainf a l l and the s u r f a c e runoff is

Em

3 (m,n )

=P-Qs

(1.54)

I n t h i s case G = 0, the groundwater i s without recharge. g

This phenomenon occurs i n d e s e r t catchment a r e a s , where a l l the i n f i l t r a t e d water evaporates. This can be graphically i l l u s t r a t e d by a s t r a i g h t l i n e with an angle of 4 5 ' (Fig. 1. 11).

E (mm)

I-

/

/

.-----

I

r -

P-Qs

(mm)

Fig. 1.11. Regional c h a r a c t e r i s t i c s of the runoff: E - evaporation, E T 1 - evapor a t i v i t y , P - r a i n f a l l t o t a l , G - groundwater recharge, os - s u r f a c e water runF: off. The second limiting- s t a g e could t h e o r e t i c a l l y be reached when the d i f f e r e n c e

of r a i n f a l l and s u r f a c e runoif recharges t h e groundwater without any ebaporation. This case is g r a p h i c a l l y illustra.ced by the h o r i z o n t a l a x i s . The p r a c t i c a l values of t h e function f l migrate between these two Limiting s t a g e s . They a r e a l s o l i m i t e d by t h e n1value of p o t e n t i a l evaporation corresponding t o the supply of s o l a r energy i n the a r e a . Curves f 1 and f ,2 express t h e average influence of the i n p u t data of the relevant runoff system and can, therefore, be used a s regional c h a r a c t e r i s t i c s f o r the assessment of the

groundwater runoff and evapo-

ration. The system of the r a i n f a l l / r u n o f f process can be modelled on a physical o r mathematical b a s i s . The b a s i s of the mathematical Tank blade1 assembled by

SWAWARA (1974) is hydraulic. This model represents the catchment area by a set

37 of tanks, arranged v e r t i c a l l y i a a row. The number of tanks, t h e i r grouping and conf iguratTon deperta

01: the

ca tclmeiit c h a r a c t e r i s t i c s . Experience shows t h a t

the following two b a s i c systems a r e s u i t a b l e f o r any p r a c t i c a l case (a) (b) areas.

four tanks arranged v e r t i c a l l y f o r humid a r e a s , s e v e r a l rows of four tanks arranged v e r t i c a l l y f o r semi-arid and a r i d

Fig. 1 . 1 2 . Separation of the runoff components, its course and physical principles of the mtheniatical m d e l of t h e runoff process according t o SUGAWAHA (1974): ql - s u r f a c e r u n o f f , % ground s u r f a c e , 93 - intermediate outflow groundwater runoff with short-term and q (above the groundwater t a b l e ) , with long-term delay before p e n 3 r a t i o n i n t o t h e r i v e r , 21 infiltration, 22,23 - p e r c o l a t i o n i n t o groundwater, 24 deep p e r c o l a t i o n . Water tables: hi a t low, h, - a t medim, h 3 - a t high r a i n f a l l .

-

-

-

.

Tanks a r e equipped with s i d e

-

o u t l e t s and bottom o u t l e t s . The outflow from

the s i d e o u t l e t s simulates t h e following components of t h e surface runoff (Fig. 1.12):

-

the top tank the s u r f a c e and ground s u r f a c e r u n o f f , reaching the channel i n

one t o t h r e e days,

-

the second tank the intermediate r u n o f f , reaching the channel i n a week's time.

- the t h i r d and f o u r t h tank t h e groundwater runoff, reaching t h e channel i n one month, o r i n a y e a r ' s time. The top tank generally has two s i d e o u t l e t s , while the o t h e r tanks a r e equipped w i t h one s i d e o u t l e t only. The bottom out1et:s of a l l tanks simulate the i n f i l t r a t i o n o r , i n the case of the f o u r t h tank, the deep percolation. The outf l m from o u t l e t s is simply e w r e s s e d by a l i n e a r o r square r e l a t i o n on the

38 storage amount :

qk

=ak. Xk

qk

-

outflow from the o u t l e t

Xlc

-

s t o r a g e :imunt

4( -

(1.55)

= f,(t)

outlet coefficient

The following simple square r e l a t i o n i s used whenever t h e l i n e a r r e l a t i o n does not generate s a t i s f a c t o r y r e s u l t s : qli =Nk

. Xk2

(m3.s-1)

= "<(t)

(1.56)

'fie nonlinear course of t h e output data is a consequence of a s m r i z a t i o n of the p a r t i a l r e s u l t s :

.

(m3 .s.-1)

k'

(1.57)

r a i n f a l l , not f i l l i n g LIP the top tank up t o the f i r s t . s i d e o u t l e t , does not produce any runoff. Short floods with a r a p i d increase i n discharge) can be modelled more p r e c i s e l y by using more s i d e o u t l e t s i n t h e top tank: The saturat i o n of the s o i l l a y e r can be expressed by a r e s t r i c t i o n of the bottom outflow. Evaporation produces t h e decrease i n the storage amount i n the f i r s t i t a n k . The number of tanks, t h e i r equipment and arrangement r e p r e s e n t the behaviour of the catchment a r e a , This arrangement has t o be

c a l i b r a t e d t o achieve the desired

r e l a t i o n of the input and c o l l e c t e d output d a t a . Catchment a r e a s i n semi-arid and a r i d regions have t o be divided i n t o zones and represented by s e v e r a l rcws of v e r t i c a l l y grouped tanks. Evaporation i n the period without p r e c i p i t a t i o n has t o be

modelled by a space without a n o u t l e t i n

the top tank. Deformations of- the discharge

by ri.ver channels can be nodelled

by s i m i l a r tanks. The 'Tank blodel i s able to extend runoff data series o r to con~pletemissing data by simulation. The most important a c t to achieve the required accuracy is the assessment of mean p r e c i p i t a t i o n : a r e a l f l u c t u a t i o n s i n p r e c i p i t a t i o n a r e

h i g h , both i n s m l l and l a r g e catchment a r e a . Purely m t h e m a t i c a l models of the r a i n f a l l / r u n o f f process can be derived from equations describing the physical substance of t h e hydrological process (Fig. 1.13, 1.14) and t h e hydrologic balance. I r ~ p u tdata f o r such a nodel include r a i n f a l l records, catc'ment and iret:eorological c h a r a c t e r i s t i c s , while the o u t p i t d a t a cover s u r f a c e and groundwater discharges, i . e . e n t r y data f o r t h e erosion

process (Fig. 1.22). Mathemtical simulation models r e q u i r e d e t a i l e d i . n f o m t i o n about nmerous coefficients

(Fig. 1 . 1 4 ) , which i s very seldom a v a i l a b l e i n the p r e c i s e form

39 required. lhese mdels a r e d e t e r m i n i s t i c , b u t a s t o c h a s t i c approach has t o be adapted to m k e tliem function r e l i a b l y .

1

INPUT

precipitation-rain, snow,dew etc,humidity, temperature

I

Fig. 1.13. Schematic r e p r e s e n t a t i o n of t h e model components of the hydrological cycle i n rectangular g r i d : evaporation and canopy i n t e r c e p t i o n model, snarmelt (layered) and oveland flow model (two dimensional), r i v e r flow and r e s e r v o i r operation model, r o o t zone i n f i l t r a t i o n and recharge model (layered, one dimensional unsaturated flow f o r each g r i d element), groundwater model (layered, storage and s a t u r a t e d flow).

40

Fig. 1.14. Mathematical model of the water cycle. Explanation of m i r i equations is given i n t e x t . Outputs of the run-off process form inputs of the erosion process m d e l (Fig. 1.24). SGE - s h e e t / g u l l y e r o s i o n , CHE - channel erosion, R I r e c h a r g e l i n f i l t r a t i o n , A r , A;, A , A f , A - anthropogenetic f a c t o r s . P 1.5

GROUNDWATER LEVEL REGIJIATION, SOIL NISTURE AND SOIL STRUCTIiRE FORMATION

Groundwater flow i n t o s t r e a m s l r e s e r v o i r s , o r v i c e v e r s a , depending on the rel a t i v e a l t i t u d e of the r e l e v a n t water l e v e l s . I n t h i s case of the higher surface water l e v e l , i n f i l t r a t i o n i . e . water supply t o a q u i f e r s occurs. Under conditions of the lower s u r f a c e water l e v e l groundwater which d r a i n s i n t o a stream forms

i t s base flow. Changes i n t h i s regime of i n f i l t r a t i o n o r drainage can occur w i t h time a s stream o r groundwater l e v e l s h i f r (Fig. 1.15). The low r a t e of groundwater flow causes a s h i f t i n time and a reduction i n the values of groundwater t a b l e fluct u a t i o n . The f i l t r a t i o n r e s u l t s i n a gradual improvement of the q u a l i t y of the i n f i l t r a t e d water . The period of progression of the groundwater i n t o the stream channel/reservoir depends on the c o e f f i c i e n t of hydraulic conductivity, e f f e c t i v e p o r o s i t y , distance and head

41 n

. LL (1.58)

>-?+IT

- period

t

of progression

L

-

kf

- coefficient

h

- head

ne

(days)

effective porosity

(%)

s h o r t e s t d i s t a n c e from t h e stream channel (m)

Relationship

of hydraulic co n d u ct i v ity

(m pe r day) (m)

I

Disconnected

1

Mutual

1

Mixed

1

Complicated

Sc he m o t ~c representation (cross section)

hydrogroph

Impact o n

Groundwater o n

depends on the head

depends on the heo

Fig. 1.15. I n t e r r e l a t i o n s h i p s of r u n o f f , water t a b l e s and q u a l i t y of the groundwater. Water t a b l e s : 1 - water course, 2 - independent a q u i f e r , 3 - a q u i f e r dependent on the stream, 4 - confined a q u i f e r ,

The d i r e c t i o n of t h e flow between the s u r f a c e and the groundwater influences the water q u a l i t y : i n t r u d i n g water changes t h e water q u a l i t y of the e f f l u e n t . Both processes, and e s p e c i a l l y i n f i l t r a t i o n , the process of s u r f a c e water penet r a t i o n i n t o the groundwater can be slowed d m by clogging, i . e . the blocking of pores and cracks by suspended matter. During drainage, a re ve rse process occurs, s u f f u s i o n , which g r ad u al l y speeds up the groundwater movement. S o i l moisture, which is of b a s i c importance f o r the water supply of p l a n t s , is less supplemented by groundwater than by p r e c i p i t a t i o n . G ra vita tiona l potent i a l is less important f o r i t s e x p l o i t a t i o n by p l a n t s than the c a p i l l a r y and

42 osmotic f o r c e s , whose function can be measured a s the t o t a l s o i l suction. This t o t a l s o i l s u c t i o n c o n s i s t s of the matric s u c t i o n , numerically equal to the c a p i l l a r y pressure, and the s o l u t e s u c t i o n , numerically equal t o the osmotic pressure. These depend on the s o i l t e x t u r e and s t r u c t u r e , on the interconnection of pores and cracks, on the chemical p r o p e r t i e s and temperature of t h e s o i l and water, but e s p e c i a l l y on the moisture content expressed by the r a t i o w =

- . 100 "W

(7:)

(1.59)

VO

w V

W

V,

- moisture -

content (volumetric)

3 t o t a l volume of water i n pores and voids (m ) t o t a l volume of the rock o r s o i l

<m3)

The r e l a t i o n s h i p of the moisture content and the t o t a l s o i l s u c t i o n has t o be expressed using the n a t u r a l logarithm pF = In of the t o t a l s o i l s u c t i o n = 3 + 981 Pa (m of water)

(1.60)

(Tab. 1.11) TABLE 1.11

Hydrolimits

Full capacity (saturated)

Suction pressure PF

0

Moisture content % 25-60

Definition

I

S t a t e i n which pores and cracks a r e f i l l e d up with g r a v i t a t i o n a l and o t h e r water. Corresponds to the c a p i l l a r y porosity

.

Field capacity FC

2.5-3.0

10-40

S t a t e i n which water is held i n the s o i l a f t e r the g r a v i t a t i o n a l water has drained away.

Point of decreased availability

3.1-3.5

4-35

S t a t e i n which the c a p i l l a r y conductivity was i n t e r r u p t e d .

4.18

2-30

S t a t e i n which evapotranspiration exceeds the water i n p u t (depends a l s o on the p l a n t species).

4.8-5.2

1-15

S t a t e i n which the s o i l does not contain e i t h e r g r a v i t a t i o n a l o r c a p i l l a r y water.

Wilting point wp Adsorption water capacity

Categorization of s o i l state according t o its s u c t i o n pressure and moisture ret e n t i o n from p l a n t c u l t i v a t i o n . The changing s o i l moisture and t h e t o t a l s u c t i o n pressure form c h a r a c t e r i s t i c s i n t e r v a l s . On the boundaries of these i n t e r v a l s t h e water supply of the p l a n t s

43 changes i n a way which q u a l i t a t i v e l y influences the develop,nent of the p l a n t s . The c e n t r e of t h e j e i n t e r v a l s has a c h a r a c t e r i s t i c value of the t o t a l s o i l suc-

t i o n and moisture, depending on t h e s o i l category (Fig. 1.16).

Fig. 1.16. I n t e r r e l a t i o n s of t h e s o i l p o r o s i t y and humidity with the s u c t i o n pressure, p o t e n t i a l and s o i l moisture r e t e n t i o n data according t o Kutilek

(1979). The water regime of s o i l s depends on

-

s o i l category, i t s t e x t u r e , s t r u c t u r e and permeability, c h a r a c t e r i z e d by the

c o e f f i c i e n t of the h y d r a u l i c c o n d u c t i v i t y , o r by the course of the t o t a l s o i l suction, - the p o s i t i o n of the s o i l p r o f i l e w i t h regard t o the groundwater l e v e l and the reach of the c a p i l l a r y zone, - the rcot system of t h e p l a n t s ,

-

anthropogenetic f a c t o r s , i n c l u d i n g e s p e c i a l l y changes i n the s o i l t e x t u r e ,

s t r u c t u r e and moisture during i t s e x p l o i t a t i o n ,

-

climatological characteris t i c s . Rode (1556) c l a s s i f i e s the water regime of s o i l s on t h e b a s i s of the annual

r a t i o of t h e r a i n f a l l and e v a p o t r a n s p i r a t i o n (Tab. 1.12). I t i s u s e f u l to add the swampy regime to t h i s c l a s s i f i c a t i o n , which occurs when t h e water level permanently p e n e t r a t e s above t h e

s o i l s u r f a c e . 'Ihe gradual development of s o i l i s

i n t e r r e l a t e d w i t h t h e water regime and t h e a c t i o n of c l i m a t o l o g i c a l € a c t o r s (Tab. 1.13).

44

TABLE 1.12 Regime

Characteristics

1. Permafrost

The s o i l water is p e m n e n t l y frozen

>1

2 . Flushing

The s o i l is completely wetted s e v e r a l times a year

>1

Ratio of annual precipitation and evaporation total

3. I n t e r m i t t e n t S o i l is not flushed every year

tl

4 . Unflushed

I n f i l t r a t i o n does not recharge groundwater r e s e r v e s , the s o i l p r o f i l e being only p a r t i a l l y wetted

(1

5. Evaporative

S o i l p r o f i l e moisture is supplemented from groundwater

6. I r r i g a t i o n

S o i l r e g u l a r l y wetted by i r r i g a t i o n

<1

P+I_) 7

7 . Marshy

Capillary r i s e permanently reaches the s o i l s u r f a c e , oversaturated by groundwater

Categorization of s o i l water regimes according t o the r a t i o r = annual p r e c i p i t a t i o n t o t a l P and annual mean evaporation t o t a l E Rode (1956). I - annual i r r i g a t i o n r a t e

of the average according t o

TABLE 1.13

Sierozem

a &

3 2

4

&

Chestnut soils

desert soils

Laterite s o i l s

G

E

!? u

6

e

.i

aJ 10 Cd

Podzol s o i l s

$4

Tundra s o i l s

2

.d

P e m f r o st

-c aJ uE) u CdN

Red and yellow podzolic s o i l s

a0

eE

Red-yel low podzolic s o i l s

n o

Podzolic s o i l s

aJ .c

1

-

I

P

-

45

1.6

CLIMATOLOGICAL FUNCTIONS OF WATER

The water cycle is one of t:he basic processes which regulate the climate. The characteristic properties of water which influence the climatic conditions depend on i t s imlecular structure. The climatological regulating functions of water depend on a number of unique physical characteristics: 1-he high value of the specific heat, the high values of the l a t e n t heat of fusion and evaporation, the high coefficient of heat reflectance, the extremely law heat conductivity, and the anomalous density decrease below 4OC, differing from the fusion point (Tab. 1.14).

TABLE 1.14 C l i m t i c impact of water

1. Accumulation and slow transfer of heat

Fundamental cause

.

High s p e c i f i c heat Is = 4.19 103 J.kg.K-' ( a t 2OoC) 4-5 times exceeding that of a i r and rocks High l a t e n t heat of fusion If = 3.55

.

lo5 J.kg-l

(at O ~ C ) High l a t e n t heat of evaporation Ie = 2.26 . l o 6 J.kg-'

2 . Limitation of energy input frcm universe

3 . Limitation of heat

( a t 100°C)

High coefficient of heat reflectance

khr

=

0.582 W.m-l.K-l

radiation 4. Regulation of energy

Low heat conductivity

transfer between the

Fresh water (2OoC) 0.557 w.n~-'.K-~

1i thosphere, hydrosphere and atmsphere

Sea water

5. Influence on temperature

(18OC) 0.561 W.m-l.K-l

Ice 1. I73 W ,m-'. Snaw Highest density a t 4OC

K-I

High s p e c i f i c heat and low heat conductivity

inversion ______~

~~~

6. Influence on microclimate

High specific heat and high l a t e n t heat of fusion and evaporation. I r r e g u l a r i t y of the highest density occurrence ( a t 4OC).

Climatic impact of water and its fundamental causes as a function of i t s exceptional molecular characteris t i c s .

The c o e f f i c i e n t of h e a t r e f l e c t a n c e occurs i n the r e f l e c t a n c e of s o l a r energy and i n t h e h e a t transmissivity of the atmosphere. The Earth r e f l e c t s 34% of the s o l a r energy on average. Two t h i r d s of t h i s value, i . e . 23% of the t o t a l , i s ref l e c t e d by clouds, o r accumulated vapour i n the atmosphere. The increase i n the water vapour pressure leads t o a decrease i n t h e h e a t transniissivity of the a t mosphere. The d i f f e r e n c e between the average values of the h e a t transmissivity of the e q u a t o r i a l and t h e p o l a r zone, with lower h m i i d i t y , exceeds 13%. Water vapour i s the n l a i r i cause of the hot-house e f f e c t of the atrriosphere. I t i n t e r c e p t s i n f r a r e d r a d i a t i o n i n the

sphere of t h e wave length 4 , 4 f i < 2.

<

8,5+

and l l p < I ( 8 0 p . The hot-house e f f e c t of the atmosphere c o n s i s t s i n the input of r a d i a t i o n f r a n the Universe t o t h e Earth with small losses during daytime and i n the output of the h e a t from the l i t h o s p h e r e t o the Universe with high l o s s e s during nighttime. The atmosphere r e t a i n s and r e f l e c t s hack t o the E a r t h ' s surface the i n f r a r e d r a d i a t i o n , forming 66 - 75 % of the r a d i a t e d energy. Carbon dioxide C02 and ozone 0 a l s o take p a r t i n t h i s e f f e c t , but i n a very limited

3

part of the spectrum, t h i s having f a r less influence. Large water formations such a s s e a s , iceberg., , m r s h e s and dambos, r e s e r v o i r s and water courses a c t a s thermal r e g u l a t o r s . Evaporation and t r a n s p i r a t i o n need a l a r g e q u a n t i t y of thermal energy. This energy is released during condensation and accepted by the surrounding a i r , thus causing an equalizing of thermic d i f f e r e n c e s . Due t o the high s p e c i f i c h e a t of water, the process of i t s warming and cooling is slower than the process of the warming and cooling of s o i l . The d i f f e r e n c e s i n winter and sumner temperatures, o r day and night temperatures a r e , t h e r e f o r e , smaller i n t h e v i c i n i t y of water formations. The l o c a l c l k t e is influenced by the thermal i n e r t i a manifested by a slow t r a n s f e r of heat t o the environment. The degree of t h i s influence depends on t h e volune of the functioning water mass and a l s o a c t s over considerable d i s t a n c e s , demonstrated by the c o n t i n e n t a l nature of the climate. Water r e s e r v o i r s , marshes, dambos, snow and ice, a l s o functioning a s runoff r e g u l a t o r s , thus propagate t h i s thermal influence along water courses. The reg u l a t i w function of marshes and damhos q u a l i t a t i v e l y d i f f e r s from the influence of r e s e r v o i r s . Marshes and dambos, containing 80 t o 97% of water, bond on organic m a t t e r . The content of water i n marshes cannot be decreased below 70% by drainage. Evapotranspiration from a marshy a r e a forms 30 - 50%of evaporation from an open water s u r f a c e , n o t taking away a s much energy. Snow and i c e , thermal and runoff r e g u l a t o r s , b a s i c a l l y occur i n two forms (a)

temporary s n m and ice, thawing i n t h e warm season,

(b) permanent snow and i c e , e s p e c i a l l y A n t a r c t i c and Greenland icebergs, sea icebergs and mountain g l a c i e r s , permanent snow , permafrost. P e m n e n t o r perennial i c e and snow occur depending on the climate, a l t i t u d e , l a t i t u d e and morphology. I f the climate is very rigorous, a l a y e r of frozen

47 ground, permafrost, m y be formed, p e r s i s t i n g from y e a r t o y e a r , Thick snowpack tends t o impede the f o m t i o n of permafrost. I n a r e a s where more snow and i c e accumulate than a c t u a l l y m e l t and adjoining areas of luwer a l t i t u d e where t h e wastage of frozen water exceeds i t s accumulat i o n , a sluw movement of snuw and i c e mass from the upper a r e a to the lower one may occur when t h e thickness of the g l a c i e r exceeds 15 t o 30 m. The speed of t h i s mvement depends on the g l a c i e r thickness, i t s temperature and the slope of the ground. I n t h i s way, frozen water is t r a n s f e r r e d t o a r e a s with more favourable conditions for i t s p a r t i c i p a t i o n i n t h e hydrologic cycle ( s e e a l s o Tab. 1.1). The hydrologic and microclimatic influence of snow and p l a c i e r s a l s o functions by means of supplied r i v e r s . Glaciers thaw more slowly than snuw, thus o f f e r i n g high r i v e r discharges before t h e beginning of the s m r season, when i r r i g a t i o n requirements m y be expected t o be h i g h e s t (Tab. 1 . 9 , Tab. 1.15). TABLE 1.15

Season

Albedo

Snowpack thickness

Diurnal f l u c tuation

Runoff

Runoff after rainfall

Longterm storage impact

Sprinz

High

Highest

Slight

Moderate increasing

Subdued delayed

Dry & warm

I

Smer

Moderate

Moderate

High

High

Slight delay

Autumn

Low

Low

Moderate

Moderate

No delay

Winter

Very high

Moderate

Nil

Slight

Stored

years = = Increase i n t o t a l runoff Wet & cool years = =

Decrease i n

t o t a l runoff Seasonal change i n glacier-runoff c h a r a c t e r i s t i c s according t o MEIER (1964). The r e g u l a t i n g functions of water a r e a l s o a consequence of i t s low h e a t cond u c t i v i t y . Heat flaw is the most e f f e c t i v e form of h e a t propagation i n l i q u i d s . Under conditions of r e s t r i c t e d flow below the ice cover, the h e a t l o s s e s of the water formation a r e low. The snowpack has a n extremely low value of the h e a t conductivity. The i n s u l a t i n g c a p a b i l i t y of water therefore appears i n the winter season, remarkably enough, when t h i s is urgently required f o r the maintenance of the temperature of t h e s o i l s u r f a c e . The low h e a t conductivity of the snowpack means t h a t the h e a t output t o the atmosphere does n o t exceed the h e a t i n p u t from the deeper formations. The s o i l temperature below t h e snowpack can be up t o 15OC higher i n comparison t o the temperature of soils without the snowpack. The i n s u l a t i n g e f f e c t of the snowpack

48 does n o t only depend on its thickness, b u t a l s o on the s n m q u a l i t y . The snowpack has a cooling e f f e c t on the a d j o i n i n g , warmer l a y e r of atmosphere, thus causing ground inversion of temperature, e s p e c i a l l y i n t h e s p r i n g season, and a n a s s o c i a t e d increase i n r e l a t i v e humidity. Such inversions above the open water s u r f a c e a r e not a s i n t e n s i v e and occur l e s s o f t e n . The a i r humidity can be characterized by the water vapour pressure. I t s value

-

o s c i l l a t e s between 0 and 40 m i l i b a r s ( 0 4000 Pa) (Fig. 1.17). This pressure decreases with a l t i t u d e : a t 1750 m a . s . 1 . a t one h a l f and a t 5000 rn a t one f i f t h of its o r i g i n a l values a t sea

l e v e l . The content of water vapour i n the atmos-

phere is on average 0.2% i n the p o l a r zone and 2.5% i n r a i n y , t r o p i c a l regions. I t may, l o c a l l y , exceed 4%.

mb

30

20

10

0 0

10

20

*c

Fig. 1.17. Relation between temperature and s a t u r a t i o n vapour pressure above and below O°C. The maximum amount of water vapour i n the a i r depends d i r e c t l y on the temperat u r e . The s t a t e i n which water vapour can e x i s t i n equilibrium with a plane s u r face of l i q u i d water a t the same temperature i s s a t u r a t i o n . The r e l a t i v e humidity is the r a t i o of the a c t u a l vapour pressure t o the s a t u r a t i o n vapour pressure a t the same temperature e u = W . 100

-

(%)

(1.61)

ES

U

-

r e l a t i v e humidity

(Z)

ew

-

a c t u a l water vapour pressure

(mb, 1 mb = 100 Pa)

ES

-

s a t u r a t i o n water vapour pressure

(mb)

The a i r humidity i s continuously changed by evapotranspiration, by the a i r flow and by temperature changes. The dew-point temperature is the temperature t o which the a i r must be cooled a t constant pressure t o reach s a t u r a t i o n with a given water content. Any f u r t h e r decrease i n temperature thus causes condensa-

49 tion, occurring i n d i f f e r e n t forms

of t h e h o r i z o n t a l and v e r t i c a l p r e c i p i t a t i o n

(Fig. 1 . 7 ) depending on the a l t i t u d e , temperature and o t h e r conditions of the environment, e . g . morphology and temperature of the a f f e c t e d surface. The d a i l y minimum of the r e l a t i v e humidity occurs simultaneously with the Q i l y r r a x i m temperature a t constant water vapour pressure. Changes i n the water vapour content i n the atmosphere cause changes i n the r e l a t i v e amounts of the four p r i n c i p a l gases (nitrogen N , oxygen 0, hydrogen H and carbon dioxide CO ) and minute t r a c e s of o t h e r gases, thus influencing i t s physical, chemical

2

and biological c h a r a c t e r i s t i c s . The term drought ( l a c k of r a i n f a l l ) , which negatively a f f e c t s both the l i f e

of m n and the development of p l a n t s , b a s i c a l l y has two d i f f e r e n t connotations: ( a ) c l i m a t i c drought, caused by lack of p r e c i p i t a t i o n o r by i t s inadequate o r i r r e g u l a r occurrence

-

p a r t i c u l a r l y i n t h e growing season o r caused by high

temperature, occassioning extreme evapotranspiration, (b) l o c a l drought, which may a l s o occur i n a r e a s with heavy r a i n f a l l during the growing season, occurring i n regions with permeable s o i l s , where excessive runoff impedes a s u f f i c i e n t water supply of p l a n t s . The degree of the c l i m a t i c drought depends e s p e c i a l l y on the average t o t a l r a i n f a l l o r on i t s r a t i o t o the mean annual temperature (Tab. 1.16). TABLE 1.16

I

C1ima te

Mean annual p r e c i p i ta t i ~ o n t o t a l (m)

Wet Semiarid D r y (steppe and semi-desert)

Extremely dry ( a r i d )

Rainfall factor

r (m/Oc. y e a r )

> 60 40-60 < 40

> 500 400- 500 200- 400 < 200

<( 40

Categorization of climate according t o t h e mean annual p r e c i p i t a t i o n t o t a l and i n r e l a t i o n to t h e r a i n f a l l f a c t o r . Climte is the average cycle of weather c h a r a c t e r i s t i c f o r given a r e a . The

course of humidity and temperature can be

considered a s f a c t o r s which determine

the type of climate. The climate can be categorized according t o the mean annual t o t a l p r e c i p i t a t i o n and i n r e l a t i o n t o t h e r a i n f a l l f a c t o r according t o Koeppen

(1920) (Tab. 1.16, 1.17)

r = PT r

- rainfall

(mn/ factor

OC

. year)

(1.62)

50 P

-

T

- mean annual

annual average p r e c i p i t a t i o n t o t a l

(mm per year)

temperature

(OC>

TABLE 1 . 1 7 Desert

Flora

Steppe

Savanna Prairie

mu,

Jungle

Preva i 1i n g inf hence

RAINY

Equator & tropical wind sys tern

TROPICAL

TROPICAL

35OC

Forest

DRY AND WET

SEMI

MONSOON

Tropical & polar wind sys tern

10°C LATITUDE

ARID

1 I

SDII AE I D

L,5j

Bks

MARITIME

SUMMER

0

COOL SIlMMER

I

ooc

TAX4

r-------- 1

HIGH

1

TUNDRA

I

MOUNTAIN

I

!

-5OOC

Polar & arctic wind sys tern I

0

HumiditybTotal annual r a i n f a l l

41% (40mbar)

Categorization of c l i m t e according t o humidity and mean annual temperature, c h a r a c t e r i s t i c f l o r a and p r e v a i l i n g f a c t o r s of inf h e n c e . Completed according t o the s t r u c t u r e of C r i t c h f i e l d (1960). The r e g u l a t i n g functions of water vapour, i c e , snow and water a c t i n dependance on t h e supply of s o l a r energy, deciding e . g . on the predominant a i r circul a t i o n system. They a r e interconnected with numerous f a c t o r s depending on the l o c a t i o n , e s p e c i a l l y the exposure and a l t i t u d e of the region. The annual and d a i l y amplitude of temperature, upon which the c o n t i n e n t a l i t y of the climate depends, increases with the d i s t a n c e

from oceans. Regional and local morphology, water bodies, s o i l s and v e g e t a t i v e canopy influence the c h a r a c t e r i s t i c s of the meso- and microclimate. 1.7

BIOGEOCHEMICAL CYCLE SYSTEM The mechanical and t h e m 1 energy which water acquires during the hydrological

c y c l e , and i t s chemical energy, i s consumed by (a)

the mechanical and chemical d e s t r u c t i o n o f the land s u r f a c e during rain-

51 f a l l , runoff and weathering, i . e . by h y d r o l y s i s , hydration, dehydration, leaching, dissolving , d i s i n t e g r a t i o n , absorption e t c . , (b) t r a n s p o r t a t i o n and corrosion of sediments,

(c)

deformation of banks and r i v e r b e d s , overcoming of d i f f e r e n t r e s i s t a n c e s during flow and undulation, i n t e r n a l

(d) and external f r i c t i o n , water hammer, ( e ) b i o l o g i c a l processes of p l a n t and animal production,

Water is the widespread agent of e r o s i o n , entrainment, t r a n s p o r t a t i o n and deposition of sediment. The system of these complex processes forms the most important a b i o t i c c y c l e i n t h e environment of t h e water cycle i n the proper sense. I t enables the c i r c u l a t i o n of a n organic and organic compounds of the biogeochemical cycle of elements. This cycle is characterized by a continuous, periodic o r s t o c h a s t i c ( a ) d e s t r u c t i o n and t r a n s f e r of compounds and mixtures of d i f f e r e n t e l e ments, (b)

d i s s o l v i n g , d i s i n t e g r a t i o n and

i n t e g r a t i o n of gaseous, l i q u i d and s o l i d

mineral and organic m a t t e r , ( c ) synthesis of new compounds, a l s o enabling t h e i n i t i a t i o n of new cycles. This cycle regenerates nutriments and thus enables the course of the l i f e process. Only a small p a r t of the stock of elements and t h e i r compunds, e x i s t ing i n the pedo-,

l i t h o - , hydro- and atmosphere, i s activated by the b i o t i c and

a b i o t i c processes and takes p a r t i n the biogeochemical cycle. Erosion i s the process of a c t i v a t i o n . Eroded matter, including bioelements, i.e. elements whose organic compounds form l i v i n g m a t t e r , a r e e n t r a i n e d , transported and deposed a s sediments (Tab. 1.18). TABLE 1.18

Biogeoelemen ts Macrobiogene t i c

Microbiogene t i c

Carbon

C

Calcium

Oxygen Hydrogen

O

Nitrogen Phosphorus Sulphur

Oligobiogenetic ( t r a c e ) Fluorine

F

Vanadium

V

Irov. Fe Alluminium A1 Magnesium Mg Manga,anese Mn

Arsenic

As

Chromium

Cr

Lead

Pb Molybden

Mo

N

Sodium

Na

Iodine

J

T i tan

T i Nickel

Ni

P

Kalium

K

Zinc

Zn

Cesium

cs

S

Chlorine C 1 Copper Boron

Cu B

Selenium

H

Ca

Silicon

Si

Cobalt

CO

Se Galium S troncium S r Vismut

Ga

Rub i d ium Categorization of biogeoelements.

Ru

etc.

Bi

52 Sediments a r e transferred from the higher a l t i t u d e s with less favourable topographical and climatological conditions for cultivation t o l m e r elevations of f e r t i l e plains and more favourable clirrate. The boulders, the gravel and p a r t i a l l y a l s o the sand move near the bottom as bed load. Fine sand and some organic p a r t i c l e s f l o a t a s suspended load; s i l t , clay swim as wash load and trees, plants, leaves a s floating debris (Fig. 1.4). During low floods coarse sediments remain in the channel: inundation contains fine p a r t i c l e s , whose composition and s i z e i s more suitable for the formation of living mtter. Suspended and wash load, partly of organic origin, and floating debris regenerate the bioenergetic potential, i . e . the f e r t i l i t y of s o i l s . During superfloods coarse materials may a l s o enter the flood plain and a f f e c t the s o i l f e r t i l i t y i n a negative way. TABLE 1.19

Continent

Ca tchmen t area m i l .km2

Mean annual sediment transport

t.b-2

Europe A s ia Africa North America South America Aus t r a 1i a

9.3 26.9 19.9 20.7 19.4 5.2

34.8 591.0 27.0 94.6 61.8 44.4

Totallaverage

101.4

198.8

109

Decrease of the land surface during 1000 years

m

0.32

23.2

15.91 0.54 1.96 1.20 0.23

394.0 18.0 63.1 41.2 29.6

20.16

132.5

Annual sediment transport and decrease i n the land surface according to Holeman (1968). I t is a basic prerequisite for intensive agricultural production that the production process should not be interrupted too often by floods and certainly

not a t harvest time. Intensive cultivation develops, therefore, i n areas where the natural processes of inundation and regeneration of nutriments is already a t l e a s t p a r t i a l l y interrupted. Wind erosion returns part of the sedimented matter from dry land t o upper elevations. The greater p a r t accumulates i n seas and reservoirs. It i s p a r t i a l l y absorbed by the biomass. I t a l s o penetrates below the reach of the sun's rays, thus escaping from the biologic cycle. Sediment represent a load on the geological formations of the Earth's crust and thus influence i t s balance. In such a way, they a r e one of the factors which have an impact on volcanic a c t i v i t i e s . New ratter which occurs during volcanic

a c t i v i t i e s on the Earth's surface enters the erosion process and thus closes the biogeochemical cycle. Natural biogeochemical cycles, when not disturbed by human a c t i v i t i e s , a r e with some exceptions almost balanced. They reproduce 90 - 98% of the entering matter, thus maintaining the balance of quantity, s t r u c t u r e and concentration, forming a s t a b l e basis f o r the b i o t i c environment. All organisms conform t o t h i s s t a t e i n the long term. The inequality of the biogeochemical cycle i n the span of geological time leads t o the migration and d i f f e r e n t i a t i o n of species, to dispersion o r concentration of elements and t h e i r compounds i n d i f f e r e n t p a r t s of the region and consequently to the formation of d i f f e r e n t a b i o t i c environments and ecosys tern. An index of element migration, applied by Polynov (1936), i s expressed by the r a t i o of the p e r c e n t a s quantity of the element i n the hydrosphere t o the p e r centage of i t s quantity i n the lithosphere. Kovda (1975) proves on the basis of this index t h a t chlorine C 1 , sulphur S , iodine I , calcium Ca, natrium Na, magnesium Mg, fluorine F, strontium S r , zinc Zn, uranium U and molybdenum M b present high migration, while s i l i c o n S i , potassium K , phosphorus P , baryum Ba, manganese Mn, rubidium Rb, copper Cu, nickel N i , kobalt Co, arsenic As, lithium L i and especially alluminium A 1 and iron Fe present low migration. Divergences occur locally, especially through changes i n the conditions for oxidation or reduction and through the synthesis of integrated compounds.

i

The migration of biogenic elements i s of c r u c i a l importance for the creation and growth of l i v i n g matter. Of the macrobiogenetic elements only phosphorus creates an unbalanced cycle. Anorganic compounds of phosphorus a r e absorbed by plants. They serve a s n u t r i t i o n f o r animals, concentrate f i r s t of a l l i n t h e i r bones and then e n t e r the s o i l i n t h e i r excrements a s well a s a f t e r extinction. I n the course of the erosion process 3-4 m i l . tons of phosphates a r e transported annually t o the sea. Only one t h i r t i e t h of t h i s quantity returns to dry land as a product of fishing, o r as guano e t c . The natural processes supplement its a c t i v e stock i n s u f f i c i e n t l y . The c i r c u l a t i o n of phosphorus is activated by anthropogenetic measures: phosphates a r e a component of most f e r t i l i z e r s a s well as of polluted waters. Blast-furnace s l a g a l s o contains phosphorus. Nevertheless the stock of phosphorus i s gradually diminishing, because t h i s element is absorbed by plants (Fig. 1.18). During the c i r c u l a t i o n of sulphur, bacteria, t h i o b a c i l l i and desulphovibrions a c t i n the s o i l , forming sulphates by oxidation and sulphides by reduction. The s o i l i s enriched with sulphur by means of r a i n f a l l . Organic matter accepts sulphur from the s o i l and surrenders it again during decomposition. The erosion process transports p a r t of the sulphur compounds t o reservoirs and oceans, from which f o m t i o n s sulphur escapes t o the atmosphere i n the form of gaseous c m pounds (Fig. 1.19).

54

Fig. 1.18. Biogeochemical cycle of phosphorus as a subsystem of the hydrological cycle. The unbalanced cycle of phosphorus is controlled by volcanic and biologic a l processes. The amount of carbon dioxide C02 i n the atmosphere is regulated 60% by

oceans and 40% by the photosynthesis of plants. These processes a l s o regenerate the stock of oxygen 0. Carbonates a r e transported during erosion to the sea or enter organic matter from the s o i l . Carbon dioxide escapes from organic m t t e r during respiration, burning, disintegration and from s o i l and water surfaces d i r e c t l y back to the atmosphere (Fig. 1.20). The circulation of oxygen 0, hydrogen H and nitrogen N, whose m i n stock is the atmosphere, i s balanced. Forests, covering 9% of the Earth's surface, produce 48 mld. tons of oxygen annually, i . e . 47% of the t o t a l production. The r e s t is almost completely the share of oceans: the production of rivers and reservoirs

is important from the point of view of meso- and microclimate only. Oxygen and , forming s o i l s , rocks and organic matter take p a r t i n the whole biogeochemical cycle. The nitrogen N i s a component of proteins, thus entering the waste from digestion, extinction and industrial processing. Saprogenic bacteria, acting during decay and a m n i f i c a t i o n , help to create a m i a NH3. Under the action of n i t r i -

hydrogen compounds , such as s a l t s , oxides e t c .

55 ficating bacteria the amonia changes i n t o n i t r i t e s and than n i t r a t e s . Nitrates enter p l a n t matter d i r e c t l y and, p a r t l y by d e n i t r i f i c a t i n g b a c t e r i a , a r e d e c o r posed. Free nitrogen, the r e s u l t of t h i s process, is accepted by the atmosphere (Fig. 1.21). Goldschrnidt (1954) states that 0.75 g-.m-2 of nitrogen enters i n t o the c i r c u l a t i o n i n zones with a mild climate and almost 3 g.m-* i n zones with a humid, tropical climate .

Fig. 1.19. Biogeochemical cycle of sulphur as a subsystem of the hydrological cycle. Fycle of sulphur is activated especially by microorganisms and volcanic a c t i v i t i e s .

9 :

1.7.1 Water Erosion a s a Process Evoked by the Water Cycle The chemical and mechanical energy of wind, i c e , r a i n f a l l , runoff and sediments, a c t i n g during the hydrologic cycle i n the system of the pedo- and lithosphere, r e s u l t s i n the erosion, d i s i n t e g r a t i o n and wearing away of the land (Tab. 1.19). The interplay of a c t i n g forces depending on hydrometeorological factors, geomorphological conditions, namely of - the density and composition of the vegetative cover,

56 - m a t e r i a l and s t r u c t u r e of t h e s u r f a c e l a y e r ,

and o f the d u r at i o n of t h i s process decides on i t s course and form. From t h i s p o i n t of view, i t is p o s s i b l e to d i s t i n g u i s h ( a ) s h e e t er o s i o n - detachment and rerroval of the m a t e r i a l from the e n t i r e land s u r f a c e by wind, r a i n f a l l and overland flow, which may be e i t h e r - s e l e c t i v e and change the s o i l t e x t u r e toge the r w ith the c onte nt of nutriments

i n the soil, o r - s t r a t i f i e d , when the e n t i r e mould l a y e r is washed away,

Fig. 1.20. Biogeochemical cy cl es of carbon and oxygen a s subsyste m of the hydrological cy cl e. The co n t en t of oxygen i n the a t m s p h e r e is mainly c ontrolle d by oceans and by the photosynthesis of t e r r e s t r i a l f l o r a .

(b) pre-channel e r o s i o n , ex er t ed by f orc e s of concentrated pre-channel flow, forming furrows, c u t s , wash-outs, pot-holes and fiullies, ( c ) channel er o s i o n , ex er t ed by f o r ces of concentrated water flow i n stream beds, stream banks and f l m d - p l a i n s (Fig. 1 . 2 2 ) . NEAL (1938) connects t h e p o t e n t i a l i n t e n s i t y of s h e e t e rosion G S

Gs

I

= K.

. i'"

- washed s o i l - g r a d i e n t of

(t.ha-' .min-') ( t . h a -1 )

the slope

(O)

(1.63)

57

i - rainfall intensity K - c o e f f i c i e n t of l o c a l c o n d i t i o n s

Fig. 1 . 2 1 . Biogeochemical c v c l e of n i t r q c e n a s a subsysteiii of the hydrologic cycle. The m i n r e s e r v e of n i t r o g e n is i n t h e atiiinsphere. From t h e chemical p o i n t of view, e s p e c i a l l y n i t r o g e n N: potassium K , calcium Ca, magnesium >\q a r e washed away, while sulphur S , c h l o r i n e C 1 and phosphorus P bond i n the organic and anorganic s o i l p a r t i c l e s . intercepted by t h e grassl.ands, meadows and

IJashed s o i l p a r t i c l e s nay be

p a s t u r e s , when eroded lands do n o t

d i r e c t l y a d j o i n the stream channel. Pl.ants i n such grassland zones a c c e p t n i t r o gen N qiiite e a s i l y , potassirmi K, calciiiiii Ca and phosphorus P a r e accepted only p a r t i a l l y . Sulphur S , natriuni Na and the r e s t of potissiuni K as well as of calcium Ca and phosphorus P a r e c a r r i e d away by the s u r f a c e r u n o f f . The ener,qy of t h e overland flow i n c r e a s e s w i t h i t s depth and v e l o c i t y . This f l o w is a c c e l e r a t e d and i t s dischar,ee g r w s with t h e l e n g t h of course. The

q u a l i t a t i v e change of the s h e e t erosion i n t o the pre-channel e r o s i o n depends

58 e s p e c i a l l y on the combination of the s o i l s u r f a c e c h a r a c t e r i s t i c s , r a i n f s l l int e n s i t y , gradient of t h e s l o p e and i t s length. The f o l l m i n g formula ca3 be derived f o r the c r i t i c a l length of the s l o p e , i . e . t h e length where the less dangerous s h e e t e r o s i o n changes due t o the concentrated flow and evoked forces i n t o pre-channel erosion: L = a L

a

f (i,r,t)

- critical -

i

.

length of the s l o p e

g r a d i e n t of the slope

(1.64)

(m)

(m)

(XI

c o e f f i c i e n t of s o i l c h a r a c t e r i s t i c s (0.5-4,5 2.3 - meadows)

: 1 - l e v e l l e d f i e l d s , 1.7-

r - r a i n f a l l and climate f a c t o r t - time f a c t o r , depending on the d u r a t i o n of r a i n f a l l s of high i n t e n s i t y

Fj.g. 1.22. Flow chart diagram of the e r o s i o n process. R a i n f a l l and runoff, the output o f t h e runoff system, a r e inputs of t h e erosion system. Output is: the sediment flow, s e t t l e d sediments and the water q u a l i t y .

S o l i d s o i l p a r t i c l e s e n t e r t h e movement of the concentrated overland flow a t the moment when its speed achieves the value of the speed l i m i t . This value depends on t h e weight, s i z e and shape of the r e l e v a n t p a r t i c l e s , which can be expressed by a simple formula vC = s . v v

-

speed limit of sediment motion

s

-

c o e f f i c i e n t of shape

d

-

size characteristics

C

(m.s-’)

(m. s-l>

(Tab. 1.20)

(1.65)

59 TABLE 1.20 Material

Grain size

Speed limit

(m>

(m.s-l>

Sand

Material

Grain size

Speed limit

(m>

(m.s-l>

Coefficient of shape Grain parameter value ( s )

3

0.108

Cobble rounded

27

0.650

round perimeter

6

0.189

Cobble an60 g u l a r , sharp

0.975

elliptic 4.43 long semi-axis

20

0.325

Boulders

100

1.400

angular 3.45 longest edge

4.46

Values of speed l i m i t s vc and shape c o e f f i c i e n t s s . Levi (1948) s ta tes f o r nonhomogeneous sedimen ts (1.66)

dm3x’ dmin’

d

s

- maximum,

g

-

h

- depth of flow

minimum and medium s i z e of sediment p a r t i c l e s

g r a v i t a t i o n a l constant

(m)

(m.s-2) (m>

A decrease i n t h e flow r a t e below the speed l i m i t causes a sedimentation of the s o i l p a r t i c l e s . A s t a b l e sediment s i z e is characterized by a s t a b l e gradient of the stream channel slope, as can be proved on t h e b a s i s of Ch&y’s formula: c

I

I n ;vc =

c2 .

R . i b = s 2 . d

ib = % .

’

d -- cb

ib

- balanced

cb

-

R

- hydraulic

.d

(1.67)

R

slope g r a d i e n t (without erosion and sedimentation)

c o e f f i c i e n t of t h e balanced s lope radius

(m)

V d e n t i n i (1893) s t a t e d cb = 0,093 f o r the s l o p e of t h e river bed up t o 25% and

V

- volume, n - number of

cobbles

60

The balanced slope gradient for smaller grain sizes follows d i r e c t l y from

k & y ' s equation: V

(1.68)

The current velocity is not uniform throughout the cross section and leads t o the transport of particles of different s i z e : For practical reasons the beginning of the motion of a considerable quantity of suspended matter is impor tant i . e . the relevant c r i t i c a l discharge, whose occurrence is some 180 days per year under conditions of stable natural r i v e r beds. Integrated processes of physical, chemical and biological character during wind, i c e , water and gravity erosion, entrainment, transportation and deposition of sediments, forming the Earth's surface and enabling the circulation of biogeoelements, a r e greatly affected by human a c t i v i t i e s . The universal equation for predicting erosion rates can be expressed by the function Ge =

f

(1.69)

(XI, X2> X 3 , Xh, Xg, x6, X7, x 8 )

C,

-

X2 X3

- c l i m t i c factor ( r a i n f a l l and wind intensity, ice phenomena) - hydrologic factor (concentration of the surface runoff) - topographical factor (slope-length, steepness and exposure)

X

-

e X1

4 X5

erosion r a t e

(t.ha-1)

s o i l factor (structure, texture, resulting in s o i l erodibility)

- geological

factor ( s t a b i l i t y of the ground)

X6

-

X,

- management practices

X8

- anthropogenetic factor ( e f f e c t of

vegetative cover factor (depending a l s o on season) factor (crop managenlent, irrigation) land developmnt/disturbance and protec-

tion measures)

The analytic t r a c t a b i l i t y of

the function is complicated by the need to

express the space-time characteristics of relevant factors, e.g. the coincidence of the r a i n f a l l occurrence and of d i f f e r e n t characteris t i c s of canopy during relevant growth stages : harvesting, bed preparation and other management pract ices

.

Water Quality as a Product of its Circulation 1.7.2 Water i n nature is a multiconstituent compound whose substance is hydrogen dioxide 3 0 containing dissolved and dispersed gaseous , liquid and solid cations , anions and nonionic constituents of anorganic and organic origin, as

w e l l a s aquatic flora and fauna.

61

The unique chemical c h a r a c t e r i s t i c s of the hydrogen dioxide H20, c a p i l l a r i t y with o t h e r unique physical c h a r a c t e r i s t i c s , a r e a consequence of the e x c e n t r i c position of oxygen with regard t o the c e n t r o i d of the water molecule. The very high d i e l e c t r i c constant of water permits i t to decompose molecules of s o l u b l e compounds i n t o ions and d i s s o l v e complicated m t t e r , a l s o forming s o i l s and rocks.

Fig. 1.23. Water and a i r a s b a s i c media of t h e g e e and b i o l o g i c a l processes a s w e l l a s of the matter and energy t r a n s f e r between continent and oceans. Water q u a l i t y c o n s i s t s of d i f f e r e n t p r o p e r t i e s , which a r e important when deciding about i t s p o s s i b l e u t i l i z a t i o n . These p r o p e r t i e s include temperature and colour, t a s t e and odour, caused by the presence o r absence of chemical substances and expressed by t h e a l k a l i n i t y , a c i d i t y , hydrogen-ion concentration,

62 content of carbonates (hardness), oxygen demand, sodium adsorption r a t i o , a s well as by the presence of different ionic and nonionic constituents incl. microorganisms etc. Various physical, chemical and biological characteris t i c s of water a r e formed by its contact with the environment during i t s circulation. Water quality changes most during i t s penetration through the s o i l and rock environment, but a l s o during i t s contact w i t h the atmosphere, vegetation, s o i l and rock during surface runoff and r a i n f a l l , further by mixing with water from deeper s t r a t a and by mixing and reacting with matter entering the system of atmosphere, hydro-, pedo- and lithosphere i n the course of h w n a c t i v i t i e s (Fig. 1.23). The complex of processes which create the characteristics, constituents and properties of water i s called mineralization. The course of these processes depends a l s o on the energy input, i . e . on the temperature, pressure and mechanical energy which crush the reacting particles, and on the concentration of acting components which come into mutual contact. Pores, cracks and cavities a c t as natural regulators of water quality: the r a t e of relevant processes a l s o depends on the s i z e of the acting surface, and on hydraulic parameters, especially on t h e flow r a t e , deciding about the duration of the contact of relevant constituents. Soil also functions as a natural f i l t e r , catching a subs t a n t i a l part of polluting natter and disposing i t by subsequent biochemical processes (Tab. 1.21). TABLE 1.21

Mineralization

cha rac teris t i c s

Me teogenic

Mineralization i n the atmosphere

Po tamogenic (f luviogenic)

Mineralization i n streams and r i v e r s , dependent on the s i z e , shape and geology of the r i v e r bed and on the velocity of the f l m a s w e l l a s on water temperature.

Limogenic

Mineralization i n lakes and other standing waters.

L i tomorphic

Mineralization i n groundwater, dependent on the petrographic and chemical characteris t i c s and on the influence of the underground atmosphere on the i n f i l t r a t e d water and groundwater

.

Ba thymrphic

Mineralization in deep aquifers determined especially by temperature, pressure, mgration, conservation and diaqenesis of the groundwater i n a way that i s composition closely depends on the depth.

Categorization of the mineralization processes which determine water quality, in undisturbed natural conditions.

63 The following physical and chemical processes take p a r t i n the formation of n a t u r a l water q u a l i t y : (a)

t r a n s f e r and d i f f u s i o n of oxygen and o t h e r gases,

(b)

d e s t r u c t i o n and crushing of matter and i t s d i f f u s i o n i n water, d i s s o l v i n g s o l u b l e and semi-soluble components of s o i l , rock and a i r ,

(c) (d) phere,

leachinn of mineral and organic p a r t i c l e s from the soil, rock and atmosmixing, d i l u t i n g and chemical r e a c t i n g of waters of d i f f e r e n t q u a l i t i e s ,

(e) (f )

(n)

s e p a r a t i o n of non-soluble p r e c i p i t a t e s and sedimentation, adsorption and desorption of soliited compounds on atmospheric, s o i l and

rock p a r t i c l e s and exchange of i o n s , r a d i o a c t i v e decay of elements.

(h)

The i n t e n s i t y of the physical processes of dissolving and ion exchange, and a l s o the chemical processes, e s p e c i a l l y those of d i s s o c i a t i o n and hydrolysis, depends on t h e s a t u r a t i o n of t h e s o l u t i o n by the mineral components. The s a t u r a t i o n index (1.70)

[A]

[B]

S

-

concentration of ions of the nonsoluble matter

-

constant

This s a t u r a t i o n index i n d i c a t e s the d i r e c t i o n of the r e a c t i o n . I the balanced state,

Is < 1 d i s s o l v i n g ,

S

= 1 mrks

I s > 1 separation of t h e insoluble

component. The r a t e of r e l e v a n t physical and chemical processes is proportional t o the concentration g r a d i e n t . This can be expressed by the equation (1.71) dc

-

r a t e of t h e adsorption and desorption processes (mg.1 -1 ,s-l )

k

-

c o e f f i c i e n t of the

C

- concentration of the d i s s o l v i n g component (mg. 1-I)

cb

- balanced

t

-

concentration

time

Integration offers

co

-

active surface

i n i t i a l concentration

(s-l)

(w.1-3 (S)

64 and consequently

c - Cb - e -kt co- c b

--

(1.72)

With regard t o the r e l a t i v e l y small value s of the balanced concentrations, cb can be neglected

(1.73) These equations prove t h a t the r a t e of d i s s o l v i n g rock and s o i l p a r t i c l e s , and also the r a t e of d i s s o l v i n g deposition of insoluble compounds i n t h e rock environment of pores and cracks, i s governed by exponential r e l a t i o n s . 'Ihe speed of these processes i s higher i n an environment where a c t u a l concentrations d i f f e r r e m r k a b l y from the balanced concentration than i n an environment where t h i s d i f f e r e n c e is smll (Tab. 1 . 2 2 ) . 'Ihe balance of running d i s s o l v i n g and ion exchanging processes i n the system

soil/rocklnrater depends on the s o l u b i l i t y of the rock, on the chemical car'posit i o n of the water and i t s temperature, on the a c t i n g s u r f a c e , depending on the p o r o s i t y and s i z e of t h e rock p a r t i c l e s . The dependence between the s o l u b i l i t y and t h e s i z e of the s o i l p a r t i c l e s can be expressed a s

(1.74) ck

-

s o l u b i l i t y of s m l l c r y s t a l s

cr

-

s o l u b i l i t y of p a r t i c l e s w i t h the s i z e r

( s i z e 10-%,I

a , b- cons tan ts Diffusion r a t e a t the constant value of the concentration g r a d i e n t (1.75) dn dc

=

change of the number of mols passing t h r o u h a r e a f

--

concentration g r a d i e n t

D

- diffusion

f

-

coefficient

area

I n most c a s e s , the concentration gradient depends on time, which describes a p a r t i a l d i f f e r e n t i a l equation, whose s o l u t i o n leads to the r e l a t i o n

65

(1.76) cs - concentration of the saturated solution

- integration variable.

y

TABLE 1.22 a) 1)issolving of gases

b)

Dissolving of minerals

02"2 ,C02,H2S,HC1,m3,Ar Kr,Xe,Ne,Hc

,Fe(0H)3 ,NaC1,FeC03, MnC03 a td. %GO3

Mixing of waters:

ql.

Cl

+ q2.c2 = 100

.

qS

Chemical reactions: A) Oxygen 0: O2 + 4 H+

-

A

H2°2

d

H7°2

B) Calcium Ca a2+ + C02 + H 2 0 Z C a2++2 HC0;

2 H20 O2

+

H20

2H

Ca2+ +

~032-

D) Manganese Pln

Fez+

+ H20

Fe (OH)'

+ H+

k2+ + H20

Fe(0H)'

+

H20

Fe(OH)2

+ H+

&(OH)++

Fe(OH)2

+

H20

Fe(OH);

+ Ht

Mn(OH)z

Fe3+

+ H20

Fe(0H);

FeC0H)2+

+ H20

Fe(OH)3 + H20 G) Sulphur S: H2S

30 + €$SO3

23 H20 + S

+

H+

F~(oH)~+ + H+

H20

d

A

d

CaC03

A

2 H'

+

C) Iron Fe

Fe(OH)'++

-

-

MIn(0H)'

+

H+

H20

Mn(OH>2

+

H+

+H20

MII(OH)T

+

H+

d

E) Alluminium Al: Al(OH)g+ OH-

Fe(OH)3

+ H+

A1(OH)3+

Fe(0H);

+ H+

Al(0H)Z

%O

d

A102

+

A1coH);

2 H20 +

H+

A10; + 2 %O

F) Silicon Si: S+2Hf SO-:

2

+

4 'H

s-

H2S03 + 4 H+

caA12si208 + H ~ O+ 2 H+

A

A12Si205(OH)4

H) h o n i a NH4: No; + H20 NO3 + 10 'H NOS f 2 'H

+

L

-

Ca2+

2 OH- + NO;

L

NK4 + 3 H20

L

HN02 + H20

Selected characteristic physical and chemical processes which form water (especially groundwater) quality.

66

Chemical reactions mostly

take place when water of different origin is

mixed. Where these reactions are missing, the resulting water composition is

q1

. c1

+ q2

. c2 =

100

.

(1.77)

cS

- quantities of mixed waters c1 , c2 - concentration of non-reacting cS - resulting concentration

q l , q2

(XI components i n mixed waters

(g. 1-I)

(g. 1 - 5

Solid p a r t i c l e s suspended i n water a r e affected by chemical and physical, especially hydraulic forces. Under prevailing hydraulic forces, the intensity of the interception of s o l i d p a r t i c l e s i n rock formations is low: their function m y even wash out rock p a r t i c l e s , i . e . cause suffusion. Under the prevailing influence of chemical forces there occurs a gradual cracks, resulting i n a decreasing coefficient of hydrau-

clogging of pores and l i c conductivity

.

The course of the groimdwater flow depends, therefore, on the coincidental physical and chemical reactions. Slightly polar substances a r e intercepted quite e a s i l y and i n the proximity of the

i n f i l t r a t i o n point. More polar sub-

stances a r e d i f f i c u l t to intercept. The interception of basic, alkaline components depends to a remarkable extent on t h e i r chemical composition. Iwasaki (1974) states t h a t the decrease i n the concentration percentage is proportional to the actual concentration

(1.78)

E‘ =

( A + K . s ) . c

c

-

concentration percentage

(%I

L

the thickness of the layer

Cm>

A,K

-

s

-

constants the volume of suspended particles intercepted by the u n i t volume of the layer

The volume of intercepted p a r t i c l e s

;

- - - -vf

.

+

(1.79)

vf - apparent velocity of the groundwater flow (m per day) The above-mentioned physical and chemical processes usually determine the quality of

MtUrd

waters i n the underground:

on the Earth’s surface and above

it. These processes are often accompanied by biological, o r bacteriological processes. These usually depend not only on the thermal energy input or output, but a l s o on luminous energy.

67 F r m the biological point of view, the complex of local physical, chemical and other conditions i s named biotope. The development of a biocoenosis, a comnunity of organism, depends on t h i s biotope. Each type of biotope contains not only c h a r a c t e r i s t i c organisms, but a l s o organisms which a r e usual i n other biotopes and which have been brought i n by chance. The resulting water quality can be c l a s s i f i e d (a)

formally

(b)

genetically i n accordance with the p o s s i b i l i t i e s of i t s u t i l i z a t i o n ,

(c)

(d) i n accordance with i t s influence on biological factors. Systematic categorization, enabling an e x p l i c i t genetic c l a s s i f i c a t i o n on the basis of formal Thysical and chemical factors, has not y e t been developed. Different c l a s s i f i c a t i o n s a r e , therefore, used for the c l a s s i f i c a t i o n of surface waters and groundwa t e r s

.

Groundwater can, i n accordance with its chemical composition, be c l a s s i f i e d as

(a) plain - containing l e s s than 1 g of dissolved substances i n 1 l i t e r , (b) brackish - containing 1 t o 30 g of dissolved substances i n 1 l i t e r , (c) brine - containing more than 30 g of dissolved substances i n 1 l i t e r of water . Waters which contain m r e than 1 g of carbon dioxide CO2 i n 1 l i t e r a r e denoted as acidic. Natural mineral waters contain e i t h e r more than 1 g of dissolved substances o r of carbon dioxide. Waters whose healing properties have been s c i e n t i f i c a l l y proved m y be described as medicinal, o r curative. The c l a s s i f i cation and terminology of mineral waters can be derived from p a r t i a l c l a s s i f i cation according t o the content of dissolved gases, quantity of dissolved s o l i d s , main ion components, biologically and pharmaceutically important components, chemical reaction, radioactivity , osmotic pressure and temperature. T h e m 1 waters whose temperature generally exceeds 25OC can be c l a s s i f i e d as

- hypo t h e m 1

25-35OC

-

35-42OC

-

isotherm1 hyper t h e m 1

> 42OC. The c l a s s i f i c a t i o n of groundwaters on the basis of t h e i r chemical composition

is governed e i t h e r by the prevailing ions o r by the prevailing ion combinations. J e t e l (1975) connects both these principles i n the following way and differentiates: - classes S, C , N, C 1

-

-

accordinE t o the representative anion SO4, H a 3 , N, C1,

groups according t o the representative cation Na, K , M g , Ca.

Contents ( r ) of other ions a re t o be added t o the similar main ions: Mn" Fe2+ to Ca2+, NO t o C l - and alkalines t o Na', cO$- to HW;. 3

and

68

-

s p e c i e s according t o combinations of t h e m i n i o n s , m r k e d by Rown f i g u r e s

(Tab. 1.23). The symbol of groundwater q u a l i t y forms marks of the main a n i o n s , c a t i o n s , s p e c i e s and t h e value of t h e t o t a l m i n e r a l i z a t i o n , e . g . CINa - 0,014 g.1-'. i1

TABLE 1 . 2 3 Index 1

Hypothetical combinations of ions NaCl

Na2S04

Characteristic r e l a tionship

NaHW3

rHCQ3>

Mg(HC03)2

rNA

>

r(Ca+Mp) r(C1+S04)

(HCO3)2

I1

NaCl Na2s:4 MWq

Mg (Hm3 12 Ca(HC03)2

rHC03

<

r(Cl+S04) NaC1

r(Ca+Mg)

>

rNa

>

<

r(HC03+S04) i.e. rC1

Na2S04 M@04

IIIa

CaS04

Ca(HC03)2

MgS04

Mg(HC0312

NaCl

MS12

Ca(HC03)2 NaCl MgC12

>

<

Ca(HC03)2

NaCl

MSl IV

>

MgS04

CaS04 IIIb

<

rCa r(HC03+S04) r(CaiMg) i.e. r(Na+Mg) rC1 rNa

rCa

CaC12

CaS04

NaCl

Na2S04

rC1

> >

r(HC03+S04) i.e. r(Na+Mg)

MgS04 &SO4

H2S04 NaC 1 MgCl

rHm3

= 0

MgS04 Caso4

H2S04 NaCl

caso4

MgC12 CaCl2 Groundwater c a t e g o r i z a t i o n depending on ion c m b i n a tions according to Alekin (1970). I V . s p e c i e s c a t e g o r i z e d according t o F l o r e a (1970).

69 The q m l j t y o f s u r f a c e waters depends t o a g r e a t e x t e n t on h y d r o l o g i c a l , meteorological and antropogenetic f a c t o r s and changes considerably w i t h time. The chemical composition of these water i s n o t the p r e v a i l i n g agent of t h e i r quality . Their m i n e r a l i z a t i o n i s remarkably lower than t h a t of groundwaters. The q u a l i t y of siirface w a t e r , t h e r e f o r e , is t o be defined on the b a s i s of f u r t h e r c h a r a c t e r i s t i c i n d i c a t o r s : oxypen regime, microbiological and o t h e r i n d i c a t o r s (Tab. 1.24) and a l s o w i t h regard t o i t s p o s s i b l e u t i l i z a t i o n . Oxygen demnd i s the a b i l i t y of substances t o u t i l i z e t h e d i s s o l v e d oxygen f o r t h e i r s t a b i l i z a t i o n . Chemical oxygen denland (COD) i s a measure (mg 02, 1-l) of the m a t e r i a l s p r e s e n t i n water which may be r e a d i l y oxidized, i n order t o a s c e r t a i n the amount of o r g a n i c and reducing m a t e r i a l . Biochemical oxygen demand (BOD) i s t h e amount of oxygen used by a q u a t i c microorganisms i n t h e i r metabolic processes. The e v a l u a t i o n of t h e

ROD r a t i o o f f e r s the b a s i c informa-

t i o n concerning the c o n t e n t of b i o l o g i c a l l y degradable and r e s i s t a n t constituen ts . The amount o f d i s s o l v e d oxygen (mg.1-')

depends on t h e water q u a l i t y . The

d i f f e r e n c e between the maximum p o s s i b l e concentration of oxygen (depending on temperature - Tab. 1.24) and the a c t u a l c o n c e n t r a t i o n is termed oxygen d e f i c i t . Their r a t i o is marked a s s a t u r a t i o n r a t i o . Very important i n d i c a t o r s of t h e b a s i c chemical compositipn include the value o f t o t a l d i s s o l v e d s o l i d s TDS (mg.1-')

and t h e value of suspended r a t t e r :

The c o n c e n t r a t i o n of ions i s p r e s e n t l y followed i n m u l t i p l e s of the content of

rmtter i n a system, whose number of molecules is equal to the number of atoms i n 12.10%g Na+

of carbon i s o t o p e I2C a t 1 l i t e r ( m l . l - ' ) .

, Ma2+ are

, SO:-,

The ions C1-

followed i n p a r t i c u l a r .

C o n s t i t u e n t s which may s i g n i f i c a n t l y a f f e c t the a p p l i c a t i o n of water f o r b e n e f i c i a l purposes include c a t i o n s , namely sodium Na+, potassium K+ and Mn+

,

calcium Ca+ and magnesium Mp'

a m o n i a NH4; hydroxide OH

c h l o r i d e C1-

, are

, and

, further

,

i r o n Fe+

,

a n i o n s , namely n i t r a t e NO; and

a l s o bicarbonates HCO-

3

, carbonate

CO- and

3

g e n e r a l l y considered i n t h e l i g h t of t h e i r i n f l u e n c e on a l -

k a l i n i t y and hardness. Nonionic c o n s t i t u e n t s include e s p e c i a l l y d e t e r g e n t s , o i l y substances, phenols, cyanides and s i l i c a ( s i l i c o n dioxide Si02). The sum of t h e c a l c i i m and magnesium, expressed as a n e q u i v a l e n t amount of calcium carbonate, was i n the p a s t followed a s water hardness and is p r e s e n t l y replaced by a s e p a r a t e following up of both these c a t i o n s . An important i n t e g r a t e d property of water i s t h e hydrogen-ion concentration pH, the n e g a t i v e logarithm t o t h e b a s e 10 of t h e hydrogen-ion concentration. A balance between d i s s o c i a t e d hydrogen and hydroxyl ions denotes a pH value of

7.0, b u t t h i s value has no special s i p i f i c a n c e as a n expression of a l k a l i n i t y and a c i d i t y .

70 TABLE 1.24

Class

Ia

Characteris t i c s

very clean

a ) Indicators of the oxygen repime -1 Dissolved oxygen mg.1 -1 mg. 1 mD5 Oxidizability by mg.1 permangana t e Saprobi ty

Ib

I1 clean s l i g h t l y polluted

>o

>7 (2 <5

(5 (10

oligo-

p-meso

>

5
111

IV

intensively polluted

deteriorated

>3 (15 25

<3 >15 >25

<

d- meso

poly -

meso b) Chemical indicators Dissolved matter Suspended mtter

-1 mg .1 -1 mg. 1

<300 20

<

<500 < 20

(800 30

<

(1200 < 50

>1200 50

>

c ) Special indicators

>6.5 (8.5

PH 1) Tempera ture

< 22

6.5-8.5

6.0-8.5

(23

<24

5.5-9.0 06

(5.5 >9.0 >26

d) Indicators of the microbiological pollution Coli index

pc.1

> 106

Categorization of surface waters according t o the basic indicators of water pollution. 1) i n mild continental climate. A pH value of l e s s than 7 . 0 denotes a n excess of hydrogen ions. Such water is called a c i d , when the value pH is below 4.5. Acidity is caused especially by f r e e mineral and carbonic a c i d s . A pH value greater than 7.0 indicates an excess of hydrogen ions, the alkal i n i t y , i . e . a b i l i t y of t h i s water t o n e u t r a l i z e a c i d s . Alkalinity i s caused especially by hydroxide, carbonate and bicarbonate. Sensoric properties such as temperature, colour, t u r b i d i t y , odour and t a s t e a r e very important indicators of water q u a l i t y , influencing i t s u t i l i z a t i o n for drinking purposes. They depend on the chemical and biological ccinposi tion of water .

A simple indicator of water q u a l i t y is the e l e c t r i c a l conductivity, which depends on the concentration of s a l t s and r e f e r s t o the conductivity of a one centimeter cube of water a t 25OC.

On the b a s i s of a s e t of graduated i n d i c a t o r s , s u r f a c e waters can be divided

i n t o several c l a s s e s (Tab. 1.24). For a b e t t e r appreciation several less f a v o u r able values should be c o l l e c t e d uniformly throughout the year. The c l a s s i f i c a tion i t s p l f has t o be c a r r i e d o u t using a r i t h m e t i c means a f t e r the exclusion of values influenced by heavy r a i n f a l l s . On the b a s i s of the u t i l i z a t i o n of water f o r drinking purposes three c l a s s e s can be distinguished ( a ) water r e q u i r i n g mechanical treatment and d i s i n f e c t i o n only, o r not requiring treatment a t a l l , (b) water r e q u i r i n g chemical treatment, ( c ) water not s u i t a b l e enough o r u n s u i t a b l e f o r municipal water supply (high content of nitrogen N , i r o n Fe o r mnganese Mn, high mineralization, high content of calcium Ca and magnesium Mg, f l u o r i n e F , a s well a s chemically, r a d i o l o g i c a l l y , b i o l o g i c a l l y o r b a c t e r i o l o g i c a l l y highly p o l l u t e d waters.

1.8

HYDROLOGIC CYCLE AS REGUIATOR OF BIOLOCICAL PROCESSES

The biosphere i s a n open system of anorganic and organic, l i v i n g and withered matter on the Earth, transforming s o l a r energy by means of b i o l o g i c a l processes. Complicated water s o l u t i o n s of compounds of biogenetic elements formed by

l i v i n g environment before the gradual development of l i f e (Fig. 1.24). The presence of b i o e l m e n t s i n water a s w e l l as the presence of water i n nutriments and organic matter has a b a s i c importance f o r metabolic processes and the prowth of l i v i n r m t t e r (Tab. 1.25). Living matter, o r biomass, c o n s i s t s of the three main components: p r o t e i n s , f a t s and s a c h a r i d s . During the decay of organisms, absorption and d i s i n t e g r a t i o n of nutriments, water is separated from a l l the mentioned canponents (Fig. 1.24). The c i r c u l a t i o n of matter can be followed a s chains of n u t r i t i o n i n connection with the energy t r a n s f e r . Organisms can be c l a s s i f i e d according t o t h e i r relat i o n t o t h i s c i r c u l a t i o n a s producers, consumers and d e s t r u c t o r s . Organisms which produce organic matter by consuming anorganic compounds (microorganisms, f l o r a e t c . ) a r e termed a s producers. Organisms which a r e not able t o perform t h i s function and consune organic matter, formed by producers and o t h e r consumers, a r e termed a s consumers (animals e t c . ) . Destructors a r e organisms which decompose organic matter, thus producing anorganic canponents (microorganisms e t c . ) (Tab. 1.26). I n ecosystems, subsystems of the biosphere, these b i o t i c c m u n i t i e s a r e interconnected with the b i o t i c and a b i o t i c environment, thus forming closed and independently functioning systems, whose b i o t i c s t r u c t u r e , cycle of nutriments and energy f l w can be e x a c t l y determined (Fig. 1.25). The energy i n ecosystems b a s i c a l l y has three forms:

-

k i n e t i c energy

- whose

manifestation is e x t e r n a l motion,

72

-

p o t e n t i a l energy

-

-

i n t e r n a l energy

- mnifestated

accimulating i n r e l a t i o n t o the environment, by i n t e r n a l movement and i n t e r n a l r e l a t i o n s .

TABLE 1 . 2 5 Function

Description

Solution

Water d i s s o l v e s p a r t i a l l y o r f u l l y the p r e v a i l i n g p a r t of

dissolving

anorganic and organic compounds , forming foodstuff and nut-

agent

riments.

Chemical

Water f i s s u r e molecules, whose motion enables the approach

activator

and mutual r e a c t i o n of molecules of d i f f e r e n t compounds.

Heat

The high s p e c i f i c h e a t of water helps t o maintain a s t a b l e

regula t o r

temperature of organisms , without any excessive f l u c t u a t i o n . Its optimum value i s kept by evaporation of water, which

r e q u i r e s much energy because of the high l a t e n t h e a t of vaporization. Regulator

The propagation of pressure i n water is uniform i n a l l

of

d i r e c t i o n s , enabling the c e l l u l a r pressure to be maintained

pressure

and regulated.

Distribution

Water d i s t r i b u t e s nutriments t o and takes away wastes from

agent

d i f f e r e n t p a r t s of the l i v i n g organisms. I t a l s o d i s t r i b u t e s t h e m 1 energy, transporting i t from the place of i t s occurrence (muscles, l i v e r ) t o cooler p a r t s ( s k i n ) . ~

~~

Economizing

The u n i t mass of these water organisms is the same a s t h a t

agent f o r

of water, thus removing the e f f e c t of g r a v i t y and econanizing

water organisms

t h e i r energy requirements.

Functions of water i n the b i m s s . The transformation of energy during i t s flow through the ecosystem takes place i n accordance with physical laws, i t s manifestation is the motion and change of temperature. Apart f r a n the law of conservation of energy, the law of degradation of energy a l s o makes i t s e l f f e l t : during any process p a r t of the energy changes i n t o h e a t . According t o Darwin-Lotke's r u l e , during a quick change of energy, h e a t losses form one h a l f of t h e energy t o t a l . Due t o these enerRy l o s s e s , any process i n ecosystems i s one-way. Heat l o s s e s a r e transferred t o the environment.

73

'rote I n s

&achharoids

rats

-GLYCEROL

CO,

H*0

Fig. 1.24. Block diagram representing t h e decay of the b a s i c components of the biomass. Processes: AE - a e r o b i c , AN - anaerobic, HY - hydratation, HU humif i c a t i o n , N I - n i t r i f i c a t i o n , DE - decarboxylation, dezamination, hydrolysis.

-

The ecosystem is a ccrmnunity, including a l l organisms of a c e r t a i n space, and a b i o t i c elements, a c t i n g i n the c l i m a t i c regime, whose r e l a t i o n with the e n v i r o r ment is s t a b l e and determined, by the input and output of energy and matter. The formation of regional ecosystems depends on topographical, s o i l and c l i matological conditions with the p r e v a i l i n g influence of s o l a r r a d i a t i o n (temperature) and r a i n f a l l (Tab. 1.27). I n n a t u r a l ecosystems of € o r e s t s , steppes, d e s e r t s , water formations e t c . the input of matter is not s i g n i f i c a n t l y a f f e c t e d by hmmn a c t i v i t i e s ( p o l l u t i o n ) and s o l a r r a d i a t i o n is the s o l e source of energy. I n the framework of these regional ecosystems, depending on the nlacroclimte, l o c a l ecosystems e x i s t , influenced e s p e c i a l l y by the l o c a l topographic, s o i l and moisture conditions and by t h e conditions of t h e meso- and microclimate. With regard t o t h e wetness of t h e i r h a b i t a t s , p l a n t s can be c l a s s i f i e d i n four groups (Tab. 1.28).

74 TABLE 1.26

Organic groups (species)

Nutriment substance

Production

Process

Simplified formula

Producers

anorganic

oxygen

Photo-

6 C02 + 6 H20 + 1612 W =

(green plants,

compounds of biogeo-

biomass

synthesis

'gH12'6

sulphur bacteria)

e l ements

Chemosynthesis

6 C02 + 6 H S + energy = 2 C6H1206 + 6 S

Biological uptake

265 CH20 + 16 NH3+ PO4+ 146,5 O2 -+ energy =

+

2'

c106H180°45Nl.6' + 159 CO, + 199 H,O L

L

Consumers

organic

waste or-

decompo-

(herbivore, carnivore

matter: proteins,

ganic

s i t i o n of

C6H1206 + 6 O2 =

matter

sach-

6 c02

omnivore)

sachharoids fat

C02

haroids

+

6 H20 + 1 6 1 , l kJ

H20

Detrivore

Waste

cop

(fungi, bacteria)

organic matter

MI3, SO4 PO3, s a l t s

H20

decomposition

Ca t.egorization of n u t r i e n t r e l a t i o n s h i p s i n t e r r e s t r i a l o r a q u a t i c ecosystem. Nutrients c o n t i n u a l l y c i r c l e w i t h i n t h e boundaries of t h e ecosystem. Fluxes across the ecosystem's boundaries l i n k it with the environment, i . e . n u t r i e n t , s o i l and atmospheric compartment. Four zones of p l a n t c o r n u n i t i e s can be distinguished along the water courses and r e s e r v o i r s a s a r e s u l t of the impact of water l e v e l f l u c t u a t i o n (Fig. 1.26, Tab. 1.29). Living processes and changes i n ecosystems a r e mnaged by t h e t r a n s f e r of m t t e r , e s p e c i a l l y by means of water and a i r , and energy. Under the influence of human a c t i v i t i e s s t a b l e n a t u r a l ecosystems change i n t o ( o f t e n unstable) anthropogene t i c ecosys tern ( a ) a g r i c u l t u r a l e c o s y s t e m , where t h e dominant source of energy is s o l a r r a d i a t i o n and t h e climate determines the type of c u l t i v a t e d a g r i c u l t u r a l p l a n t s , b u t the flow of matter and energy is s i g n i f i c a n t l y influenced hy hunnn a c t i v i t i e s , (b)

i n d u s t r i a l e c o s y s t e m , where i n a d d i t i o n t o the supplemented input of

matter , the energy i n p u t is considerably supplemented by mn-made energy,

75

Fig. 1.25. Circulation of water and nutriments i n ecosystems: the transfer of mtter including water, proteins, sachharoids, f a t etc. is represented by thick black arrows, energy input and output by thin arrows. The impact of pollution (dotted arrow) changes the input of nutriments , improving l i v i n g conditions f o r detrivores , thus changing the ecological succession t o the disadvantage of c a r nivores f i r s t . J - energy TABLE 1.27 Minimum MaXinum

-

wtirmnn

tundra

-

Optimum

Maximum

steppe mixed and coniferous forest salty marshes

desert trop ica1 monsoon forest tropical jungle

The dependence of the basic natural ecosystem on temperature and r a i n f a l l .

76 TABLE 1.28

Category

Character is tics

Selected species

Hydrophytes

grow i n water swamps and bogs

water p l a n t s , phytoplankton, pondweed, r i c e , c a t t a i l

Hygrophytes

need moisture, not r e s i s t a n t a g a i n s t drought

f e r n s , moss

Nesophy tes

medium water requirements survive both s h o r t periods of wetness and drought

g r a s s e s , wood

Xerophytes

low water requirements drought-resistant

c a c t i , haloxylon

~~~

~~~

Categorization of p l a n t s with regard t o the r e l a t i v e wetness of t h e i r h a b i t a t s .

Fig. 1.26. The development of t h e f l o r a i n the s u b l i t o r a l ( l ) , l i t o r a l (lower 2 , upper - 3 ) and a s u p r a l i t o r a l ( 4 ) zone along a stream o r a r e s e r v o i r shore depends on t h e frequency of flooding and on the groundwater t a b l e . S o f t species occur e s p e c i a l l y i n the l i t o r a l zone, hardwood species i n the s u p r a l i t o r a l zone. (c) degradated ecosystems, where the a d d i t i o n a l input of mtter (water, a i r and/or s o i l p o l l u t i o n ) changes the input of energy and r e s u l t s i n the d i s i n t e -

g r a t i o n of s t a b l e n a t u r a l ecosystems.

77 TABLE 1.29

Zone

Characteris t i c s or limitation

wood

Characteristic o t h e r species

Sltpra-

flood only

Hard: oak, maple,

li t o r a l

exceptionally

elm, ash-tree

grasses,

water t a b l e Upperlitoral

occasionally flooded

S o f t : willow, poplar, a l d e r

bramble, n e t t l e , meadows w e e t , rush, w i 11ow-herb

S o f t : willow, a l d e r , hedge,

brooklime, bulrush, monkey flower, water c e l e r y ,

water t a b l e 0150d Lower

frequent water

lit o r a l

table fluctuation

Sub-

water t a b l e C)360d pemnently

litoral

flooded

water mint, water forgetme-not, reed, reed-grass no trees

bog-pond weed, bulbous rush, f l o a t i n g

clubrush,

w a t e r l i l l y , water crow f o o t , strapweed C l a s s i f i c a t i o n of shore zones according t o the frequency of t h e i r flooding and c h a r a c t e r i s t i c r e p r e s e n t a t i v e s of r e l e v a n t p l a n t ecosystems! I n t e r r e l a t i o n s h i p of Aquatic Ecosystems and Water Q u a l i t y 1.8.1 An a q u a t i c ecosystem, i . e . a system of organic communities i n a c e r t a i n water f o m t i o n , where t h i s c a m u n i t y l i v e s i n a s t a b l e r e l a t i o n with i t s abiot i c environment, r e p r e s e n t s a n example of a closed chain of n u t r i t i o n . I n t h i s enviornment, L i e b i g ' s law of minimum is of p a r t i c u l a r s i m i f i c a n c e : The missing enerEy o r bioelement decides on the course of the production process. I t is impossible t o prove the presence of such l i m i t i n g bioelements (usually phosphorus P, potassium K , nitrogen N e t c . ) i n water, because i t is changed i n t o organic matter imnediately a f t e r i t s e n t r y i n t o the system. The production process i s , i n a d d i t i o n t o t h i s , a l s o governed by the presence of matter s t i m u l a t i n g the growth, primarily of vitamins: tiamin, b i o t i n , cobaltamine etc. The consequence of a high content of nutriments and s t i m u l a t i n g niatter i n water is eutrophication, manifestated by i t s b i o l o g i c a l overproduction. Uhhlmnn (1975) expresses the c i r c u l a t i o n of matter i n the a q u a t i c ecosystem by the d i f f e r e n t i a l equation. The change i n the concentration of biomass can be formulated a s follows:

dz x =2k21.P.Z

+ 2k24.B.Z

-

k02.Z

-

lk42.Z

-

2k32'F'Z

(1.80)

78 2

- zooplankton

P

- phytoplankton

B

-

bacteria

F

-

fishes

Ik - c o e f f i c i e n t of r a t e f o r r e a c t i o n of the 1.range *k

-

c o e f f i c i e n t of r a t e f o r t h e r e a c t i o n of the 2.range

The index on the r i g h t of the c o e f f i c i e n t s marks the r e c e i v e r ( 1 s t number) and the s u p p l i e r (2nd number).

HYTOPLANKTON

ZO0PL:NKTON

FISHES

1

I

$

ENERGY

BIOMASS

MATTER

Fig. 1.27. Couplings of t h e a q u a t i c ecosystem according to Ihlmann (1935): phytoplankton ( l ) , zooplankton (2), f i s h e s ( 3 ) , b a c t e r i a ( 4 ) . Index i j m r k s the t r a n s f e r of ratter o r energy from the p a r t j to the p a r t i of the ecosystem, 0 - the a b i o t i c environment. The biomass i n flowing waters is influenced by the inflow, a s can be expressed by t h e d i f f e r e n t i a l equation adxf = p . X + Q . X ' - ( i 1

- biomass ("L - d a i l y increment

X

ratio

+ i ) . X 2

(1.81)

79 - water inflow

Q

(1.d-')

X' - s p e c i f i c inflow of the biomass

( g . 11-l)

il - r a t i o of biomass outflow

w-5

i2 - r a t i o of biomass u t i l i z a t i o n by con-

(d-')

sumers and d e s t r u c t o r s

I n newly constructed r i v e r channels and a f t e r the flood

dx

>> 0.

(1.82)

After t h i s i n i t i a l phase, the value of t h e b i o m s s increment decreases t o the value of the b i o l o g i c a l balance, characterized by = -o

dt

.

(1.83)

R e water q u a l i t y with regard t o i t s b i o l o g i c a l p r o p e r t i e s can be c l a s s i f i e d i n terms of i t s saprobity o r t r o p h i c i t y . The saprobity is the biological s t a t e of water, determined on the b a s i s of the presence o r absence of biocoenosis, t h a t i s c h a r a c t e r i s t i c f o r a c e r t a i n degree of biochemical decay, i . e . i n relation to the degree of p o l l u t i o n (Tab. 1.30). The saprobity c h a r a c t e r i z e s the changing p r o p e r t i e s of the water environment during a c e r t a i n period, thus d i f f e r i n g from the physical and chemical indicat o r s , which c h a r a c t e r i z e the a c t u a l s t a t e only. For t h i s reason, an e x p l i c i t r e l a t i o n between the s a p r o b i t y and r e l e v a n t physical and chemical i n d i c a t o r s does n o t e x i s t , though the c l a s s i f i c a t i o n sys t e m of saprobity is closely i n t e r r e l a t e d with the b i o l o g i c a l oxygen demand (BOD) of water (Fig. 1.28). The t r o p h i c i t y is the a b i l i t y of water to nourish water organisms. Nauman (1932) c l a s s i f i e d the t r o p h i c i t y on the b a s i s of the s u r p l u s , average o r undersized values of the b a s i c physical and chemical preconditions of the development of d i f f e r e n t biocoenosis. Seven b a s i c trophical types of stagnant and flowing waters follow a s a consequence of combining these c r i t e r i a (Tab. 1.31).

Some changes and combinations a r e chemically impossible, such a s a l k a l i t r o p h i c i t y with s i d e r o t r o p h i c i t y , a c i d o t r o p h i c i t y and d y s t r o p h i c i t y , o r acidotrop h i c i t y with e u t r o p h i c i t y . A p r a c t i c a l c l a s s i f i c a t i o n is based on t h e mean annual values. The views on t h e i n t e r r e l a t i o n s h i p of the saprobity and the t r o p h i c i t y have not y e t been u n i f i e d . Kolkwitz (1935), SlAdeCek (1961) and o t h e r s state t h a t the eutrophization and s e l f - p u r i f i c a t i o n processes are only two d i r e c t i o n s of one n a t u r a l process, r e l a t i n g i n t h i s way the denee of saprobity with the degree of t r o p h i c i t y . The scale of t r o p h i c i t y i s then the r a t i o of the production of l i v i n g nlatter to r e s p i r a t i o n , l i b e r a t i n g the organic energy, bonded by l i v i n g matter.

80

Fig. 1.28. C i r c u l a r r e p r e s e n t a t i o n of water q u a l i t y by degree of s a p r o b i t y and r e l e v a n t s tructrire of a q u a t i c ecosystems according t o Sl5deCek (1972): Linmosaprobity: (x-xeno, 0-oligo, B-brtamezo, d-alphameso, p-polysaprobitv), Eusaprobity ( i - i s o , m-meta, h-hyper, u - u l t r a s a p r o b i t y ) , Transaprobity (a-anti , r-radio, k-kryptosaprobity). Detrivore marked black: R-bacteria. Consiunersherbi-, carni-and omnivore niarked d o t t e d : Z-zooplankton, C - c i l i a t a , F-zooflag e l l a t a . Producers- Ereen p l a n t s and a u t o t r o p h i c b a c t e r i a m r k e d white: Pphytoplankton, M-mixotrophic f l a g e l l a t a . O-no l i f e . Arrows show the d i r e c t i o r i of e u t r o p h i z a t i o n (1) and f u r t h e r p o l l u t i o n (Z), decay and s e l f - p u r i f i c a t i o n ( 3 ) . Dsahed segment r e p r e s e n t s the i n c r e a s e i n m a t e r i a l i n p u t and output (and a l s o the i n c r e a s e i n t h e b i o l o g i c a l oxygen demand).

TABLE 1.30 Process

Symbol Saprobi t y

o

ri

P

Degree of saprobity

Pollution (degree)

BOD5 Plankton (in

5

mg.1-'

m

m1-I)

Primary production -3 3 . -3 (w.m ( R . m (mg.m ) .d-]) .yeard1

$

3 abiotic

29

L Limosaprobi ty

2 3

no l i f e completed .rl u oxyda t i o n .:completed greduction 0

a bstarting 33 . . z o x y d a t i o n d io . c 0

.," reduction 4-1

x

xenosaproblty

without pollution very l i g h t

';Ib i o l o g i c a l

54 2 J

3

m u

0 7

0

1

0

0

1

100

1

50

a

0 , 2 zatrophicity ultra-

10

ol i p t r o p h i c i t y o

fi

5

1o5

medium

10

lo6

5 100 30 (20) (1500) (5001 300 500 150 ( 1500) ( 12000) (40OO) 1000 1500 300-

heavy

50

lo7

10000

12000

4000

3

100

30

oligosaprobity l i g h t mesosaprobity

medium

d mesosaprobity p

i

polysaprobity isosaporbity

(ciliatic)

me tasaprobity

(hydrogen sulfidic)

hypersaprobity (bacteriologic) ultrasaprobity (abiotic) T Transsaprobity

a

0

2,5

1000

o l i g o t r o p h i c i ty

,L3 -eu t r o p h i c i t y

,d

! 2 . u predominant

E Eusaprobity

3 Trophici ty

2

i

C R

K Katarobity

U

Chlorophyle

Uchemical, u.d a b i o t i c ? anorganic, ffl a no l i f e

'G$2 .j 3

a

a n t i s a p r o b i ty

400 7 00 20G0

1000 0

+

+

M

t

' 4

rwt a t r o p h i c i t y

r

12 .lo4

toxic

radiosaprobity r a d i o a c t i v e k

kryp tosaprobi ty physical

Categorization of water q u a l i t y according to its saprobity and t r o p h i c i t y . Relationships of the metabolism, s e l f - p u r i f i c a t i o n processes and the t r o p h i c i t y . Values concerning chlorophyle and p r i m r y production a r e r e l a t e d t o the r e s u l t of the eutrophiza t i o n process.

2

82 TABLE 1.31 Physical and chemical i n d i c a t o r s

p~

Polytypus

Mesotypus

Oligotypus

15- 20 25-100 1- 0 1.5 25- 50

< 15 3- 25 0 0 25

-

N,P,Fe

S m e r temperature j u s t belaw the water t a b l e

> 20

OC

CaO

mg.1-1

Nitrogen

N

mg.1-I

Phosphorus

P

-1 mg. 1

Calcium oxide

>100 )40 >25 80-100

-1

mg. 1

Humus a c i d s Biotypus

Characteris t i c s Occurrence

a 1c a l i troph i c

poor plankton carst

PH )7

Ca

siderotrophic

l i m o n i t i c bed

Fe

a r g i l o trophic

high t u r b i d i t y loamy and s i l t sediments

humus mtter

eutrophic

high content of nutriments r i c h phytoplankton mud, m r s h e s bottom hydrogen sulphide c l e a r water, poor phytoplankton, poor f l o r a i n the neighbourhood new reservoirs, mountain lakes

01igo trophic

acido trophic

t u r f i c bed

dystrophic

browny water, poor phy to-plankton

>7

N,P

N,P

-7

< 5.5 <7

Ca humus matter

Ca,P,N

occasionally r i c h zooplankton marsh without odour hypertrophic

heavily p o l l u t e d water, degrada ted aquatic l i f e

Categorization of water r e s e r v o i r s , t h e i r trophic- and biotypes , physical and chemical i n d i c a t o r s according t o N a m n (1932), completed by Thienemann (1942) and Srdmek/HuSek (1948).

83 1.9 RUNOFF PROCESS AS REGITIATOR OF THE LIVING ENVIRONMENT Basic c h a r a c t e r i s t i c s influencing t h e l i f e and i t s environment gradually change with a c h a r a c t e r i s t i c g r a d i e n t i n the course of the longitudina1 p r o f i l e of the r i v e r . They a l s o have an important impact on the u t i l i z a t i o n of water f o r d i f f e r e n t b e n e f i c i a l uses a s w e l l a s on the ecosystems and the u t i l i z a t i o n of the neighbouring a r e a . Some of these c h a r a c t e r i s t i c s , namely geomrphological and hydraulic, and a l s o s e l e c t e d hydrological c h a r a c t e r i s t i c s , a r e q u i t e independent of the season. The course of the rest depends on the annual season and on the climate, espec i a l l y i n the case of r i v e r s running through d i f f e r e n t climatological zones (Fig. 1.29).

UPPER COURSE

MIDDLE COURSE

LOWER COURSE

Fig. 1.29. The development of b a s i c c h a r a c t e r i s t i c s of a water course represented i n i t s longitudinal p r o f i l e , o f f e r i n g important information f o r the concept of a g r i c u l t u r a l , i n d u s t r i a l and urban development: 1 v a l l e y width, 2 - average discharge, 3 - r i v e r channel s l o p e , 4 - r i v e r channel width, 5 v e l o c i t y of f h , 6 - f l u c t u a t i o n of discharge, 7 - water temperature, 8 - a e r a t i o n , 9 - biochemical and chemical oxygen demand, 10 sedimentation rate.

-

-

-

The s u i t a b i l i t y of a r i v e r s i d e a r e a f o r d i f f e r e n t development purposes can be derived from the course of the mentioned curves by analysing the relevant i n t e r r e l a t i o n s h i p s . Some r e l a t i o n s appear t o be contradictory: Lower and middle course a r e a s a r e more s u i t a b l e f o r the l o c a t i o n of housing and i n d u s t r i a l

84 e s t a t e s due t o the necessary space. From the water supply p o i n t of View, upper courses a r e more s u i t a b l e having more favourable conditions f o r r e s e r v o i r con-

st r u ction. IJpper courses o f f e r a high head and thus more favourable conditions f o r water power generation - with r e s e r v o i r s a s w e l l f o r peak power production. Lower courses with h i g h , sustained discharges o f f e r conditions f o r the construct i o n of run-of-river p l a n t s with lower heads. They o f f e r only r e s t r i c t e d p o s s i b i l i t i e s f o r the construction of r e s e r v o i r s , but favourable conditions f o r inland navigation. P r o t e c t i o n a g a i n s t floods can be achieved more economically by a proper l o c a t i o n of the r e l e v a n t e s t a t e s o u t of the flood p l a i n a t the upper courses i f r e l e v a n t v a l l e y s a r e s u f f i c i e n t l y wide, and by r i v e r t r a i n i n g i n the middle and lower courses. The l o n g i t u d i n a l proportion of the water course i n an open a r e a c r e a t e s a n a t u r a l t r a f f i c a r t e r y : not only i t s channel, but a l s o the r i v e r s i d e s on both banks. Fluctuations i n the water t a b l e l i m i t the b e n e f i c i a l u t i l i z a t i o n of the flooding a r e a f o r cormunication, housing and i n d u s t r i a l estates, which have t o be protected from overflooding. Nevertheless, t h i s zone usually has exceptional climatological and a e s t h e t i c conditions, extremely s u i t a b l e f o r r e c r e a t i o n . I t

i s , t h e r e f o r e , useful t o reserve t h i s zone , e s p e c i a l l y i n c i t i e s , f o r pedes t r a i n c m n i c a t i o n s o r i n d u s t r i a l q u a r t e r s by a zone of p l a n t s o r by a comunication l i n e (Fig. 1.30). C m u n i c a t i o n , r e c r e a t i o n a l , i n d u s t r i a l and housing a r e a s a r e mutually i n t e r r e l a t e d . The l o c a t i o n of a housing e s t a t e i n the second zone is a e s t h e t i c a l l y and f u n c t i o n a l l y favourable when i t corresponds t o the topography, aad provided t h a t flood p r o t e c t i o n measures a r e r e a l i z e d . The fimction of water courses f o r housing and i n d u s t r i a l e s t a t e s i s twofold:

they a r e used a s sources of water supply and a s r e c i p i e n t s of waste disposal. These two functions a r e contradictory. Besides, the u t i l i z a t i o n of water courses f o r waste disposal is contradictory with t h e i r urban and aesthetic functions. The a e s t h e t i c enjoyment of water a s a n i n t a n g i b l e n a t u r a l f a c t o r is manifesta ted i n t h r e e dimens ions

-

i n the water scenery, c r e a t e d by the s y n t h e s i s of the water formation and its surroundings namely r i v e r banks, i n the v i s u a l u n i t - i.e. t h e p a r t of the landscape which i s v i s u a l l y access i b l e from one p l a c e , - i n the landscape u n i t , i . e . formed by a geographically complex a r e a .

-

The a e s t h e t i c p r o p e r t i e s of water a r e formed by i t s prominence, e s p e c i a l l y by its - c o n t i n u i t y and comprehensiveness, - diversity,

-

v i v a c i t y and v a r i a b i l i t y .

85

[

D

C

VILLAGES

IAGRICULTURd

B

t,"sysI RIVER CHANNEL

A

1-1

B ~~~~

C

D

~AGRICULTURE~INTENSIM AGRICULTURE __.

Fig. 1.30. Regulation of flood plain use derived from frequency of flooding and differing i n the t o m and outside the town: A - floodway, B,C: - p a r t i a l l y protected zones, D - protected zone. These properties depend on q u a l i t a t i v e and quantitative factors. The aesthet i c expression of a reservoir o r a s t r e t c h of stream follows from i t s comprehensive continuous form, limited by the diversified bavks, whose edges form limits between the water and riverside ecosystems. I n a built-up area three categories can be distinguished on the basis of the dimension r a t i o of the housing, i n d u s t r i a l , recreational e t c . area t o the width of the water level: (a)

dimensions of the water table a r e not remarkable with regard to the

dimensions of the relevant area, (b) dimensions of the water level do not d i f f e r remarkably from the dimensions of the relevant e s t a t e , (c) dimensions of the water t a b l e exceed the dimensions of the relevant estate. The resulting aesthetic enjoyment depends i n any category on the quality of the architectural s t r u c t u r e , but the medium category o f f e r s the mst favourable conditions f o r an a e s t h e t i c and balanced e f f e c t of the water table i n an urban s e t t i n g . Architectural complexes i n these conditions evoke the strongest aesthetic emtions.

I

86 Chapter 2

W E R AND ITS FUNCTION I N SOCIAL SYSTEMS

2 . 1 CATEGORIES OF WATEB UTILIZATION Water use includes a l l individual and collective a c t i v i t i e s of hum7 society which a f f e c t water resources and change t h e i r quality and quantity. 'Ihe benefic i a l u t i l i z a t i o n of water depends, as does its natural functions, on the water properties. Water uses include (a) in-s tream (navigation, hydropower generation e t c . ) and on-site (ponding e t c . ) uses, without withdrawing water from the resources, (b) water withdrawal, i . e . diversion of water from the surface o r groundwater resource - local, i . e . on-site use i n the neighbourhood of the resource, - collective mss use by means of complicated supply, distribution and drainage (sewerage) networks. The method of water use and distribution depends especially on the degree of development and organizaticn of the social system. I t becomes s y s t e m t i c as a consequence of a g r i c u l t u r a l , social and industrial development, gradually creating more extensive and complicated networks f o r water conveyance, distribution, use and drainage. Fran the beginning water has been the basic need and precondition of h m n existence, but gradually i t has a l s o become a raw material which has been turned i n t o a means of development i n i t s e l f . An e f f i c i e n t water use i n an organized society is mnaged by means of licences and concessions. Generally, no licence is required for non-organized small-scale water withdrawals and in-s tream uses, especially individual, on-site washing, bathing e t c . , which is considered as a general use of water (Tab. 2.1). Water supply includes a l l organized a c t i v i t i e s for the use of withdrawn water. I t s purpose is t o ensure the necessary water quantity of the required quality a t the requested place i n terms demanded by water users, i . e . by the (a) population (municipal and r u r a l demand), (b) agriculture and forestry, (c) industry and infrastructure (especially energetics and transport). The functions of water can be categorized as natural and s o c i a l i . e . water demands - in-stream, on-site uses and withdrawals. The relevant categories of water demands have a c h a r a c t e r i s t i c impact on water quality and quantity (Tab. 2.2).

87 TABJX 2.1

III

I Natural functions

I1 In-s tream uses

S o i l moisture conservstion, s o i l

Groundwater t a b l e

trans f o m t i o n

r e g u l a t i o n HC

Transport o€

Waste t r a n s p o r t

Other domestic

biogeoelements

& disposal

uses

& s o i l moisture

HV,

Wi thdrawals Drinking & cooking HQ

w ,w

-

Y.

r i

HQ, HP

Biological

F i s h and wild-

Public uses

f unc t i o n s

life

HQ, HP

Regulatory c l i -

General u t i l i z a -

Heating, steam power,

matic functions

tion

b o i l i n g , c lima t iza-

v)

SR

Lc

tion

HP, HC

Aesthetic enjoyment

Water t r a n s p o r t

Processing

Other environ-

Hydropower genera- Cooling

mental functions

t i o n IW, LQ, LC

IIV, LQ, HC

Recreation &

Mining & h y d r a u l i c

water s p o r t s LC

transport

public & goods

HP

~~

LQ

Hp,

Other i n d u s t r i a l & a g r i c u l t u r a l uses LV

Irrigation HV, HC Processing

HP Livestock ti poult r y breeding HP Fish & water fowl breeding Categorization of n a t u r a l function of water and of water u t i l i z a t i o n . Abbreviations : Consumptive use Quality requirements Impact on water q u a l i t y Volme requirements High space requirements

HC HQ HP

- high - high

- high

HV - high SR - high

u: -

low

rQ - low LP - low

LV

- low

88

2.2

WATER REQUIREMENTS AND WATER CONSIJMFTION The term water resources r e f e r s t o the e x p l o i t a b l e s u r f a c e water and ground-

water i n a defined water management u n i t ( e . g . catchment b a s i n ) . Because of t h e i r p e r i o d i c annual replenishment, the most s u i t a b l e u n i t f o r t h e i r d e f i n i t i o n is the m3 per year (dry, wet, mean) which leaves the r e l e v a n t water management u n i t . The s t a t i c i n t e r p r e t a t i o n is the amount of s u r f a c e water o r groundwater

(m3 ) w i t h i n the water resource. TABLE 2 . 2 Quantity

\dater q u a l i t y (properties)

Other f a c t o r s

Vo lume

physical ch e m i ca 1 bioch e m i ca 1

water t a b l e width

(m3 ) Discharge (m3. s-1)

b iologica 1

Runoff (m3. s-l)

(phys i o logica 1)

-

bacteriological radiological

total yearly seasonal

riverbed width channel depth groundwater t a b l e depth water t a b l e f l u c t u a t i o n v e l o c i t y of flow sediment t r a n s p o r t

- average

organolep tic

icebound regime

- minimum - maximum - minimum - fluctuation

(sensoria 1)

a c c e s s i b i l i t y of shores u t i l i z a t i o n of the r i v e r s i d e

psychic medical ( s a n i t a r y )

shore vegetation bank p r o t e c t i o n

Basic parameters of water occurrence and f a c t o r s determining the p o s s i b i l i t i e s of water u t i l i z a t i o n . The amount of water d i v e r t e d from the water resource i n a given period is the m3 p e r y e a r ) . The water withdrawal is the input of the water withdrawal Crr~~.s-~, water supply system. The q u a n t i t y of water returned t o water resources a f t e r use (with a changed q u a l i t y ) i s r e t u r n flow. I t forms the output from the supply and drainage system. The q u a l i t y of the r e t u r n flow i s i n f e r i o r i n comparison with the q u a l i t y of the withdrawal due t o t h e processes of water use.

A given water requirement is t h e amount of water which is necessary f o r the undisturbed course of any n a t u r a l o r technological process. It includes water consmption (consumed flow), i . e . t h e d i f f e r e n c e between water withdrawal and the n e t r e t u r n flow, that c o n s i s t s of consumptive use and losses. The consumptive

use of water r e p r e s e n t s that p a r t of t h e water consumption which, i n the course of the n a t u r a l o r technological production process, becomes an i n t e g r a t e d p a r t of

a9 (a)

t h e product o r t h e by-product o r t h e waste matter.

(b) The water loss r e p r e s e n t s t h a t p a r t of the water requirement, water consmpt i o n , water withdrawal o r water resource which r e t u r n s i n t o the hydrologic cycle i n the form of seepage, leakage, p e r c o l a t i o n , evaporation e t c . Losses may be either ( a ) productive, i .e

. indispensable

f o r the course of the production process

( e . g . evapotranspiration f o r the a g r i c u l t u r a l production), o r (b) non-productive, a p a r t of which is i n e v i t a b l e , i . e . l o s s e s which cannot be supressed i n a r a t i o n a l or economic

-

way, and t h e rest is - the wastage, i . e . water t h a t escapes from the resource, t h e supply system o r the production process without being used.

The consumptive use (consumed flow) can be expressed by the following simple equation C=W-(F-B) (1.s -1 , m3 .s -1) (2.1)

c - w a t e r consumption W - water withdrawal (F

F

- B) - n e t r e t u r n flow - r e t u r n flow a t the end

of the sewerage system

B - undesired inflow i n t o the sewerage system (drainage of groundwater, conveyed springs e t c . ) From the foregoing terminological d e s c r i p t i o n it a l s o follows t h a t

(1.s

-1

,

3

)

(2.2)

U1 - consumptive use by means of t h e product ( e . g . f r u i t ) U

2

U

3

-

consumptive use by means of the by-product (e.g. trunk, branches, leaves)

- consumptive use by means of the waste material (e.g. weeds)

A 1 - productive l o s s e s (e.g. evapotranspiration)

A2 - non-productive i n e v i t a b l e l o s s e s ( e . g . leaching, seepage i n i r r i g a t i o n piping)

(4) (Ai )

A3

-

non-productive e v i t a b l e l o s s e s caused by t h e state of system o r by the i n s u f f i c i e n t technology e.g. seepage and evaporation i n i r r i g a t i o n c a n a l s )

A4

-

non-productive wastage caused by wrong operation

(%)

The r e t u r n flow, except f o r t h e undesired inflow i n t o the system, which was used i n the production processes and occasionally a l s o water which was necessary to d i l u t e t h i s water from the production processes w i t h the aim of achieving the

90

desired water quality of the waste water before returning i t i n t o the water resources can be expressed as follcws F = F ( + F 2 ) + B 1

(2.3)

F

-

F1

- waste

F2

-

d i l u t i o n water

B

-

undesired o r occassional inflow i n t o the system.

return flow (diluted waste water) water from the production process

The consumptive use of water entering the product i s thus the key constituent of water requirements. The quality of the product depends on the technology, which a l s o determines the consumptive use of the water entering the by-product o r the waste material, upon which the econany of the production a l s o depends. The economy of the production process, from the water management point of view, can be improved by decreasing the amunt of waste material, or by decreasing the s i z e of the product, i f possible. F r m the point of view of the balance of water resources and needs the most important problems are the changes i n the water quality and a l s o the place of discharge of the return flow and the return of losses i n t o the water resource (Fig. 2.1). Consequently losses can be c l a s s i f i e d i n the following way: (a)

-

return losses which enter

the same water resource from which the water was withdrawn

Arl Ar2 water resources i n sane other catchment basin ‘r3 (b) non-returnable losses (evaporation and evapotranspiration) which escape other water resources i n the same catchment basin

from the relevant resources and enter the atmosphere. An Water consumption, defined a s the difference between the withdrawal and the return flow, can thus be expressed as follows:

c

=

& izl u i

+

i=l ? A

ri

+

4

(2.4)

The mathematical definition of water consumption varies according to the water balance of d i f f e r e n t systems. Frcm the point of view of the particular water resource, the water consumption Cr does not contain the f i r s t return loss

-

the return loss entering the water resource from which the water was with-

drawn

cr =

.&

& (2.5)

91

Fig. 2.1. Schematic representation of water use a f t e r physical diversion during an i n d u s t r i a l or biological process, which r e s u l t s i n production, accompanied by consumptive use by the product U1, by-product U and waste material U 3 a s well a s by water losses Al-nt. The use of the pro$uct, resulting i n i t s change into wastes and the decomposition of wastes can lead to water recovery U,: Waste waters from the production process a s well a s the leached wastes cause water pollution.

From the point of view of the catchment basin, the value of the water consunr ption $ includes n e i t h e r the f i r s t nor the second return loss

From the point of View of the hydrologic cycle, the water consumption Cc is formed only by the consumptive use:

cc

=

f u; i=l

'Ihe consumptive use is ( a ) short-term ( t r a n s i e n t , l a s t i n g several days o r years) (b)

l o n r t e r m ( a l s o from the point of view of geological time) or l a s t i n g

(stable chemical l i n k s ) .

92

There fore

fl-3

-

t

- time

n

1-3

variables

- coefficients of the time e f f e c t

The mentioned general process not only occurs i n the course of the municipal, r u r a l , industrial and agricultural water supply, but a l s o during the natural production process of different biological functions and during the development of c e l l u l a r matter. Waste matter from the natural and technological processes, also formed by the u t i l i z a t i o n of the products, usually disintegrates and releases water which also enters

the hydrologic cycle. The growing of c e l l u l a r rratter such as wood, peat,

coal, o i l e t c . causes long-term consumptive use. The increase i n quantity of c e l l u l a r m t t e r m y theoretically r e s u l t i n the consumption of a l l the water resources available i n a certain area, but the homeostasis, i . e . the dacay of c e l l u l a r m t t e r e t c . l i m i t s this undesired development. Water requirements and water consumption i n the course of agricultural and industrial processes may be distinguished as (a)

minimum,

(b)

optimum,

(c)

non-economic.

Minimm water requirements or minimum water consumption during a specific production process can be achieved under special conditions, e.g. i n laboratories. The watersaving technology which achieves the minimum water requirements m y d i f f e r from the technology which achieves the minimum consumption of water, and both can be unsuitable from the point of view of the t o t a l production c a s t . An optimum water requirement and optimum water consumption a r e attained when the product of desired quality i s produced under the conditions of minimum t o t a l social e f f o r t , i . e . from the point of View of the national economy, by applying an optimum technology. R e non-economic water requirements and water consumption exceed t h i s optimum value. Low losses and optimum water consumption a r e indispensable preconditions for any e f f i c i e n t industrial. technology. Low water requirements depend primarily on the degree of recirculation. An e f f i c i e n t water resources management policy is based on a decrease i n water consumption and an improvement i n the waste water qua li ty

.

The prevailing, productive, non-returnable losses form the indispensable precondition for the efficiency of agricultural processes. The efficiency of water

93 u t i l i z a t i o n i n a g r i c u l t u r e can be folluded up, f i r s t , on the b a s i s of the r a t i o of the productive evapotranspiration and non-productive l o s s e s

a,

xe =

.g. i=2

and, second, on the b a s i s of thp r a t i o of the consumptive u s e e n t e r i n g the product and the consumptive use of the o t h e r c e l l u l a r r m t t e r : xu =

2.3

u2

IJ 1 +

(2.10)

u3

IN-STRFss.I ANI, ON S I E IJATER USE On-site u s e s , such a s s o i l moisture conservation, flood loss management, the

maintenance of swamps, dambos and o t h e r wetlands a r e c l o s e l y interconnected with the n a t u r a l functions of water. In-stream uses such a s h y d r o e l e c t r i c power generation, navigation, r e c r e a t i o n , water s p o r t s and waste disposal a r e c l o s e l y connected with the s o c i a l functions of water. In-stream uses a r e characterized by i n s i g n i f i c a n t consmption. The only water consumption m i n l y c o n s i s t s of l o s s e s . For these uses the volume of water is important, and not the discharges. The a p p l i c a b l e u n i t of measurement i s m3 The water consumption c o n s i s t s of

.

r e t u r n l o s s e s nr3 which e n t e r o t h e r catchment basins and nqn-returnable losses

(2.11) (2.12) V

- volume of water necessary f o r the in-stream o r on-site use of water

w -

t o t a l water requirements

These equations can be extended t o express the n a t u r a l functions of water i n the following way

w

=

c =

v

+I [

(U1+U2

+

u3

+

( lJ1

-+

113

+

+

6

Ar3

+

Ar3

+

1:

A n ( m3)

(2.13)

A n (m3)

(2.14)

Losses due t o t h e in-stream use of water should be considered a s the d i f f e r ence between the values before use and t h e values of l o s s e s occuring during in-stream use. These losses c o n s i s t of leakage and conveyance i n t o o t h e r catchment basins a s a r e s u l t of b e n e f i c i a l operation, and of evaporation and seepage

94 due to the extended water t a b l e and enlarged r i v e r channel, when necessary f o r the r e l e v a n t use.

2.3.1 Waste Disposal The hydrosphere is used f o r waste disposal and enables, prirrarily i n water courses, the t r a n s p o r t a t i o n and removal of wastes . Waste waters and waste materials which a r e conveyed i n t o s u r f a c e and groundwater bodies e n t e r the n a t u r a l processes of t h e generation of water q u a l i t y , enabled by the t h e m l , chemical and k i n e t i c energy of water, by the thermal and chemical energy of the r i v e r b e d , and by the thermal and luminous energy from the environment of t h i s system. TABLE 2 . 3 ~~

~

Phys ica 1

Processes Chemical

Biochemical, b i o l o g i c a l

warming - coolinp

neutralization

aerobic d i s i n t e g r a t i o n

disintegra tim

oxidation

anaerobic d i s i n t e g r a t i o n

mixing, dispersion

reduction

ass imila t i o n

dillution

coagulation

dissimilation

sed imen ta ti on

biological f i l t r a t i o n

adsorption, d e 5 0 t~ion

adsorption of low organism

washing away oxygen exchange

by higher ones decay of l i v i n g mtter

Oxygen d i f f u s i o n Categorization of basic processes of water s e l f - p u r i f i c a t i o n .

The e r o s i o n , f a l l - o u t and waste d i s p o s a l r e s u l t s i n an increase i n bed load, suspended load and dissolved rratter along the water course. But a complex of other p h y s i c a l , chemical, biochemical, b i o l o g i c a l and b a c t e r i o l o g i c a l processes a s a m n i f e s t a t i o n of the homeostasis i n n a t u r e f u r t h e r changes the water q u a l i -

ty. S e l f - p u r i f i c a t i o n processes accompany t h e water p o l l u t i o n process i n the course of sediment t r a n s p o r t and e r o s i o n processes, r e s u l t i n g i n the d e s t r u c t i o n and melting of e r o s i o n products, waste m a t e r i a l and f a l l - o u t (Tab. 2.3, Fig.

2.2).

95

evaporation, heat

heat, kinetic and chemical eneray

fall-out, erasion products, effluents

SEDIMENTS

I

radiation, cloudiness, temperature,wind,humidi ty

I

OXYGEN

WATER QUALITY INDICATORS

Fig. 2.2. Schematic representation of water self-purification process, a subsystem of biogeochemical cycles. Input consists of matter and energy, output is formed especially by sediments, benthos, water vapour, heat and water quality, characterized by a s e t of indicators. The indispensable precondition f o r the destruction and transport of t h i s material is a surplus of k i n e t i c energy (see Chapter 1.6). A lack of k i n e t i c energy causes sedimentation, the most basic of the physical self-purification processes. S e d h e n t a tion is governed by Stokes ' s law:

, .y

w = 0,Ol

( G I )

w - v e r t i c a l sedimentation r a t e

(m.s-'>

8 -

diameter of sedimented p a r t i c l e s

(m)

u n i t mass of p a r t i c l e s

(kg m-3)

d

.

a , n - c o e f f i c i e n t s of s i z e , depending on the diameter of p a r t i c l e s d

(0.002 m

-n

=

1.2

; a = 0.07

(2.15)

96

-

d >0.002 m

: a

n = 2

= 0.064

Sedimentation is accompanied by coagulation and melting and r e s u l t s i n a decrease i n the content of chemical matter i n water and i n an increase i n the sediment volume. Another b a s i c process of self-purification to occur a s a r e s u l t of the cont a c t of water with the a i r is the acceptance and diffusion of oxygen. Oxygen e n t e r s water not only from the a i r , but a l s o a s a product of the biological processes of plants and of phytoplankton. The content of dissolved o x y p n i n water is limited by temperature, barometric pressure and by the content of oxygen i n the a i r above the water surface: R cb = 0,373 H

.-

cb

-

(2.16)

dissolved oxygen balance i n water, when the Oxygen content i n the a i r equals 21%

R - barometric pressure H

- Henry's

(Pa)

constant, depending on water temperature (Pa- Tab. 2 . 4 ) .

TABLE 2 . 4 Temperature

(OC)

(1O;'Pa)

H

0

5

10

15

20

25

90

2.57

2.95

3.32

3.69

4.05

4.44

4.81

Henry's constant H f o r the determination of the oxygen content i n water i n dependence on water temperature

.

Chemical. processes of self-purification,

decomposition, coagulation, neut-

r a l i z a t i o n a s well a s absorption and desorption consume t h e dissolved oxygen, r e s u l t i n g i n an oxygen deficiency, expressed by the difference between the a c t u a l oxygen content and the oxygen balance which corresponds t o the relevant temperature

.

The r a t e of the n a t u r a l l i q u i d a t i o n of t h i s deficiency depends expressly on the temperature, and on the current velocity and depth of the water. StreeterPhelps (1925) prove t h a t the process of reaeration is quicker i n shallow r i v e r beds with a higher current velocity: Dt

x = K2

*

Dt

D t = D o . e - K2T

K2 = 1,047 (T-20)

(2.17)

K2(20)

97 Dc

-

oxygen deficiency a t the beginning of the reaeration (g.m-3)

.

(g m-3 )

D t - oxygen deficiency during the reaeration

-

t

K

2

time

(d-3

- coefficient of reaeration a t the temperature T

-

K

2(20) T

(d)

-

coefficient of reaeration a t the temperature of 2OoC (Tab. 2.5)

(d-')

temperature

(OC)

TABLE 2.5

Coefficient K2 (d-I)

Type of water course Shallow brook

0.50-0.80

River: velocity of flow)0.5 m.s-' (0.5 m.s-l

0.30-0.80

Reservoir

0.05-0.15

0.20-0.25

Coefficient of reaeration K2 a t 20°C according t o Zhukov (11964) In the course of physical and chemical processes the suspended matter is swallowed down by water organisms. The absorption of t h i s matter into the nutrition chains of des truents , consumers and producers changes the living organic m t t e r into anorganic m t t e r and vice-versa. Most of the mentioned processes a r e aerobic , i . e . require the presence of oxyge?. Anaerobic processes , i . e . processes without oxygen, occur especially near the bottom, i n the mud. The r a t e of the biochemical decomposition of organic mtter depends on the enzymatic systems of the relevant organisms, i . e . their a b i l i t y to decompose certain organic matter, o r on their a b i l i t y to create such systems a f t e r a short period of adaptation. The process of biochemical oxygen demand during biochemical decomposition can be described by the equation of kinetics of the 1st order Lt = Lo.( 1

-

e

-K t 1)

K1 = 1,047 ( T -20 ) Lt

- biochemical

Lo

- the

K1

- coefficient

K1(20)

-

(g.m-3 )

(2.18)

. Kl(20)

oxygen demand i n the period t

(BOD)

(a~m'-~)

i n i t i a l value of the biochanical oxygen demand ( g m-3 ) of deoxygenation a t the temperature T

coefficient of deoxygenation a t 20°C

(d

-1

)

w-5

98 The change i n the value of the oxygen deficiency during the processes of r e a e r a t i o n and deoxygenation, i . e . during the biochemical d i s i n t e g r a t i o n of organic m a t t e r , can be expressed by the d i f f e r e n t i a l equation

(2.19) D' - oxygen deficiency a t the moment t f o r the simultaneous r e a e r a t i o n and biochemical d i s i n t e g r a t i o n of organic matter. The decrease i n the oxygen concentration and the i n c r e a s e i n i t s deficiency a s a consequence of the simultaneous reaera tion and deoxygenation l a s t s u n t i l the c r i t i c a l moment a t which the r a t e of the biochemical oxygen demand and the r a t e of the oxygen i n p u t become equal. A f t e r reaching t h i s c r i t i c a l moment, t h e concentration of oxygen rises t o the o r i g i n a l value, following the curve of the oxygen content. I f t h e concentration f a l l s below the c r i t i c a l l i m i t , t h e organisms d i e (Fig. 2.3). The beginning of t h i s process i s accompanied by a decrease i n the v a r i e t y of b i o l o g i c a l species , c h a r a c t e r i s t i c f o r the degree of oligosaprobity, due t o q u a l i t a t i v e and q u a n t i t a t i v e changes i n the l i t t o r a l and benthic fauna, and i n the plankton and f i s h s p e c i e s . Consequent changes i n the water p r o p e r t i e s include t h e change i n i t s colour, t h e decrease i n t u r b i d i t y , the decrease i n the oxygen c o n t e n t , e s p e c i a l l y i n the hypolimnion of r e s e r v o i r s etc. A f u r t h e r surplus of nutriment supply then causes

a d e t e r i o r a t i o n i n the water q u a l i t y a s a r e s u l t of the development of some organic species (Anabaena, aphanizmenon flos-aquae e t c . ) . Tne r e s u l t of t h e i r d i s i n t e g r a t i o n a f t e r e x t i n c t i o n i s a n exhausted oxygen content. Water p o l l u t i o n which occurs a t the same place changes i n time and depends on the p o l l u t i o n regime, the r e l e v a n t discharges , the morphological f a c t o r s of the r i v e r channel, the c l i m a t o l o g i c a l f a c t o r s and the coherent course of the s e l f p u r i f i c a t i o n processes. Water p o l l u t i o n can a l s o be defined a s a complex of processes whose r e s u l t l i m i t s o r makes impossible t h e b e n e f i c i a l use of water. The n a t u r a l p o l l u t i o n of s u r f a c e water i s g e n e r a l l y low - t h e water q u a l i t y varying w i t h i n the limits of the 1st o r 2nd class of water q u a l i t y - unless i t is severely d e t e r i o r a t e d by higher q u a n t i t i e s of suspended matter ( e s p e c i a l l y by washed s o i l p a r t i c l e s a f t e r heavy r a i n f a l l , o r by high contents of s a l t s a s a r e s u l t of s a l t plugs i n the r i v e r channel o r high evaporation - Tab. 1.24). The c h a r a c t e r of water p o l l u t i o n which is caused by the i n d u s t r i a l , agricult u r a l and o t h e r a c t i v i t i e s of h w a n s o c i e t y and by urban e f f l u e n t s d i f f e r s frcm

99 'eosible or

Economically unfeasible for drinking water

water

iection )issolved oxygen luctuation ( 0 - 2 4 h)

O b 2 4

Sche mat ic .epresentotion h c r e o s e in sxygen :ontent

"

I

0 xygen content tion

urification

-----

Eoncentration 3f oollution Zhorocteristics

pogenetic pollution

pollution

Prevailing pollution

Natural

Wastewaters Natural waste waters in low in high concentration concentration

Jrevai Ii ng processes

Physical

Saprobity

Oligo- saprobity 6 -mesosaprobiry

Hetemtrophic biologicoi oxidation, reduction, destruction of dead organic matter

MesoPoly saprobity

pollution

Autotrophic, biological production of living matter

.______ B -mesosoprobity d-mesosaprobity

,

pollution

;econdor y )ollution

See B,

See C,

See B,

See C,

See B,

See

C,

Fig. 2.3. Schematic r e p r e s e n t a t i o n of the course of the main c h a r a c t e r i s t i c s of the s e l f - p u r i f i c a t i o n process i n the longitudinal p r o f i l e of a water course with a cascade of r e s e r v o i r s . Both n a t u r a l and anthropogenetic p o l l u t i o n increases downstream. A c h a r a c t e r i s t i c curve of oxygen demand appears below the e f f l u e n t s . t h a t of n a t u r a l p o l l u t i o n . This p o l l u t i o n considerably changes the chemical and b i o l o g i c a l p r o p e r t i e s of the water, and a l s o the type of the relevant chemical, b i o l o g i c a l and o t h e r processes. A decrease i n water q u a l i t y below the 3rd o r 4th c l a s s is a frequent consequence a s w e l l a s eutrophosation, r e s u l t i n g i n a decrease i n the b i o l o g i c a l q u a l i t y of w a t e r , reaching a maximrun of

8-

mesosaprobity (Tab. 1.24, 1.30). The s e l f - p u r i f i c a t i o n process, l i k e any manifestation of n a t u r a l homeostasis, is stimulated by feedbacks. But the state t o which the system r e t u r n s is not n e c e s s a r i l y the same a s the o r i g i n a l one. The lack of energy o r matter makes such a return impossible and r e s u l t s i n a n i r r e p a r a b l e change i n water q u a l i t y which may l i m i t o r exclude its b e n e f i c i a l we. The acceptable q u a l i t y of water i n a water resource can be expressed f o r any p a r t i c u l a r use by a set of indices.

100 A l l these chemical, biochemical and b i o l o g i c a l processes occur i n the environ-

ment of the running water. Suspended matter and f l o a t i n g debris of both n a t u r a l and anthropogenetic o r i g i n a r e c a r r i e d away by t r a c t i n g forces of the flowing water. S o l i d wastes i n the stream channel and t h e bed load start t o move when the drag forces exceed the f r i c t i o n forces. The balance of these forces is expressed by the equation

(2.20) F

-

s u r f a c e of the p a r t i c l e under t h e a c t i o n of drag forces (m2 ) (kg .m-3 )

?? - u n i t mass of water vo

-

V

- volume of s o l i d waste/sediment p a r t i c l e

S

-

bottom c u r r e n t v e l o c i t y

u n i t mass of the p a r t i c l e

f

- c o e f f i c i e n t of f r i c t i o n

g

- gravitational

constant

(m. sm2)

The c u r r e n t v e l o c i t y , the s i z e and shape of the p a r t i c l e s o f n a t u r a l and anthropogenetic o r i g i n a s w e l l a s t h e i r u n i t mass is not uniform throughout the cross s e c t i o n . For p r a c t i c a l reasons the beginning of the motion of a s i g n i f i cant q u a n t i t y of sediments is important, which depends on a c r i t i c a l v e l o c i t y corresponding t o a c r i t i c a l discharge a t which the above equilibrium (Eq. 2.20) is disturbed. Tne c r i t i c a l bottom c u r r e n t v e l o c i t y which c h a r a c t e r i z e s the start

of the motion can be derived from, the above equation a s follows

(2.21) vC

- criFical

bottom c u r r e n t v e l o c i t y , c h a r a c t e r i z i n g the start of the sediment

motion V

d =2 Fs

- characteristic

e f f e c t i v e s i z e of the p a r t i c l e s

me discharge corresponding t o t h i s c r i t i c a l b o t t m c u r r e n t v e l o c i t y i n the conditions of most sustained r i v e r beds is o f t e n t h e discharge exceeded 50% of the t i m e , i . e .

Q,,,,.

The water q u a l i t y due to the course of sediment movement and the d i l u t i o n of waste waters depends on the discharge b u t i n d i r e c t r e l a t i o n s h i p with: (a)

s o i l - e r o d i b i l i t y r a t e , dependent on p r e c i p i t a t i o n , and

(b)

s o i l - s o l u b i l i t y r a t e , dependent on t h e i n t e n s i t y of the s u r f a c e runoff,

( c ) geological, s o i l and s o i l s u r f a c e f a c t o r s i n c l . the type of the veget a t i v e canopy, its state and season,

101 (d)

hydrometeorological, seasonal and purely random i n f l u e n c e s , e.E. the

changes i n water temperature , the i n t e n s i t y of s o l a r r a d i a t i o n , the i n t e n s i t y of the l o n g i t u d i n a l mixing which determine the w h i r l i n g and transport of sediments and wastes a s well a s the course of n a t u r a l processes of s e l f - p u r i f i c a tion, (e)

anthropogenetic a c t i v i t i e s , i . e . the p o l l u t i o n regime.

The p o l l u t i o n regime depends on t h e type of p o l l u t e r s i n question, which m y be ( a ) a c c i d e n t a l ( p o l l u t i o n from p i p e l i n e s , t r a n s p o r t vehicles and t h e i r f r e i g h t , breakdowns e t c . ) , sys term t i c

(b)

- s p o t p o l l u t i o n ( p o i n t p o l l u t i o n ) , i . e . p o l l u t i o n frm c m u n i t i e s , l o c a l i t i e s ,

townships, tams, i n d u s t r i a l and a g r i c u l t u r a l e s t a t e s , i n f r a s t r u c t u r e , s a n i t a r y , school, r e c r e a t i o n a l and o t h e r f a c i l i t i e s ,

-

a r e a l p o l l u t i o n , i . e . washed s o i l s and f e r t i l i z e r s , p e s t i c i d e s , dumps e t c . I n a d d i t i o n t o t h i s organic and anorganic p o l l u t i o n m y be distinguished, the

f i r s t being mostly b e t t e r coped with during n a t u r a l processes. Spot p o l l u t i o n , with the exception of dumps, occurs h e d i a t e l y . Areal p o l l u t i o n , which may a l s o include p o l l u t i o n from dumps, i s generally delayed and depends on the r a i n f a l l , and on the overland and groundwater flow occurrence. I n t h i s connection the r e l e v a n t delay may depend on meteorological f a c t o r s , but may a l s o appear almost independently. Water p o l l u t i o n which occurs a t the same place changes, t h e r e f o r e , i n time.

Tne water q u a l i t y i n s u r f a c e courses which r e s u l t s from the p o l l u t i o n and n a t u r a l s e l f - p u r i f i c a t i o n processes is a function of space and time

IQ

ql,,=f qla

- water

Q

-

x,y,z,

t

-

9

x

9

Y

z

quality indicators

(g.G3)

(m3.s-I)

discharge

-

(2.22)

t)

9

coordinates : x

-

y

-

d i s t a n c e i n the longitudina1 p r o f i l e (from the point of p o l l u t i o n ) (m) l o c a t i o n i n the cross s e c t i o n of the r i v e r bed (m)

z

-

depth of t h e sampling

time

(m) (date,hour)

Under a s i m p l i f i e d approach primarily i n the proximity of the sources of p o l l u t i o n the concentration of d i l u t e d matter can be considered a s a representa-

tive f a c t o r of the water q u a l i t y : q l = a +

b

P

102 q1 - t o t a l concentration of d i l l u t e d mtters i n water Q

-

a

- concentration of the b a s i c n a t u r a l p o l l u t i o n , o f t e n independent of the discharge ( g m-3 )

b

-

(m3.

discharge

s-')

.

p o l l u t i o n ( i n p u t of wastes)

(8.S-l)

I n many p r a c t i c a l cases p o l l u t i o n grows with discharges and the degree of dependence of the concentration of p o l l u t i o n on discharges is l i n e a r q2 = a + d

.Q

(2.24)

o r b i l o g a r i thmic

.

log q2 = log a + d

(2.25)

log Q

The changes of the organic p o l l u t i o n indicator, i . e . of the biochemical

oxygen demand (B0D) and the chemical oxygen demand (COD), can be expressed by the regression formula A

q3 = qb

+

0

+ B

.

10-Klt

(2.26)

q3 - biochemical o r chemical oxygen demand

I

qb

-

b a s i c value of the biochanical o r chemical oxygen demand, dependent on the c h a r a c t e r i s t i c of the catchment basin ( g .m-3 )

A

-

organic p o l l u t i o n , non-degradable by s e l f - p u r i f i c a t i o n processes ( g . s -1 )

B

-

organic p o l l u t i o n , degradable by s e l f - p u r i f i c a t i o n processes

K1

-

c o e f f i c i e n t of deoxygenation

t

- regression

(g.s-l)

(dw1)

t i m e , i . e . the time of advancement of the p o l l u t i o n from the sources of p o l l u t i o n to the analysed p r o f i l e , depending i n d i r e c t l y on the discharge

r ,m

- coefficient

of t h e p o l l u t i o n advancement

Suspended matter and the b a c t e r i a ( c o l i ) can be quant f i e d by the equation b q 4 = a + Q- + d . Q a

-

( n . m -3 pc.m3) (2.27)

q u a n t i t y of suspended matter o r bacterium c o l i from waste waters

.

( g s-'

,pc .m-3)

The changing inputs of the s e l f - p u r i f i c a t i o n process and i t s changing intens i t y r e s u l t i n the changing i n t e n s i t y of the p o l l u t i o n and i n v a r i a t i o n s i n i t s

103 concentration. The change i n concentration may o f t e n be expressed by the equation q i = a +

A 4

qi

-

concentration of d i l l u t e d matter i n the p r o f i l e i

a

-

concentration of the b a s i c n a t u r a l p o l l u t i o n , ind pendent of the discharge k. 1

b

-

concentration of the s p o t p o l l u t i o n , changing with the discharge

Q

- discharge

4

(c.m3 )

(m3. s-l)

coefficient p = f (x , Q , T , h , v ) , depending on the d i s t a n c e x from the source of p o l l u t i o n , discharpe Q , water temperature T, average water depth h i n the r i v e r channel, flow v e l o c i t y v.

p - reduction

On the b a s i s of the foregoing formula the probable deviation of concentration

a t the same place f o r one s i n g l e source of p o l l u t i o n is a s follows (2.29)

pi Qo cq

deviation of concentration i n t h e p r o f i l e i deviation of the b a s i c p o l l u t i o n

, cB ,

cb

- coefficient

of t h e v a r i a t i o n of the discharge, of the reduction c o e f f i c i e n t and of the s p o t p o l l u t i o n

?he hydrometeorological and anthropogenetic inputs of the self-purif ica t i o n system a r e matter and energy. The output is n o t only the water q u a l i t y and sediments, b u t a l s o evaporation and e x t e r n a l temperature, i . e . f a c t o r s which inf luence the microclirna te. 2.3.2

Inland Water Transport

Navigable o r canalized water courses including r e s e r v o i r s and canals form an i n f r a s t r u c t u r e f o r t h e t r a n s p o r t a t i o n of goods and passengers (public, occasional transport including r e c r e a t i o n ) . The c u r r e n t importance of inland water transport is primarily a r e s u l t of i t s energy and manpower saving technology, e s p e c i a l l y with regard t o its r o l e i n conveying individual types of cargo, which is mainly Eeneral, l i q u i d , bulk, heavy, spacious and containerized, such as g r a i n , fodder, timber, c e l l u l o s e , s t o n e , g r a v e l , sand, b u i l d i n g m a t e r i a l s , o r e , coal and coke, o i l and o i l products, chemical products, f e r t i l i z e r s and piece goods. European waterways can be c l a s s i f i e d i n t o s i x c l a s s e s depending on the s i z e and capacity of goods-carrying inland-waterway v e s s e l s (Tab. 2.6). The parameters of waterways a r e derived from t h e s i z e of t h e t y p i c a l motor cargo vessel

104 TABLE 2.6

Class

Capacity ( t )

Class

I.

250 - 400 400 - 600 650 - 1000

IV.

11.

111.

Capacity ( t )

1000 1500

V.

- 1500 - 3000 > 3000

VI .

Classification of European waterways. and motor-driven tug. 'Itro categories can be distinguished on the basis of the biggest vessel (a)

European

(b)

Local

-

vessel E ( 82

.

vessel L ( 41

.

11.4 m ) 5.7 m )

The admissible draught on a canalized water course depends on the water stage: (m)

T = Hp - H d - M T

-

admissible draught of the vessel

(m)

H F: Hd

-

gauged water stage

(m)

M

- margin -

(2.30)

difference between the maximum draught and the gauged water stage (m) safety distance between the vessel bottom and the channel bottom

In the case of inland waterways with a fluctuating water table, the draught characteristic corresponds t o the draught secured during 240 days i n a hydrologically mean year. The network of inland waterways includes (a) (b)

r i v e r channels (natural, improved

-

trained, canalized)

canals ( a r t i f i c i a l water courses).

The basic parameters of these waterways, i.e. those which determine the carrying capacity, include the breadth and depth of the fairway, the corresponding minimum s i z e of the cross section, and the velocity of the flow. The other main dimensions determine the fluency, methods of operation, speed and safety of transport

.

The c r i t e r i a f o r a n assessment of the minimum dimensions a r e as follows (Fig. 2.4): (a) minimmn breadth of the fairway along s t r a i g h t stretches ( a t the level of bottom of the typical vessel): B = 2 b + 2 b'+ b"

(m)

(2.31)

105

Fig. 2 . 4 . Schematic cross section of an inland waterway. The relevant parameters are t o be derived from the parameters of the typical vessel. B

-

minimum breadth of the fairway

b

-

vessel width

b'

-

board space space between vessels

b"-

minimum breadth of the fairway i n a curved s t r e t c h

(b)

e

(2.32)

(m)

B ' = B + e

extension in curves n

L

- overall

length of the typical vessel formation

R - perimeter of the curve A

-

coefficient of the extension ( =

L* T

)

(m2)

(c) minimum depth of the fairway

T

- draught

M

- margin (d)

n P f

(2.33)

(m)

H = T + M

of the typical vessel safety distance between the vessel bottcxn and the channel bottom (0.3 0.5 m)

-

minimum cross section, limited by the water level

- hydraulic c h a r a c t e r i s t i c of the waterway nP = F = 5-7 - cross section of the typical vessel

106 p

- number

r

-

of vessels coupled side-by-side

reduction coefficient: two-way stretch one-way stretch waterway tunnel

(e)

-

vIpaX

= 1 r = 0.6

r = 0.5

admissible velocity of the flow

vmax = F + A F -Qp A

r

(2.34)

.b . T

enlargement of the minimum cross section corresponding to the discharge Q

-

velocity of f l a w

'he design speed of vessels should be

w

=

0.55

-1

(2.35)

,

The velocity of flcw i s limited by the follawing equations v = 0.5

.w

but a l s o by

, i.e.

v = 0.275

.V-

(2.36)

I

v - vmx

The f l m velocity not only determines the speed when loaded (10 t o 400 km per day), but a l s o the operation capability and manoeuvrability of vessels and a r t i culated formations, as well as the necessary energy i n p u t and fuel consumption. The required speed of vessels i n relation to the channel cross section influences the backflow and thus the erosion rate. ( f ) routing of the fairway: The routing of the fairway including i t s extension i n curves determines the speed, fluency, safety, method of operation and the energy consumption of the inland water transport. The s t r a i g h t route is most suitable: two l i m i t s e x i s t for the value of the perimeter:

-

the minimim perimeter, securing fluent and safe operation without any significant restrictions,

-

the exceptionally acceptable perimeter, requiring limited speed and thus re-

ducing the fluency of operation (Tab. 2 . 7 ) . ?he exceptionally acceptable perimeter has to be used i n built-up areas, deep narrow valleys and natural river beds. Secondary characteristics of water courses which have an impact on the course and safety of transport operation, the operation t i m e and period , interruptions to operation, its r e s t r i c t i o n to some 220 to 340 days a year and the different technical measures employed include

-

flood occurrence

107

-

periods of low discharges i n non-canalized r i v e r s

- ice-bound regime

-

meteorological f a c t o r s , e s p e c i a l l y fog and s t r o n g wind occurrence maintenance, r e p a i r and r e c o n s t r u c t i o n work, e s p e c i a l l y i n the case of one-

way s t r e t c h e s - technologically u n s u i t a b l e and obsolete c o n s t r u c t i o n s , such a s locks and weirs. The f r e i g h t turnover of a waterway depends on the s t r e t c h with the lowest f r e i g h t c a p a c i t y , i . e . on the locks i n the case of double-way canals. The capac i t y of a one-way canal i s generally smller than t h a t of the lock. 'he f r e i g h t turnover of the lock can be expressed by the formula ( t per year) tn

-

duration of the operation cycle (lockage)

nd

-

n m b e r of v e s s e l s per day

d - duration of the t r a n s p o r t season

(2.37)

(hours)

(days)

m

-

number of simultaneously locked v e s s e l s

W

-

carrying capacity of one v e s s e l (medium)

(t)

a

-

c o e f f i c i e n t of capacity u t i l i z a t i o n

(0.7-0.9)

b

-

c o e f f i c i e n t of the uneven u t i l i z a t i o n of the waterway (1.25-1.75)

t

-

average number of operating hours per day

(12-24 h)

The volume of water needed f o r one lockage is

(m31

V l = F . h + W = s . d . h L W

(2.38)

and f o r the s l a n t walls of the lock

.

.d .h

W

V1

= ( 8 +

V1

-

b

- lock width

(m)

a

-

(d

2 h

tg6)

volume of water needed f o r one lockage

lock lenpth

h - head

-

slope of the lock walls

d

)

(m3)

(m) (O)

The plus s i g n before the value of the c a r r y i n g capacity is used f o r the

108 passage upstream, because water i n the lock has to be replaced a f t e r its departure from the lock. The minus s i g n i s used f o r the passage downstream. Idhen technical measures safeguard reciprocal lockage i n both d i r e c t i o n s , only 50%of the volume i s needed

v2

1

=

2 . v1

and, therefore f o r p r a c t i c a l cases (m3 1

V = k . a . b . h

-

k

c o e f f i c i e n t of operation coordination

( 1 k

(2.39) 0.5

1

The f r e i g h t t u r n w e r i n a complicated network of inland waterways has to be expressed by a more complex formula

/)2. d

K = a

2

ms

.

.

t

. ms . Ws .

(wm + wn)

+ 2 Pn

( P m - P n ) . tl

.

( t per year)

(2.40)

c o e f f i c i e n t of the uneven u t i l i z a t i o n of the waterway throughout the year

. b,’ - annual

average of the carrying capacity of simultaneously locked

vessels

wm

, wn -

Pm

3

pm

+

tl

t2

Pn

u t i l i z a t i o n of the carrying capacity i n e i t h e r d i r e c t i o n (%)

,

- percentage of vessels i n e i t h e r d i r e c t i o n

pn = loo%, pm

- pn>

0

-

duration of one lockage i f lockage i n the same d i r e c t i o n follows

-

(hours) ( = L e t i - t3 t6) i=l duration of one lockage i f lockage i n d i f f e r e n t d i r e c t i o n follows

-

(=

5

ti

-

Tab. 2.7)

1=1 Bearing t h i s i n mind, the annual water requirement f o r a lock is = 2

R

. Ka . m

a

S

( Pn.V2

. Ws .

+

/Pm+Pn/.V1

(wm+ wn)

1

(m3 per year)

(2.41)

The operation of locks is an inherently in-stream use, but using water i n t h i s way r e s u l t s i n a loss of i t s p o t e n t i a l energy both i n the passage upstream and i n the passage downstream: J U = h . ( a . b . h + W ) . C J d = h . ( a . b . h - W ) . F Ju

- loss

of potential energy i n the passage upstream

109 Jd - loss of p o t e n t i a l energy i n the passage downstream

(kg .m-3)

b” - u n i t mass of water

R e passage upstream decreases the energy consimp t i o n ( i .e. a l s o f u e l consumption), the reverse operation of locks f o r the passage downstream has no e f f e c t on f u e l consumption. TABLE 2.7

Symbol

Duration

Opera t i o n

drift in d r i f t out tl(5) =

t5

+ (5-10).% r

(m. s-l)

see formula

r =0.6-1 1 r =0.8-2.2

t2

opening and c l o s i n g the upper g a t e

6C-120

t4

opening and c l o s i n g the lower gate

60-120

f i l l i n g the lock

t3 t6

emptying the lock t3(6) =

h

7

Velocity

(S)

5

300-900 ~0.02-0.06

Duration of one operation cycle of a navigation lock with two-way t r a f f i c . Symbols a r e i n t e x t . The water requirements f o r inland navigation a r e determined by the s i z e of the l a r g e s t l o c k , i . e . i n the case of u n i f i e d h o r i z o n t a l dimensions by the volume o f the lock with the h i g h e s t head i n c l . r e l e v a n t water l o s s e s . These water requirements can be reduced by (a)

two grouped locks

(b)

wa ter-saving tanks

Cc) pumping (d) v e s s e l l i f t s , canal i n c l i n e s , water slopes. The f i r s t two technical measures reduce the water requirements and simultaneously i n c r e a s e the duration of lockage. Pumping and mechanicel l i f t i n g equipment can shorten t h i s operation, b u t , unless a counterweight is used, t h i s is

.

energy-demanding By grouping two locks, i.e. by emptying one lock i n t o another, water requirements can be reduced by 50%. During r o u t i n e operation of grouped locks, the duration of t h e lockage is shortened by c l o s i n g the valve before equalizing the water l e v e l s , thus i n c r e a s i n g the water requirements t o the average value Ra = 0,53

k

-

.k .a .b .h

c o e f f i c i e n t of the operation coordination

(2.43) (1 > k > 0.5)

110 The e f f e c t of water-saving tanks on reducing water requirements depends on their s i z e , number and technical arrangement (Tab. 2.8). The water requirements of a lock with water-savinp tanks of the same s i z e R

S

=

(2.44)

n - nunbes of water-saving tanks

x =

9 - r a t i o of the s i z e of

Y

hn --

=

the lock to the s i z e of the tank

r a t i o of the water s t r a t a hn for particular tanks and of the difference of water tables ho reached a t the moment of the cmencement of f i l l i n g up fran the next tank for time-saving reasons

ho

TABLE 2.8

Number of reservoirs

Full levelling of water tables (y = 00 ) requirements

v,

:

\lo

P a r t i a l levelling of water tables (y = 1 0 )

Ratio of duration

requirements

tS : to

:

vs

vo

duration ts : to

0.687

1.145

1.414

0.523

1.276

1.581

0.423

1.395

0.355

1.505

1

0.666

1.225

2 3

0.5 0.4

4

0.333

1.732

Decrease i n water requirements and the extension i n duration of one operation cycle of a navigation lock with watersaving reservoirs, their area being equal to that of the lock. The following formula can be derived for the duration of the f i l l i n g up of the lock with wa ter-saving tanks

1

n

br;

-4+ y q Chrs )

to

- duration

(2.45)

of the f i l l i n g up of the lock without watersaving tanks (hrs)

Water requirements for lockage r e s t r i c t other in-stream uses, e.g. for hydropmer generation, and should only be considered when the natural supply by river discharges is not s u f f i c i e n t . Water losses of navigation operation are caused by (a)

leakage of gates and valves

(b)

seepage of the bottom and the banks of the canal

(c) evaporation from the free water surface and the increased evapotranspiration from banks affected by the impounded water.

111 'Ihe losses through the leakage of gates and valves depend on t h e i r construction, type of s e a l and technological s t a t e as well as on the lockage frequency. Their value fluctuates between 3 and 5 1.s-I f o r 1 m of head f o r locks 12 m wide. Higher values correspond to a higher frequency of lockage. Inland water transport does not make any important requirements on water quality, except recreational passenger transport, whose success i s closely interconnected with the quality of water. Water pollution fran inland navigation is mainly caused by the liquid fuels used i n vessels, chemical products incl. hydrocarbons and other dangerous substances transported as cargo, s o l i d wastes , degassing, washing and b a l l a s t water, but especially by accidental spillage d u r ing loading, unloading and transloading.

2.3.3

\dater Pmer Utilization

The potential energy of water can be converted i n t o pressure energy by concentrating the head and discharge and i n t o k i n e t i c energy by passing the concentrated discharge through water engines. Zhe value of the e l e c t r i c energy generated from this k i n e t i c energy reaches (2.46) Q

-

discharge

<m3.s-l)

H

-

net head (without intake losses)

(m)

i~ N

-

coefficient of efficiency (turbine, gears, generator)

.

u n i t mass of water

(kg m-3 )

power generated

(kw)

To e x t r a c t the maximum power and energy a t the optimum cost the design crit e r i a focus on the choice of the location, design discharge and head, lay-out, s i z e and number of units e t c . by suitable numerical techniques. This approach embodies an optimization of the power output/cost-benefit r a t i o e t c . on the

basis of a r e a l i s t i c operation of the plant, i n the framework of the topographic/ hydrological s i t u a t i o n and power market demands. The specific advantages of hydropower plants open up favourable p o s s i b i l i t i e s of application as

-

run-of-river

plants ( i n the original r i v e r bed o r i n a bypass canal, using

discharges which a r e available without considerable storage),

-

storage plants (using reservoirs f o r water accunulation and thus affording

the p o s s i b i l i t y of peak pmer generation)

-

pumped-storage plants (repumping accunulated water during a surplus of energy

i n the network and generating power during peak demand)

112 -

tidal power p l a n t s ( u t i l i z i n g the head and flow produced by the t i d e )

-

power s t a t i o n s using the energy of waves ( n o t f e a s i b l e y e t ) .

NATIONAL ECONOMIC, ENVIRONMENTAL AND SOCIAL POLICES

ENERGY DEMAND ANALYSIS AND FORECAST

ENERGY SURVEY

I EXISTING POWER SYSTEMS

POTENTIAL

Project catalog coal, gas,oil. nuclear,

PROJECTS

hydro, non-conventional

PROJECT SELECTION OPTIMIZATION OF POWER GENE RAT ION AND TRANSITION SYSTEM EXPANSION

Criteria

I Cover the growing energy demand 2 Minimize energy cost 3 Minimize investment cost 4 Maximize exploitation of the discharge and head available Security of the energy supply Local development Conservation of res-ources Protection of the environment Secondary benefits

5 6 7 8 9

I PRICING

ECONOMIC

POLICY

EVALUATION

Criteria Net present worth NPW Economic r a t s of return ERR Criteria. Capital available

RECOMMENDED POWER DEVELOPMENT PROGRAMMES TIMING

Fig. 2.5. Block diagram f o r the p r o j e c t s e l e c t i o n , optimization of power generat i o n and t r a n s i t i o n system expansion i n the framework of n a t i o n a l economic, environmental and s o c i a l p o l i c i e s . Hydropower i s the only dependable renewable source of energy and o f f e r s , i n a d d i t i o n i n comparison with thermal and nuclear power, a s w e l l a s with the unconventional energy o p t i o n s , the following b a s i c advantages : -

f l e x i b i l i t y of operation,

-

p o s s i b i l i t y of multipurpose u t i l i z a t i o n , high r e l i a b i l i t y and long s e r v i c e l i f e , p o s i t i v e o r almost n e g l i g i b l e environmental impact ( i f environmental f a c t o r s

a r e accordingly taken i n t o account during the design and o p e r a t i o n ) ,

-

low operating c o s t s , p o s s i b i l i t i e s of using l o c a l m a t e r i a l s and labour. The following i n d i c a t o r s a f f e c t i n g the choice of the optimum design discharge

113 and head have to be considered with a p o s s i b l e environmental h p a c t of the p m e r p l a n t layout: - u n i t c o s t of energy (kwh) should be competitive with o t h e r energy options,

-

i n s t a l l e d capacity (kwh) should be optimum f o r i n t e g r a t i o n i n t o the network

power market, - energy output i n the period o r season of maximum energy demand (kwh) should be optimum. Available simulation models have the c a p a b i l i t y of simulating any hydropower p l a n t o r e l e c t r i c a l system, Computations m y be performed a t a desired l e v e l of accuracy c o n s i s t e n t with the a v a i l a b i l i t y of the input d a t a . These programs may be used t o determine hydropower p o t e n t i a l , t o optimize design discharges, heads, d a m heights and r e s e r v o i r s i z e s , t o study the f e a s i b i l i t y of new developments

and t h e i r impact on e x i s t i n g systems, e f f e c t s of changes i n operational procedures i n e x i s t i n g systems e t c . (Fig. 2.5). MW

\ \

0

0 2

INCREMENTAL COST BENEFIT

-

0.4

06

08

10

Fig. 2.6. S e l e c t i o n of the optimum capacity of a hydropower p l a n t by superimposing the incremental cos t-benefit r a t i o function on t h e power duration curve according to Fahlbusch (1983). According t o Fahlbusch (1983) the optimum capacity of a hydropower p l a n t , i f the o b j e c t i v e i s the maximum e x p l o i t a t i o n of energy and n o t the provision of peak c a p a c i t y , is t h a t value of t h e o r e t i c a l capacity N f o r which the complemen-

tary emulative d i s t r i b u t i o n of power output equals t h e marginal benefit-cost ratio

(2.47) +f(x)dx =

C ") M. to

(2.48)

Solving t h i s equation f o r the optimum N requires superimposing the margiOP t ~l cost-benefit r a t i o function on the power duration curve (Fig. 2.6).

114

x

-

power output

f(x)

-

p r o b a b i l i t y d e n s i t y of power output x

C(N)

-

annual c o s t a s a function of capacity

- value of to - duration

M

energy per kwh of one year i n hours (8760 h r s )

AC

-

AB

- incremental

incremental c o s t s benefits

A hydropower development p r o j e c t may e x h i b i t an incremental cos t-benefit

r a t i o of less than u n i t y and s t i l l be uneconomical, r e q u i r i n g s u b s t a n t i a l investment f o r the construction of s t o r a g e and diversion f a c i l i t i e s , which may be l a r g e l y independent of the design capacity. The trouble-free and economic operation of power p l a n t s requires a low cont e n t of sediments (both bed load and suspended matter, e s p e c i a l l y hard minerals), a low content of f l o a t i n g d e b r i s and chemically non-aggressive water q u a l i t y , which means t h a t a low content of oxygen, low chemical a g g r e s s i v i t y and a low temperature i s required i n order t o r e s t r i c t : (a) (b)

c a v i t a t i o n and chemical d i s i n t e g r a t i o n of t u r b i n e s , abrasion of pressure p i p e l i n e s , s p i r a l c a s e , t u r b i n e s , l i n e r and o t h e r

technological equipment, ( c ) sedimentation i n water conveyance s t r u c t u r e s . The t r a n s p o r t of bed-load and suspended matter r e q u i r e s the construction of s p e c i a l i n t a k e s t r u c t u r e s and s i l t basins. I t a l s o requires a minimum flow r a t e of some 1 . 0 m.s-',

dependent on the c h a r a c t e r i s t i c s of the p r e v a i l i n g p a r t i c l e s ,

i n order t o avoid sedimentation i n the conduit system. The design dimensions of these s t r u c t u r e s should be determined i n t h e light of the s i z e and density of the p a r t i c l e s and t h e i r volume which can be allcwed t o e n t e r the system. No o p e r a t i o n a l troubles caused by sediment t r a n s p o r t occur i n s t o r a g e p l a n t s with a r e s e r v o i r which has a s u f f i c i e n t t r a p e f f i c i e n c y . Run-of-river

plants

cope with s e r i o u s sediment problem when t h e design discharge Qi exceeds the crit i c a l discharge Qs a t which the bed load starts t o move:

Q;

< 4,

(m3.s-l)

(2.49)

I n rivers with a heavy bed load t r a n s p o r t i t is useful t o l o c a t e t h e off-take i n an eroded s e c t i o n . I f the off-take i s located i n a s e c t i o n where sedimentation p r e v a i l s , i t is necessary t o narrow t h e r i v e r bed i n t h i s p a r t i c u l a r s e c t i o n . The bed load t r a n s p o r t normally needs the energy of some 50% of the discharge. To avoid sediment t r a n s p o r t problgns during a period of increased bed load trans-

li5 port (Qa

>

Q,),

the hydropower s t a t i o n may u t i l i z e some 50% of the discharges

available Qe =

1

7 . Qa

(m3. s-l)

(2.50)

even when t h e i n t a k e i s w e l l l o c a t e d . p l a n t i n a river with a heavy bed load The operation of a run-of-river t r a n s p o r t and f l u c t u a t i n g discharges i s , t h e r e f o r e , limited i n two time periods because of the lack of water during a period with a c t u a l discharpes Qa lower

-

<

than the design discharge Qi (Qa Q i ) f o r the t r a n s p o r t of sediments i n the period when the a c t u a l discharges Qa

-

exceed the c r i t i c a l discharge Q,,

but do n o t reach the double of t h i s value

<

(Qs < Qa 2Qs). No l i m i t a t i o n of such p l a n t operation i s required during high discharges (Qa => 2Qs). Rut, under these conditions, the power generation is r e s t r i c t e d by the decrease i n head a v a i l a b l e :

(2.51)

2.3.4

Water f o r Recreation

Recreation includes a l l a c t i v i t i e s whose s o c i a l goal is t o gain o r recover physical and psychic f o r c e s . Water r e c r e a t i o n does n o t only include bathing, swiming, f i s h i n g and o t h e r water s p o r t s , but a l s o boating, yachting, some winter s p o r t s l i k e s k a t i n g e t c . , and sojourns beside the water such a s camping,

caravanning and o t h e r forms of short-term or weekend sojourn. Areas r i c h i n s u r f a c e water s u b s t a n t i a l l y ameliorate the r e c r e a t i o n condit i o n s i n a r i d , semiarid and humid climates, b u t do not have such a p o s i t i v e impact under conditions of rough climate. Water r e c r e a t i o n may be c l a s s i f i e d as (Tab. 2.9, 2.10): ( a ) everyday - r e s e r v o i r s and a c c e s s i b l e water courses, swiming pools i n the proximity of dwelling a r e a s (up t o 20 km), (b) weekend - r e s e r v o i r s and water courses whose d i s t a n c e from r e l e v a n t dwelling a r e a s exceeds 20 km (up t o 200 km)

( c ) seasonal - a r e a s of r e c r e a t i o n a l c h a r a c t e r whose d i s t a n c e from relevant dwelling a r e a s exceeds 200 km. The q u a l i t y of water r e c r e a t i o n depends on (a)

water mnagement f a c t o r s ,

(b)

climatological f a c t o r s ,

(c)

l o c a l f a c t o r s i n c l . topographical and a e s t h e t i c f a c t o r s .

The pre-condition

f o r the r e c r e a t i o n a l e f f e c t of a given a r e a is the change

of m i l i e u : R e l a t i v e l y warm a r e a s a r e p e r t i n e n t for r e c r e a t i o n i n a mild climate,

116 r e l a t i v e l y cool a r e a s i n a s e m i a r i d and a r i d climate TABLE 2.9

Type of recreation

Deciding factors

5 P e of recreation

Deciding factors

~~

1 bathing

151-6 & 8 K1-4, M1-6

7 yachting

2 water tourism 3 rowing ii paddling 4 fishing

Wl-3 6 5 , K1-2, M5-6

motorboating 8 recreational sb Y 9 skating

141, 3-5, K4, M6

W1, 4-7, M4

1573-5, M3 W 1 , K1, M3

W6, 4 , M3

Categorization of water r e c r e a t i o n ( b a s i c c h a r a c t e r i s t i c s of deciding f a c t o r s see t a b l e 2.13). Water q u a l i t y i n c l . temperature i s t h e most important f a c t o r which influences the q u a l i t y of r e c r e a t i o n i n r e l a t i o n t o the type of r e c r e a t i o n a c t i v i t y (Tab. 2.10). Bathing and swiming is a supplementary a c t i v i t y f o r o t h e r r e c r e a t i o n a c t i v i t i e s , d i s t i n g u i s h e d by the h i g h e s t requirements on most f a c t o r s . Water temperature is n o t n e c e s s a r i l y connected with clim t o l o g i c a l f a c t o r s . Thermal waters may c r e a t e extremely favourable conditions for r e c r e a t i o n , e s p e c i a l l y i n less favourable c l i m a t i c conditions. Under such conditions the influence of climatological f a c t o r s may appear of t e r t i a r y importance. TABLE 2.11

Category of visitors Children Non-swimmers Swimmers Ida ter jumping

Required water depth (m)

0 - 0.8 0.8 - 1 . 3 > 1.3 3.4 - 5

I d e a l s h a r e of t h e water t a b l e area (%) 20%

40% 40% min 16.25.14 m

Required water depth and t h e i d e a l share of t h e water t a b l e area f o r r e l e v a n t c a t e g o r i e s of v i s i t o r s t o n a t u r a l and a r t i f i c i a l bathing pools. The q u a l i t y of n a t u r a l bathing pools depends on the morphological and aesthet i c conditions of the environment and on a favourable water depth f o r s w h e r s , non-swimmers, c h i l d r e n and d i v e r s (Tab. 2.11, 2.12). The a c t i v e a r e a on b i g r e s e r v o i r s i s a zone near the s h o r e , some 50 m wide. The s i z e of bathing and swinnning pools should correspond t o the length of race t r a c k s , which a r e r a t i o s of 50 m: 10 m, 12.5 m, 16.67 m and 25 m. I n a swimming pool of 50.21 m, a s recornended by FINA with a water depth above 1 . 8 m,

TABLE 2.10

1. Water p o l l u t i o n (class) 2. Water temperature

Ia

Ib

11

>25

> 18

> 14

(14

> 1.6

<0.5

111 1. Number of high sumner days

>

2. R a i n f a l l t o t a l i n s m e r (m)

(250 <450 ,600

70 >50 <50 1. Riverbed mat e r i a 1

sand

mud

OC

3 . Water depth

(m)

4 . Water t a b l e width (m) 5. Velocity of f l o w (m.s-1) 6. Water t a b l e f l u c t u a t i o n (m)

7 . F i s h occurrence 8. Variance with o t h e r water management purposes

0.5 (1.6 -1.6 >20 >10 <0.5

(0.5

0.5 -1.1 .< 2

plentiful no

> 5 <5 v1.5 >1.5

> 2 >> scarce

partially

2

3. A i r temperature OC (% humidity)

nil

4. Air pollution

yes

5. Moise

Categories of parameters which determine q u a l i t y of r e c r e a t i o n .

21-26 (18-70) no

no

<

2. Bank slope

18 3 . A c c e s s i b i l i t y

yes

4. Insect

<1:3.3 > 1 : 2

good

difficult

no

yes

occurrence

5. Aesthetic of no s l i g h t yes

pleathe environment s a n t 6. Services (for good mass recreation)

uninteresting poor

118 i t is possible t o play water polo. TABLE 2.12 Limiting value (maximtun or minimum)

Parame t e r

m 200 m2 < 0.5 m.s-' 0.3 rn.s-l 1 m3 <30 %

Water table width Minimun area of the water table Velocity of flow - for adults

>10

- f o r children

Minimum discharge per v i s i t o r and day Rottom slope Bottom material Water temperature Class of water quality

sand, pebble, pavement, concrete > 18 OC I (max 11)

Area of water table per v i s i t o r

> 2.5 m2

Total surface area per v i s i t o r

>10 m 2

Lj-miting values of basic parameters t o ensure mod conditions for recreating a t natural bathing pools. The o p t i m flow r a t e and fluctuation of the water table not only depend on the type of recreation, but a l s o on the morphology of the terrain: on the material of the bottom, on the slope and accessibility of the banks. An optimum velocity of flow for mst a c t i v i t i e s i s below 0.5 m . s - l . The permissible fluctuation of the water table also determines the water q u a l i t y (Tab. 2.13). The physical need to bathe appears when the daily temperature exceeds 25OC. A reservoir offers Emd conditions for bathing whenever the number of such days

is higher than 50-70 annually and precipitation i n t h i s period does not exceed 450 mm. Conditions a r e favourable for a recreational stay near water when the average daily temperature i s above 10°C, i . e . from April to October i n a mild clima te. Last but not l e a s t , the quality of water recreation depends on the quality of the a i r , the noise and the occurrence of insects. The morphology may create a favourable climate i n a natural milieu or i n a housing e s t a t e . The climatic pleasantness depends on the relation of the amount of diffused and reflected s o l a r radiation, which influences the a i r temperature and humidity (Fig. 2.7). To m i n t a i n t h e water quality i n swimning and bathing pools, an exchange of water is required, which may be (a) continuous, (b) inmediate, (c) achieved by the circulation of water.

119 TABLE 2.13

Bathing pool

Water quality indicators

na tura 1

artificial

Physical properties : Temperature minimum

14

OC

14

OC

optimum

21

OC

21

OC

Visibility i n water Turbidity (Si02- content)

>0.5 m

> 5 m

-

depth down to l m

-

depth down to 2m

-

> 2 mg.1-1 > 1 mg. 1-l

Chemical properties Factor pH Organic matter Chloride

- 9.0 -

5.5

100 mg.1-l

1 mg. 1-l

h n i a Nitrides Nitrates

6.8 i + i + i + i + i +

- 7.1 30 mg.1-I 0.3 mg.1-I 0.3 mg.1-I 0.2 mg.1-l 20 mg.1-l

Water quality indicators f o r natural and a r t i f i c i a l bathing pools. i quality indicator of the inflow.

- water

relative humidity

Fig. 2.7. Relation of temperature and r e l a t i v e hunidity t o attaining favourable feeling during water recreation i n a mild clin-ate. Sunshine and wind motion appear a s important secondary factors: 1 lack of a i r motion, 2 - lack of shadow.

-

120 Water q u a l i t y standards f o r indoor and outdoor swimming pools approach the requirements f o r drinking water (Tab. 2 . 1 4 ) . The r e l e v a n t q u a n t i t a t i v e requirements include ( a ) f i l l i n g water R f

-

i t s volume corresponds t o the volume of the pool and

of the r e l e v a n t i n s t a l l a t i o n s f o r water c i r c u l a t i o n etc. R f = V . (b) supplementary water Rs - compensating losses through s p i l l i n g , seepage, leakage, evapora t i o n etc. ( c ) d i l u t i o n water Rd - t o ensure the required concentration of p o l l u t i n g substances, concentrated by the operation of the pool. The q u a n t i t y of d i l u t i o n water f o r pools without water c i r c u l a t i o n can be derived from the permissible increment i n the content of c h l o r i d e s , measured t o the permissible value of c h l o r i d e s i n the water resource. The s p e c i f i c d a i l y p o l l u t i o n increment is

2 g per c a p i t a and day f o r outdoor afid indoor s w i m i n g pools 1 g per c a p i t a and day f o r n a t u r a l bathing pools, t h e r e f o r e =

Rd =

Rd

- water

66 1 per capita and day.

requirements of d i l u t i o n water f o r outdoor s w h i n g pools.

During water c i r c u l a t i o n a 0.25 m l a y e r of water has t o be replaced i n the course of one hour. The required capacity of the water treatment p l a n t has to be (m3 .s-'>

(2.52)

Rc - r e c y c l e d discharge A

- a r e a of t h e swimming pool

(mL)

Idhen water is being c i r c u l a t e d i n a n a t u r a l bathing pool, the recomnended 3 design discharge for t h e treatment p l a n t is 0.5 m per c a p i t a and day. Large %hrming pools r e q u i r e a continuous process of c i r c u l a t i o n ; an i n t e r r u p t e d process is r e c m e n d e d f o r srrall pools with only a 4 hour cycle.

As a w a t e r s a v i n g technique and i n o r d e r t o improve the water q u a l i t y , the c i r c u l a t e d water can be used f o r showers, flushing, f i l t e r washing and the cleaning of t h e r e c r e a t i o n a l amenities.

2.4

MUNICIPAL AND RURAL IdAER REQIJIREMEITE

The amount and q u a l i t y of water used i n human settlernents influences the soc i a l development of t h e s o c i e t y concerned and a f f e c t s t h e b i o l o g i c a l development of the i n d i v i d u a l human beings. The q u a l i t y and q u a n t i t y of drinking water supp-

121

l i e d t o organisms has a d i r e c t e f f e c t on h e a l t h . Water s u p p l i e s important minerals t o organisms. The long-term u t i l i z a t i o n of the same water f o r d r i n k i n g and cooking purposes by a n i n d i v i d u a l influences the development of the organism and i t s h e r e d i t a r y s i g n s . The amount and q u a l i t y of water used f o r washing and bathing has a considerable influence on h e a l t h conditions i n human s e t t l e m e n t s . The e x t e n t of these influences depends on the physiological a d a p t a b i l i t y and c h a r a c t e r i s t i c p r o p e r t i e s of m n i n t h e framework of the homeostasis of h i s own b i o l o g i c a l system, on the energy input and output of r e l e v a n t i n d i v i d u a l s , on the supply of nutriments, vitamins and on o t h e r s a n i t a r y conditions. The mode and frequency of t h e r e l e v a n t organism's c o n t a c t with water is a f u r t h e r important f a c t o r . Water demand i n households, workshops and public s e r vices has d i f f e r e n t q u a l i t y requirements f o r : ( a ) drinking (and o t h e r uses r e s u l t i n g i n i n t e r n a l c o n t a c t of water with the human body : mea 1 preparation) , (b) o t h e r domestic uses i n c o n t a c t with the s u r f a c e of the human body physical care : washing, showering, bathing d i s h washing laundry ( c ) using water i n systems where c o n t a c t with the body can be avoided

laundry house cleaning and c a r washing yard and park watering, street cleaning, sewer f l u s h i n g t o i l e t rinsing f i r e extinguishing (d) using water i n closed systems heating a i r conditioning. The supply of water of uniform q u a l i t y f o r each of these technologically d i f f e r e n t purposes is the simplest method t o safeguard a l l these requirements by means of one supply network. I n p r a c t i c a l cases t h i s method m y not appear

a s the most economic o r s u i t a b l e t o p o s i t i v e l y influence the development of human organisms and t h e i r h e a l t h .

2.4.1 Water Requirements f o r Drinking and Cookirg Purposes The physiological water requirements of a healthy i n d i v i d w l reaches a n average of 1.5 t o 15 liters p e r day. The metabolic processes of each individual tend to achieve a balanced s t a g e , depending on c l i m a t o l o g i c a l conditions personal weight and i n d i v i d u a l a c t i v i t i e s (profession, hobbies) and customs (drinking, e a t i n g , dressing) thus r e q u i r i n g a s t a b l e complementing o f water l o s s e s . The physiological water requirement of some 2.5 1 per c a p i t a and day is co-

122 vered 50%by food and 50% by beverages. I n addition t o t h i s , a healthy organism produces some 0.3 1 of metabolic water per day by processing the basic nutriments. The physiological water requirements per capita and day Ri can, therefore, be expressed by the following equation Ri = f (w, a , c , h , f , m)

- Rf

( 1 per capita and day)

(2.53)

w

-

individual weight

a

-

a c t i v i t i e s (profession, hobbies, age)

c

-

climate (especially temperature and humidity)

h

- personal habits (quality and quantity of dripking, dressing e t c . )

f

- food canposition

m

-

metabolic function (less important)

Rf

-

content of water i n food.

The hman organism is influenced by the amunt and quality of accepted water,

especially i f ancestors have been living i n the same place f o r generations. The anorganic and organic constituents of water have a d i r e c t influence on the hmlan organism, i.e. physiologically, and an indirect influence, i . e . psychically, both positively and negatively. The human organism generally, depending on i t s individual properties, may get accustomed t o the influence of natural water cons t i t u e n t s and their canbination, o r may produce relevant a n t i m a t t e r . But some constituents of water, especially those corning from pollution through wastes f r m industry and agriculture, m y cause diseases o r morbid changes, namely (a)

teratogenic (may induce morbid changes of the organism)

(b)

mutagenous matter (may produce hereditary changes)

(c) cancerogenous matter (may cause m l i g n a n t t m u r s ) . These matter and t h e i r function a r e not sufficiently known, because the reaction of any organism to such matter depends t o a considerable extent on t h e i r quantity, canbination and concentration, a s well as on the organism's health and habits. The degree of resistance depends on the health standard, hereditary and personal resistance o r disposition and age of the individual concerned. Occasional drinking of unsuitable water may not be dangerous when the relevant harmful concentrations a r e law and when the relevant organisms does not contain potentially dangerous germs. The organism's own bacteria l i m i t the development of the accepted bacteria. On the contrary, daily drinking of physiologically o r sensorially unsuitable though s a n i t a r i l y non-defective water which only corresponds t o basic standardized indicators may cause unexpected comequences

.

To achieve the healthy developmmt of the population, i t is e s s e n t i a l to

123 secure an everyday supply of physiologically b e n e f i c i a l and s e n s o r i a l l y aggreea b l e water, a t l e a s t f o r drinking purposes. I f the q u a l i t y of water i n the pipel i n e system does not correspond t o these c r i t e r i a , i t is v i t a l to supply b o t t l e d water of physiologically b e n e f i c i a l q u a l i t y , a t l e a s t f o r sucklings. For t h i s reason, i t is a l s o a d v i s a b l e t o organise t h e production of a l l beverages using, without exception, groundwater resources of the b e s t q u a l i t y a v a i l a b l e . The standards f o r water q u a l i t y should be derived from the mode of contact of hurnan organism with water, because t h i s is

-

( a ) r e g u l a r l y absorbed by the organism, without b o i l i n g a f t e r boiling, o r (b) i n temporary c o n t a c t with the whole s u r f a c e of the organism (and m y be

a c c i d e n t a l l y swallowed during showering, swimming e t c . ) ( c ) i n r e s t r i c t e d i n c i d e n t a l s u r f a c e c o n t a c t with a p a r t of the body (during washing, cleaning, s p r i n k l i n g e t c . ) (d) used i n closed systems, excluding c o n t a c t with the organism ( a i r cond i t i o n i n g , h e a t i n g , t o i l e t r i n s i n g , d r i p and subsurface i r r i g a t i o n ) . I n only one supply system is used f o r a l l the purposes of municipal o r r u r a l water supply, a s is u s u a l , the water q u a l i t y should correspond to the h i g h e s t q u a l i t y requirements, i . e . to drinking water requirements. I f such water is not I

a v a i l a b l e f o r a l l required purposes, s a n i t a r i l y non-defective water should be used f o r such purposes, where c o n t a c t with the organism cannot technically be excluded. The supply of the necessary amount of such water, whose value depends on l o c a l conditions , prevents the occurrence of w a t e r b o r n e diseases. The l e v e l of knowledge about t h e b i o l o g i c a l importance of the d i f f e r e n t elements and components p r e s e n t i n water and t h e i r canbination i s generally low, except the a p p r e c i a t i o n of the medical e f f e c t of some mineral waters. Not even the e f f e c t of such b a s i c components a s calcium Ca o r magnesium Mg has been s u f f i c i e n t l y i n v e s t i g a t e d . The knowledge on the e f f e c t of t r a c e elements and e s p e c i a l l y o f the s y n e r g e t i c o r anta,gonistic e f f e c t s of t h e i r combinations: iodin J and f l u o r i n e F, f l u o r i n e F and molybden Mb e t c . , is a l s o low. The r e a c t i o n of the organism t o the impact of these elements can have considerable individual o r h e r e d i t a r y e f f e c t s , a l s o i n canbination with o t h e r e x t e r

nal f a c t o r s such a s climate, overloading of the organism, the organism’s stage of developnent, h e a l t h state e t c . Water of a d i f f e r e n t q u a l i t y can be used f o r d i f f e r e n t purposes of domestic use and relevant q u a l i t y i n d i c a t o r s f o r any cate-

gory of i t s p a r t i c u l a r use can be derived frcm the (a)

s a n i t a r y non-defectiveness,

(b)

physiological b e n e f i t ,

(c)

s e n s o r i a l agreeableness (Fig. 2.8).

124

. toilet rinsing sprinkling

washing, bathing cleaning, laundry

meal preporation,

drinking

cooking

Fig. 2.8. Hierarchy of goals and requirements on water quality f o r municipal water supply and p o s s i b i l i t i e s of water delivering water of d i f f e r e n t quality f o r relevant purposes. The physiological benefit f r m water depends not only on i t s chemical and bacteriological canposition, but a l s o on its temperature, flavour and odour a s the cmponents of i t s sensorial properties. The q u a l i t y of water i n the supply network depends on the quality of raw water and can be defined by means of standards. The i n t e r s t a t e coordination of these values i s organized under the auspices of the World Health Organization and the International Standard Organization. The health and optimum development of the population can be permanently and e f f e c t i v e l y influenced through the u t i l i z a t i o n of appropriate water resources and through sophisticated water treatment (Tab. 2.14, 2.15, 2.16). Water q u a l i t y can be defined and standardized by means of indicators expressing the limiting concentrations of relevant components and other water proper-

ties with regard t o t h e i r health e f f e c t . Their values have t o be derived from the character and intensity of impact of the relevant canponents of the human organism. The number, type, methods and frequency of sampling and analytic methods a r e a l s o standardized. The relevant values can be standardized a s (a) maximum permissible values - water which exceeds these values may not be considered a s drinking water (mandatory l i m i t s ) , (b) reccmnended l i m i t s - the r a t e of t h e i r occasional o r permanent excess has to be analyzed individually i n consideration of local conditions (and o f f i c i a l l y approved). Relevant drinking- water quality requirements may d i f f e r f o r temporary o r in-

125 TABLE 2.14

Selected i n d i c a t o r s

Physical: - colour

'Pt

300

According t o the p l a tinurncobalt scale

Chemical : a ) matter influencing s u i t a b i l i t y f o r drinking: Total evaporation residium Iron (Fe) t o t a l Manganese )In Cu Copper Zinc Zn @SO4 + Na2S04 Sodium alkylbenzenesulphona t e b) matter a f f e c t i n g h e a l t h : N i t r a t e s NO;

Fluor F- d e r i v a t i v e s

c ) toxic matter : Phenol d e r i v a t i v e s Arsenic As Cadmium Cd Chromium Cr-6 Cyanids CNLead Pb Selenum Se Total -activity d) matter i n d i c a t i n g p o l l u t i o n : Oxidability Biochemical oxygen demand BOD5 Nitrogen N ( t o t a l ) h m n i a NH3 E x t r a c t a b l e m t t e r CCE Fat

1000 50 5 1.5 1.5 1000 0.5 45

Higher content when the anmonia content is below 0 . 5 mg.1-1, due t o the corrosion e f f e c t

1.5

G u s ing me tahenioglobinanemia i n s e n s i t i v e individuals i n concentration 100 rng.1-1. Higher concentration causes f l u o r o s i s , concent r a t i o n 0.8.-1.0 mg. 1-1 a r e a n t i c a r e t i c prevention.

0.002 0.05 0.01 0.05 0.20

gas works, chemical industry, volcanic waste from metal coating

0.05 0.01 1000 c.1-1

10.0 6.0 1.0 0.5 0.5 1. 0

Maximum peimissible content of chemicals i n raw water t h a t m y be t r e a t e d f o r drinking purposes, according t o the recomnenda t i o n of t h e World Health Organization. d i v i d u 1 water supply and for p e m n e n t c o l l e c t i v e municipal and r u r a l supply, where mre s t r i c t c r i t e r i a have t o be applied with regard t o possible i n f e c t i o n , epidemics e t c . From the metodological p o i n t of view i t is possible to d i s t i n guish such i n d i c a t o r s a s

126 TABLE 2.15 Class

Bacteriological pollution

Bacteria c o l i per 100 m l

Required treatment

I.

slight

0

-

50

11.

medium

50-

5000

current processes : coagulation, filtration

50000

special treatment water has t o be used i f inevitable only

111.

IV.

high excessive

500

-

>50000

disinfection only

Classification of raw water used f o r drinking purposes a f t e r i t s bacteriological pollution according t o the recomnendation of the World Health Organization. TABLE 2.16

Water course Chloride (CL-) Sulphide (SO); Calcium (Ca) Magnesium (Mg) Fluoride (F)

400 300 300

200

Raw water

Drinking water recom. max.

200 200 250 125

20 60 36 30 1.0 0 20

2.4

1.5

Ammonia (W3)

3

0.5

Nitrate (NO;) Nitride (NO;) Sulfate (SO$-)

50

-

25

-

-

30 70

60 1.3

0.2 30

0.01

0.05 50.0 0.02

1.5

0.5

0.05

0.1

Manganese (Mn) Cyanide (CN)

0.5 0.2

0.2 0.01

0.01

0.03

0.01

0.05

Zinc (zn) Nickel (Ni) Lead (Pb) Chromium (Cr) Arsenic (As)

2 0.1 0.1 0.1 0.5 0.2 0.1

2

1

2

fiospha t e (PO:-) Iron (Fe- t o t a l )

Copper (CU) Selenium (se) Mercury (Hg) Cadmium (b) Alluminiun (Al) Free Chlorine (c1) W g e n (02) (min 5.0)

25.0

0.05

0

0.04

0

0.04

0.05

0.05 0.04 0 0.003 0.0001 0

0.05 0.01

0.04 0.05 0.05

0.005

0.001

0.3

0.005

0.004 0.005 0.05

0.1

0.3

8.0

10.0

Selected admissible values of ion content (mg.1-I> i n water courses; surface Water used for municipal water supply and i n drinking water (recmended and maximum admissible values),

127 (a)

bacteriological and biological icdicators

(b)

chemical and physical indicators.

Drinking water may be defined as s a n i t a r i l y non-defective water when i t does not cause any health troubles o r diseases, even a f t e r lorg-term u t i l i z a t i o n . I n addition, water delivered f o r municipal and domestic purposes should be wholesome and palatable. Water from underground sources i s preferred t o surfacewater delivery. Groundwater contains more bioelements important t o human organism, has a s t a b l e temperature, and is l e s s subject to contanination than surface water resources. But the very high deman-d f o r municipal water frequently precludes the exclusive use of groundwater f o r municipal water supply because of the limited capacity of groundwater resources. Bacteriological non-defec tiveness i s an indispensable requirement. Physical and chemical indicators tend to demonstrate possible pollution i n the water resource o r during water purification and transport. The term raw water refers to water from the surface or under,eround resource, whose q u a l i t y only depends on natural factors and possible anthropogenetic pollution. Water treatment or water purification is a combination of technological processes aimed a t changing the quality of raw water to the required level (Fig. 2.9). The quality of treated water depends on the quality of raw water: not only

on the content of undesirable matter not removed during waOer treatment, but a l s o on the content of desirable matter which was removed during treafment or which does not appear i n the raw water. For example, the lack of minerals in drinking water, c h a r a c t e r i s t i c f o r treated water from surface resources, incidentally causes h e a r t and vessel diseases. The basic requirement for the quality of raw wter intended f o r municipal water supply is its non-defectiveness frcm the toxicological point of view and the s a f e running of technological processes during its purification. The values f o r the maximuin permissible concentration of harmful matter a r e gradually being defined with mre precision. Particularly important is the quant i t y of harmful bacteria and of organic ratter, whose concentration increases the probability of noxious e f f e c t s . The harmfulness of t h i s matter a l s o depends on its combination. Unpleasant flavours and odours which a r e d i f f i c u l t to remove a r e another important factor. Water treatment decreases the content of undesirable components to below the

level of maximum permissible concentrations and increases the s u i t a b i l i t y of the water f o r transport i n the pipeline network. A l l pathogenetic organisms, in particular the large group of Salmonella-Shigella bacteria and viruses, have to be removed by disinfection. Viruses a r e often r e s i s t a n t to current disinfection methods , including :

128

WATER

PRETREATMEN MICROF ILT RAT 10N

PRETREATMEN SEDIMENTATI0 N INFILTRATION, SLOW F ILT RAT I0N

OXIDATION

0 XI D AT ION

C 0AGULATION, SOFTENING

F ILTR AT I0N

'4

A DSORPTON

INFILTRATION, SLOW F ILT R A T 10N

SEDIMENTATION

DES INFECTION

TREATED WATER

Fig. 2.9. Basic ccmbinations of methods of water treatment for municipal water supply. (a)

physical ( l i g h t u l t r a v i o l e t rays, radioactivity

ultrasound, e l e c t r i c i t y ) (b) mechanical ( f i l t r a t i o n

clarification

-

r-radiation, heat,

sedimentation, u l trarnicrof i l t r a -

tion, reverse osmosis, capable of removing 95-99% of bacteria) (c) chanical (chlorination, i . e . addiqg of i t s compounds, other halogens, oxygen e tc. ) (d) oligodynamic (katadynisation and other disinfection methods using various heavy metals: s i l v e r , copper and t h e i r s a l t s ) . An excess of disinfection matter, e.g. chlorine, forms a protection against

pollution during transport i n the pipeline network. Its extinction a t the end of the network m y indicate relevant pollution, which may be of pathogenetic ori-

gin. But chlorination m y a l s o produce adverse effects: trichlorine methane derivatives , produced by reacting chlorine on humine acids, currently occurring

in surface waters, cause the dissemination of cancer according to Maugh I1 (1981). Apart from sanitary requirements, the quality of drinking water should cor-

129 respond to the requirements of economical and continuous transport i n the pipeline system, not causing corrosion or clogging. The optimum water quality for this purpose depends especially on the degree of over-saturation and undersaturation with calcium carbonate CaC03. This s t a t e can be characterised by langelier's index, i . e . by the difference between the actual pH factor of water and balanced pHs, when the protecting a l k a l i n i t y corresponds to tke concentration of carbon dioxide C02

Is

=

PH - PHs

(2.54)

TABLE 2.17

Material

Concrete

0

Saturation index

Asbestocement

Steel & cast iron

0

0

Glass & plastics 0

Oversa tura tion with calcium carbonate

-

as CaC03

- as

Ca

5-10 mg, 1-l

5-10 mg. 1-l 0.05-0.1 mol.1-I

5 rng.1-1

Aggressive C02 Calcium Ca Total a l k a l i n i t y Factor pH Sulpha tes SO:-

-

5 mg.1-1

5 mg.1-1 16 mg.1-I

-

0.8 mm01.1-~ 637

0.8 mnol.1-I 0.8 m1.l-l

-

6.0

250 mg.1-I

250 mg.1-l

15 mg. 1-l

15 mg. 1-l

Suspended matter COD (by pemnganate)

5-10 mg. 1-l 0.05-0.1 -1.1-I

1000 mg. 1-1 75 m g . P

-

15 mg.1-l

~ _ _ _ _ ~ _ _ _ _

~

Degree of aggressivity

5-10 mg. 1-1

Rate of uniform corrosion e m per year (water temperature below 25OC)

1. mild aggressivity 11. medium aggressivity 111. high aggressivity

50

50

-

150

150

Indicators for safeguarding the s t a b i l i t y of water quality during i t s transport and limiting the corrosion r a t e i n pipeline systems. Degree of agqressivity for determining the efficiency of the water treatment process to l i m i t the corrosion rate. The protection of metallic pipelines has to be achieved by a certain degree of oversaturation with calcium, forming a thin internal protective. This can be achieved under conditions of a high content of the t o t a l canponents of carbonic acid

According to S t m (1962), in the case of a low content of these components, a granular porous matter appears instead of a compact f i l m . The

130 aggressivity of water depends on the character of the material i t contains, and has t o be evaluated on the basis of the limiting values of the pH factor, sulphates SO-: and chlorides C1-. Pipes mde of p l a s t i c materials and glass are

chemically f a r more r e s i s t a n t (Tab. 2.17). For the most part domestic water requirements have to be covered by warm water supply. The mass supply of wann water is often accomplished by a s p e c k 1 pipeline network. The quality requirments for mass supply of warm water is a complex subject. Such water should correspond to drinking water standard and must The temperanot cause excessive corrosion o r clogging of the supply network. ture of warm domestic water should be about 6OoC, because higher temperatures increase the corrosion r a t e . Chemical indicators for warm water quality a r e , therefore, more complicated means of achieving the desired balance for limiting corrosion and clogging (Tab. 2.18). These c r i t e r i a a l s o include the content of magnesium Mg before warming and the mintenance of the diphosphorus oxide P205 concentration above 2 mg. 1-l to 3 mg. I-'.

TABLE 2.18

<

60" C

CaC03 + M&03

Factor pH

<

2'5'

8.6

2

-

Content of chlorides i n dependence on CaCO3+M&O

< 4,18 mnol.l-' > 4,15 ml.l-'

+ MgC03

&C03

> >

Total a l k a l i n i t y

Temperature Dissolved solids

1.5 mnol.l-' 1.5 m n 0 1 . 1 - ~

-5

mg.1-l

3

_c

75 mg.l-1 1% mg.l-1

Content of magnesium Mg2' i n dependence on pH and t o t a l a l k a l i n i t y pH

<8,6 t o t a l a l k a l i n i t y 1.5-4 mnol.l-'

4-8 ml .1-1

>8.8

< 42 mg.1-I

Content of f r e e c02 i n dependence on Ca2+, and t o t a l a l k a l i n i t y 0g(Ca2+-a)g0.5 d ( a -Ca2+)=0.5 < 0.5<(a

mg. 1-1 $1 i5

I16

-

- Ca2+)=(1 0.5((Ca2+-a)i1.5

1.5-3.6 -l.l-' 3.6-7.2 mnol.l-'

> 7.2

+)

-1.1-I

--+

mg. 1-l 11.8 s7 i18

Basic c r i t e r i a f o r the quality of warm water supplied by a special pipeline network for ma$s supply: +) before warming, a - a l k a l i n i t y .

2.4.2

Water Requirements for Other Dcmestic Uses

Water requirements for other domestic uses depend on the local conditions, especially on the

131 life-style standard of equipment r a t i o of income and water r a t e s number and age of household members. I n developed countries, the standard of equipment has the greatest influence (Tab. 2.19). TABLE 2.19

Household equipment

ass delivery of warm water, central heating, bathroom Warm water heated locally ba t h r o m Cold running water , shower Outdoor wells, s t r e e t faucets (without running water o r flush t o i l e t s )

Average daily water requirements (1 per capita and day) block of f l a t s family houses

280

170

230

140

150 40

90 25

Average urban and r u r a l water requirements per capita and day and t h e i r relation to the standard of household equipment. Water withdrawals f o r domestic water supply generally exceed the relevant water requirements and a l s o depend on the technical equipment and s t a t e of the supply network, a s well a s on i t s operation and mintenance. Water rates have a regulating e f f e c t , depending on the r a t i o of the family o r individual income and i t s value, but only i f payments a r e derived from current metering. I t is useful to apply water pricing a s a regulating factor of water withdrawals, when the t o t a l water demnd reaches the capacity of the constructed supply systems, o r when the water balance of the relevant area tends t o be passive. Under such circunstances, lower water withdrawals decrease operating costs and delay the extension of the old supply system o r the construction of a new one. Domestic water requirements a l s o depend on the structure of the family, on the age, sex and a c t i v i t i e s of the family members. Nevertheless, the prevailing factor i s the standard of equipment. The crucial moment of a rapid increase i n water requirements is reached when water use i s not r e s t r i c t e d by a v a i l a b i l i t y , a law standard of equipment or high r a t e s influencing l i v i n g standards. The a v a i l a b i l i t y of f r e e time may appear as the next crucial factor f o r a further rapid increase i n water requirements. According to Holman (1961), the structure of t i m e u t i l i z a t i o n i n developed countries during the period 19502000 w i l l not change considerably (except annual leave, which may r e s t r i c t requirements i n the critical s m r period). For t h i s reason, future water d e m d

132 w i l l n o t d i f f e r from p r es en t requirements, which correspond to high l i v i n g standards . Domestic water requirements ( i n cl u d i n g drinking water demand, forming 2-2.5% of i t s value only) have t o be derived from the standard of equipment, occupat i o n and general c u s t o m , sex and age and simply defined as a func tion f o r the individua 1

RI=f ( s

9

0

,E

(1 per c a p i t a )

)

(2.55)

and f o r the household (family) members. Defining t h e averaee p er c a p i t a and day water requirements Rd a s the optimum value which corresponds t o t h e customary s t y l e of l i f e , n o t including excess wastaee, previous equations can be s i mp l ifie d by using c o e f f i c i e n t s a s follows: for the i n d i v i d u al f o r the household

ka, k i kX

m

Rl =

Rd . ka . kx ( 1 pe r c a p i t a )

R f = m.Rd

. ka . k,

( 1 per household)

-

c o e f f i c i e n t of a c t i v i t y ( p r o f es sion and f r e e time)

-

c o e f f i c i e n t of unavoidable wastage

-

n m ber of household ( f ami l y ) members.

The t o t a l domestic water demand is expressed by the sum

k

- c o e f f i c i e n t of l o s s es i n t h e supply system

( < 1.15)

k . . . . . N - category of t h e dwelling standard including subcategories of a c t i v i ties mak

-

number of i n h ab i t an t s i n r e l e v a n t subcategories

Rd

-

o p t h u m water demand which corresponds t o the s t y l e of l i f e (household equipment and a c t i v i t i e s ) .

l h e n a n a l ys i n g t h e n e c e s s i t y and economy of domestic water supply f o r d i f f e r e n t purposes of u t i l i z a t i o n i t is p o s s i b l e tc d i s t i n + s h four c a t e g o r i e s of

water q u a l i t y : A1

-

%-

p h y si o l o g i cal l y b e n e f i c i a l water ag re e a ble i n smell and taste (can be s u p p l i e d by a s p e c i a l network o r b o t t l e d ) p h y s i o l o g i cal l y b e n e f i c i a l water ( i f not a v a i l a b l e , can be replaced by category B ) d r i n k i n g water, as d ef i n ed , i.e. s a n i t a r i l y non-defective water, which cannot cause h e a l t h t r o u b l es or d i s e a s e s , even a f t e r l o n g t e r m u t i l i z a t i o n .

B

-

C

- sanitarily

nm-defective water. The use of water of lower q u a l i t y f o r f l u s h i n g , water and o t h e r purposes r e quire s strict te c hnic a l and hygienic measures t o exclude any co n t act with the human organism.

133

1

I

P HY S l C A L CARE

I

I

CLEANING, WASHING

ORIGINALLY 2001 / c a p i t a / d a y

Fig. 2.10. Water-saving technologies f o r households. Schematic r e p r e s e n t a t i o n of p o s s i b i l i t i e s of waste water s e g r e g a t i o n i n household and'subsequent f e a s i b i l i t y of domestic water re-use. T r a d i t i o n a l system i n black and d o t t e d , d a t a in brackets

.

The b a s i c precondition f o r a high standard of l i f e can be ensured by supplyi n g 250 1 p e r c a p i t a and day (Tab. 2 . 2 0 ) , i f used i n a proper way. Supplying higher q u a n t i t i e s only forms favourable conditions f o r water wastage. The same standard can be achieved by applying unconventional water-saving techniques t o lower water withdrawals and/or by r e c y c l i n g segregated waste waters: Waste water from personal washing, b a t h i n g and laundry can be used without any treafment f o r t o i l e t r i n s i n g , garden watering and outdoor washing (Fig. 2.10). P o l l u t i o n by d e t e r g e n t s may r e s t r i c t t h e use of such water f o r i r r i g a t i o n . This can be precluded by usiqg s u i t a b l e d e t e r g e n t s , namely by using d e t e r g e n t s which have f e r t i l i z i n g e f f e c t s and do n o t forni carcinogen remnants. Waste water re-use

i n households may decrease t h e p e r c a p i t a water requirements of the

h i g h e s t s t a n d a r d o f l i f e t o some 130 1 p e r day, thus enabling t h e growing water demands f o r i r r i g a t i o n and street washing t o be covered, i n many cases without an extension of the e x i s t i n g water supply network.

134 TABLE 2.20

Component

Water requirements Per capita and day (1) (%I

Drinking A1 Meal preparation

15 20

Cleaning

10 50

20

10

4

30

Household t o t a l Public u t i l i t i e s & heating

Toilet rinsing

60

C

Garden watering

Per. Harmless Health Agreecapita bene- a b l e t o and day f i c i a l drink (1) (%)

5

+

2

A-C

-

+

+

+ W W

42

+ +

60

24

-

12

30

12

200

80

200

80

+

+

+

50

20

50

20

+

+

+

105

~

Unavoidable losses

+ +

+ 2

Laundry (washing)

B

Water q u a l i t y

2

3

6 24 8 4

Dishwashing Physical c a r e

Total

Urban water requirements t o t a l

-

w w

-

-

~

250 1 per c a p i t a and day

I d e a l s t r u c t u r e of per c a p i t a and day urban water usage r e s p e c t i n g modern s t y l e of l i f e , b u t not including unnecessary wastage which does n o t improve the living standard. Corresponds t o water requirements of garden cities i n a h m i d c l i mate. Symbols: + y e s , - not necessary, W warm water 2.4.3

Urban Public Water Requirements

Urban public uses of water include (a)

p u b l i c and technical u t i l i t i e s

(b)

h e a t i n g and b o i l i n g (steam, heated and warm water networks)

-

see para-

graph 2.4.2, Tab. 2.18. ( c ) f i r e extinguishing (d) water and waste water treatment, cleaning of water supply and sewer system. Public and technical u t i l i t i e s embrace a l l services including c u l t u r a l , schools, h o s p i t a l s and o t h e r s a n i t a r y s e r v i c e s and a d m i n i s t r a t i o n , b u t n o t ind u s t r i a l and a g r i c u l t u r a l production. Water use f o r t h i s purpose a l s o includes

135 street washing and watering of gardens and parks , playgrounds an6 graveyards, and cleaning of transport vehicles (Tab. 2 . 2 1 ) . TABLE 2.21

\(later requirements

Per employee daily

Tdater requirements

60

Theatres , cinem s

Bar

300

Restaurant , canteen Snack bar, canteen

450 400 300

Nurseries, creches Kindergar ten Schools

Shops, s t o r e s

CaG, wine c e l l a r Services not using water for processicg D i r t y and dusty workshops Hairdressers Photographic laboratories

80

Per visit o r daily 5

120 60

25

40

h i v e r s it i e s Youth clubs

25 60

m n a s ium

180 200 800

Sauna

250

3

Match auditorium Travellers by r a i l o r bus

3

Sales rooms

60

Butchers ' shops

80

Per one

100

washing

Chemists Sanitary services Railway stations Off ices

80 6o

Car washing

500

6o

Lorry, bus washing

900

per bed daily Hotels de lux secocd class Guest houses hostels Hospidls

Comnica tions 1) Public spaces 1)

700

Tennis baske t b a l l

250

Social care homes

500

IJrban public water requirements:

1000 3000

per s q . m . daily

1200 500 2 00

Convalescent homes

-

Playgrounds

3-5 3 - 5 1 - 2 10 m3. haper season

Parks

2)

1200

Gardens Grakyards

2)

3000

2)

200

1) 240 days a year,

2 ) i n humid c l i m t e .

The quantity of water used f o r heating i s relatively small and relatively unimportant f o r water balance computations. The quantity of water used for water

treatment and cleaning the water supply and sewer system can be derived as a percentage of the t o t a l amount supplied. When using water f o r f i r e extinguishing,

136 temporary troubles or breakdowns i n the public water supply may be permitted. Ida t e r requirements f o r public uses therefore depend. (1) on the area of the c m u n i t y (washing and watering of c m u n i c a t i o n l i n e s and other public areas) (2.57)

Ak Rak

-

area washed and watered

(m2)

s p e c i f i c water demand per square u n i t

(1 .m-')

(2) on the number of inhabitants (per capita and day water demands i n public utilities)

n

-

number of inhabitants

Rbk - average per capita and day uses i n relevant

public u t i l i t i e s

(m3 per capita and day)

( 3 ) on the number of public, c u l t u r a l and o t h e r s o c i a l u t i l i t i e s (on the number of outdoor v i s i t o r s , requirements n o t included i n the number of inhabi-

tants

-

h o t e l s , h o s t e l s , selected schools, s a n i t a r y , s p o r t , c u l t u r a l and trans-

port u t i l i t i e s e t c . )

m

-

number of v i s i t o r s i n relevant u t i l i t i e s

Rck - per capita and day uses of v i s i t o r s i n relevant public u t i l i t i e s .

The per capita and day requirements of the inhabitants and v i s i t o r s can be es timated a s the f i c t i t i o u s uses of relevant personnel. The q u a l i t y of water f o r public u t i l i t i e s t h e o r e t i c a l l y corresponds t o the mentioned four categories f o r domestic water uses. The quantity requirements depend on the climate, on the s i z e of the relevant l o c a l i t i e s and on the standard of the relevant public u t i l i t i e s . Their t o t a l reaches some 10%of the domes t i c water demand f o r unimportant townships, 30% f o r big municipalities and sane 50% f o r large c i t i e s and spas. Water f o r f i r e extinguishing has t o be withdrawn from the water supply network, from s p e c i a l reservoirs and/or d i r e c t l y from a water resource. The q u a l i t y requirements f o r such water should safeguard the uninterrupted operation of the extinguishing equipment eani tary postulates

.

- i.e.

preclude clogging

-

and a l s o secure the basic

137 TABLE 2.22

F i r e Specific load water requirements (kg)

Period between the alarm and extingu ish ing

bin>

(1.s-l)

5

0.128

3

50 100 120 180

0.170 0.220 0.240

10 20 30 40

0.300

Distance of the fire brigade

Surface affected by f i r e Minimum Collec- Industry tive with ccmdwell- bus t i b l e ing products

(km) 0.5 3-6 10-13 18-22 28

(m2)

16 28 45 62 79

44

95

72

112

148 224

152 192

337

300

Parameters f o r determining f i r e water requirements: s p e c i f i c water requirements f o r d i f f e r e n t f i r e load and surface assumed to be affected by f i r e a t the beginning of f i r e extinguishing. A minimum w l m e of a t l e a s t 75 'm or a maximum d a i l y withdrawal of 3 hours Should be reserved f o r f i r e extinguishing purposes i n the reservoirs of the relevant supply network. The capacity of the water resources and intake m u s t allow a supplementation of t h i s volume f o r 12 hours i n i n d u s t r i a l e s t a t e s , f o r

24 hours i n big towns and f o r 36 hours i n small townships. The t h e o r e t i c a l requirements f o r f i r e extinguishing correspond to the s i z e of the area attacked by f i r e a t the beginning of extinguishing. The s p e c i f i c 2 water requirements, corresponding t o 1 m of the area attacked, depends on the s t r u c t u r e and material, expressed a s f i r e load. This load has t o be determined by converting the amount of combustible matter present i n the volume of wood of the same heating value. I t i s n e i t h e r advantageous f o r economical to safeguard water f o r extinguishing s i n g l e family houses, simple and small buildings, o r

small l o c a l i t i e s with water requirements which do not exceed 5 1.s-'. Water requirements f o r f i r e extinguishing a r e determined by the following formula Re =

6 . Ae .

Rse

Re - water requirements f o r f i r e extinguishing

A,

- area

attacked a t the beginning of t h e f i r e ex t i n w i s h i n g

(1.s-l)

(2.60)

(1.s-I) (m2>

6 - c o e f f i c i e n t which expresses cperational d i f f i c u l t i e s during f i r e extinguishing (1 t o 1.3, max. 1.5, depending on v e n t i l a t i o n , evacuation of persons, types of combustible matters e t c . ) R

~ s~p e -c i f i c requirements of water f o r f i r e ex tinghishing

(I.s-'.m-*)

138 The s i z e of the area attacked depends i n part on the type of building and then on the time i t takes the f i r e to f l a r e up and the time i t takes the firebrigade to a r r i v e , i . e . on the distance of its headquarters (Tab. 2.22) and on the method of the f i r e alarm signal. For storage tanks, s i l o s and reservoirs the theoretical value of t h i s area is a t maximum 150%of the area which can be attacked by f i r e . The water pressure i n hydrants should be a t l e a s t 0.2 MPa. The water requirements for water treatment cover (a)

f i l t e r washing sludge discharge of defecators and s e t t l i n g basins.

(b) The water requirements for f i l t e r washing a r e expressed by the formula Rw =

f K

.t .v

. x . 100

(% of treated water) (2.61)

. (1-e-It)

f

-

I

- washing

t

- time

x

-

content of suspended matter i n raw water

(mg.1-I)

k

-

sludge capacity of the f i l t e r

(m .m )

V

- volume of the f i l t e r

f i l t e r surface intensity

of washing

3

-3

(m3

Leaving aside the quantity of suspended matter i n the f i l t e r , t h i s equation can be simplified to

a =230.3

. log v t V . t

v

-

t

- duration of the f i l t r a t i o n cycle

filtration rate

(% of treated water) (%)

(hrs )

The water requirements for the cleaning of defecators o r s e t t l i n g basins without pumping a r e R

u

=

XI. c

100

(% of treated water) (2.62)

x'

-

concentration of suspended matter which enters the space f o r thickening

(g.1-l)

c

-

concentration of suspended matter i n the thickened sludge

(g.1-I)

Pumping changes the previous formula t o

Ru =

R.t . Qt

-

100 (% of treated water) (2.63)

139 Q, - output of the sludge pmp

(m3. s-')

T

-

duration of sludge pumping

(sec)

t

-

period of sludge pumping

(set)

Qt

-

treated water quantity

3 -1 (m . s )

2.4.4

Management of Water Delivery and Disposal

The flow chart f o r an assessment of water requirements, a s well a s t h e i r projection f o r the evaluation of a l t e r n a t i v e scenarios and f o r the operational management of water withdrawals i n the mass supply network, a l s o embraces ind u s t r i a l and a g r i c u l t u r a l water supply including i n f r a s t r u c t u r e (Fig. 2.11). The value of the optimum water demnd f o r population, enabling the development of a high standard of l i v i n g , was derived i n the previous paragraph fixed a t 200 1 per capita and day f o r domestic purposes and 50 1 per capita and day for urban public uses (without recycling). These figures include a reasonable percentage of water wastage and a r e t o be regarded a s planning and operational l i m i t s which mst n o t t o be exceeded. They a l s o contain a reasonable reserve f o r an increase i n present water demands through - the extended use of washing-machines, - more Lrequent bathing, showering and general physical care, -

-

the extended use of d i s h washers, the extended practice of garden i r r i g a t i o n and out-door washing (Tab. 2.20).

These figures do not include water requirements f o r home swimming-pools o r a i r coolers. Using the flow c h a r t f o r the management of withdrawals (Fig. 2.11), these have t o be reduced hierarchically depending on the socio-economic losses which occur a s a consequence of the reduced water d e l i v e r i e s . The course of water withdrawals which f u l f i l l municipal and r u r a l water demands is non-uniforni. Tnis course depends on the cycle of economic and s o c i a l a c t i v i t i e s , i n p a r t i c u l a r on

-

the organisation of production, services and other s o c i a l a c t i v i t i e s ,

-

the l i v i n g standard, custcms and c u l t u r a l standards which serve to form the

relevant l i f e - s t y l e . I n the course of the y e a r , minimum municipal water requirements occur during holidays - w i t h the exception of holiday r e s o r t s . I n Central European conditions, a noticeable minimum can be observed a t the end of July and beginning of August and there i s a l s o a periodic depression durinn February. Maximum water requirements, which d i f f e r less from the average values than the minimum values, occur very often during October o r November and sometimes a l s o before C h r i s m s . The weekly minimum occurs on Saturdays and Sundays. The course of water deliveries depends on economic a c t i v i t i e s on weekdays, and on the l i f e - s t y l e during holidays. The d a i l y minima

occur a t night, and the m x i m

i n the evening, w i t h a

140 POPULATION number number of households) s t a n d e r d of equipment S t r u c t u r e : agesex, profession, free time, habits 'ER CAPITO ;ONSUMPTION

PUBLIC AREAS size population number number of visitors

INDUSTRY AG RIC U LT U RE tons of production hectors i r r i g a t e d

PER CAPITO CONSUMPTION

SUPPLIED FROM MUNlC IPAL SUPPLY SYSTEM

ALANCE POSlTlV

Fig. 2.11. Block diagram f o r determination of municipal water requirements and management of water delivery during periods of a passive balance of water reSources and needs. less considerable mxirn7m values i n the morning and a t noon (Fig. 2 . 1 2 ) . The mximurn and minimum values of water withdrawals from the municipal water supply network can be derived from the average values by using coefficients a s follows : Maximum and minimum t o t a l d a i l y average water requirements :

141

Rm

= Rd

. ‘d

(mJ per hour)

fld - average d e i l y requirements (total of the

(2.64)

(n3 p e r hour)

domestic and public uses) cd - coefficient of the daily non-uniformity ( = 0.9 for minimum, 1.05 - 1 . 5 f o r maximum, lower values correspond to b i g c i t i e s , higher to srilall conmunit i e s 1 ?iaximum and minimum water requirements per hour Rh = Rrn

.

(m3 per hour)

‘h

Rh

- maximum d a i l y

ch

-

average demand

(2.65)

(m3 per hour)

c o e f f i c i e n t of the per h o w non-unifonnity (% = 0.15 - 0 . 6 f o r per hour minima, 1 . 5 - 2 . 9 f o r per hour maxim, likewise depending on the s i z e of the settlement).

i

1 hrs

Fig. 2.12. Graphic representation of diurnal fluctuation of water deliveries i n a municipal supply network and c o e f f i c i e n t s of per hour fluctuation: 1 - town with 50,000 inhabitants, 2 - d i s t r i c t of workers, 3 d i s t r i c t of clerks and salesmen, 4 - average d i s t r i c t .

-

Water losses which occur during mass water supply f o r the population a r e caused by (a) wastage - i . e . i n the unused release of water from the network, (b) technical shortcomings and defects of the p r i v a t e indoor i n s t a l l a t i o n s ,

142 ( c ) the operation, technical shortccmings and d e f e c t s i n the public network i n c l water r e s e r v o i r s .

.

These l o s s e s can be c l a s s i f i e d a s (a)

t e c h n i c a l l y removable,

(b)

inevitable losses.

The percentage of water wastage depends not only on t h e s u i t a b i l i t y of the r e l e v a n t technical equipnent, b u t a l s o on the economic tools and the degree of o f f i c i a l and personal r e s p o n s i b i l i t y and d i s c i p l i n e . Technical shortcomings and d e f e c t s depend e s p e c i a l l y on the technical state of the water supply network, which i n i t s e l f depends on the q u a l i t y of the m a t e r i a l , f i t t i n g s and o t h e r equipment, on the state and u t i l i z a t i o n of measuring equipment a s w e l l a s on the q u a l i t y of t h e workmanship, m i n t e n a n c e , method and d u r a t i o n of the operation,

i . e . t h e ape of the system. The average water l o s s e s of the p i p e l i n e network should n o t exceed lo%, and a t the end of the s e r v i c e l i f e of t h e system n o t nore than 15%of water w i t h drawa Is . From the economic p o i n t of view water losses have two basic a s p e c t s : ( a ) the genera1 economy of water resources u t i l i z a t i o n , which can be analyzed on the b a s i s o f water balances, (b) the cost-effectiveness of the operation of t h e water supply network depending on the water p r i c i n g and water metering system.

These two aspects d i f f e r i n d e t a i l and o f t e n generally, a s w e l l : A s u b s t a n t i a l p a r t of t h e withdrawn water is n o t used b e n e f i c i a l l y , although paid f o r , and does n o t , t h e r e f o r e , c o n t r i b u t e t o the s o l u t i o n of r e l e v a n t water balance problems. On the o t h e r hand, withdrawn water, although n o t paid f o r , nay be b e n e f i c i a l l y used. The loss from the cost-effectiveness p o i n t of d e w is formed by the d i f f e r e n c e between the q u a n t i t y supplied and the volume paid f o r . Water used f o r f i r e extinguishing, street watering and emergency water supply i n

cisterns i s o f t e n not s u b j e c t t o invoicing, y e t cannot be considered a s a loss from the balance p o i n t of view. Mass water supply i s metered ( a ) d i r e c t l y - by means of measuring instruments, mainly gauges and water meters , (b) i n d i r e c t l y - on the basis of the energy consumption for its supply, o r pump output . The course o f water d e l i v e r y and water losses cannot be followed up i n the necessary d e t a i l , because water supply networks a r e n o t equipped with a s u f f i c i e n t number of measuring devices. The manner of invoicing and water p r i c i n g , o f t e n lump s m which bear no r e l a t i o n t o the water q u a n t i t y r e a l l y delivered, is n o t s u f f i c i e n t l y bound t o the desired r e a l economy t o supply water f o r benef i c i a l uses only. The goal of the assessment of lump suns and o t h e r charges is

143 to cover the operation and maintenance c o s t s including p r o f i t , i f required. Incoherent metering, accompanied by imperfect measuring equipment and the ins u f f i c i e n t q u a n t i t y and wrong l o c a t i o n of t h i s equipment, serves to c r e a t e f i c t i t i o u s l o s s e s . Under such circumstances, water p r i c i n g does n o t form a n e f f e c t i v e tool f o r economising on water u t i l i z a t i o n . Measures f o r l i m i t i n g r e a l l o s s e s i n water tanks, p i p e l i n e s and indoor i n s t a l l a t i o n s include ( a ) a well-equipped,

prompt maintenance and breakdown s e r v i c e f o r the im-

d i a t e r e p a i r of apparent and discovered t r o u b l e s , (b) the execution of r e p a i r s , reconstruction and modernization of the network i n h a m n y w i t h the technological development and with its technical state, e s p e c i a l l y with i t s corrosion, clogging and ageing, ( c ) the l i m i t i n g of overflow by an e f f e c t i v e s i g n a l l i n g and blocking system, (d) the systematic measuring of a l l important withdrawals and the s y s t e m -

t i c checking of lump sums and excessive withdrawals, ( e ) the u t i l i z a t i o n o f water meters i n a q u a n t i t y which corresponds t o the delivered water q u a n t i t y , ( f ) the adherence t o the recommended terms f o r the c a l l i b r a t i o n of water

meters and p e r i o d i c maintenance, ( g ) the systematic checking of water losses i n the supply system, (h)

t h e equipping of the network with r e a l l y w a t e r t i g h t yalves and closures,

( i ) the introduction of a n e f f e c t i v e system f o r checking t h e i r locking mechanism. The measures f o r l i m i t i n g water wastage a r e simple, b u t e f f e c t i v e . They include : ( a ) systematic water metering and the l i m i t i n g of anonymous non-metered withdrawals by the i n s t a l l a t i o n of water meters n o t only f o r the main u s e r s , b u t a l s o f o r housing u n i t s , ( b ) an e f f e c t i v e water p r i c i n g system, introducing water p r i c e s which increase with over-excessive water d e l i v e r i e s ,

( c ) the u t i l i z a t i o n of water meters i n a q u a n t i t y which corresponds t o the delivered water q u a n t i t y , the automatic c o n t r o l l i n g of non-metered escapes of water, ( e ) the instalment of a u t w t i c s t o p and discharge valves, locking gear, s e l f - a c t i v a t e d timing devices e t c . , (d)

( f ) the s y s t e m t i c checking of water l o s s e s i n and a u t m t i c checking of escapes from the supply system, (g) the a p p l i c a t i o n of devices f o r waste water segregation and accumulation, and secondary using of water p o l l u t e d by washing and showeriqq f o r t o i l e t f l u s h i n g , outdoor washing and garden watering. Domestic sewage i s to be accumulated and/or t r e a t e d i n o r d e r t o avoid the

144

contamination of surface and groundwater resources. I t m y be, under appropriate environmental conditions and depending on the required degree of control (Fig. 2 . 1 3 ) , discharged i n t o a body of water i f a s u f f i c i e n t discharge with adequate dissolved oxygen i s a v a i l a b l e , so t h a t the s e l f - p u r i f i c a t i o n processes would not cause any nuisance. The a p p r o p r i a t e method of domestic waste water disposal depends, t h e r e f o r e , on e f f l u e n t q u a n t i t y and q u a l i t y a s w e l l a s on l o c a l environmental c o n s t r a i n t s .

38 Fig. 2.13. Basic sys terns of domes t i c waste water d i s p o s a l , r e s u l t i n g i n a rnoder a t e l o c a l (scheme l ) , moderate serni-centralized (schane 2 ) , and s t r i c t p o l l u t i o n c o n t r o l (scheme 3 ): KL - k i t c h e n , s c u l l e r y , laundry, R -bathroom, showers, washsedimentation b a s i n s , WC - t o i l e t , ST - s e p t i c tank, SC - sludge container, S tank, CH- chemical treatment, I N - i n f i l t r a t i o n , AE - a e r a t i o n , b i o l o g i c a l f i l ter e t c . , AP - a e r o b i c pond, WTP - waste water treatment p l a n t .

-

2.5

INDLTSTKIAL WATER SUPPLY AND RE-TEE SYSTEMS

I n d u s t r i a l supply is enabled by i n d u s t r i a l water supply and disposal systems ,

i . e . sets of s t r u c t u r e s , technoloqical equipment such a s measuring and c o n t r o l l i n g devices with a s s o c i a t e d feedbacks which secure the withdrawal and treatment of water, i t s d i s t r i b u t i o n and c i r c u l a t i o n , a s w e l l as waste water treatment and

145 recycling, sludge disposal and the harmless discharge of polluted water i n t o appropriate r e c i p i e n t s . Process water i n industry includes a l l water needed f o r ( a ) processing, i . e . water e n t e r i n g the product and serving functional p u r poses, (b) (c)

mining and hydraulic t r a n s p o r t , cooling and a i r conditioning,

(d)

b o i l i n g and h e a t i n g , ( e ) general use (cleaning, showering, drinking and o t h e r personal uses i n industry). Process water does n o t include water used f o r water power generation. The use of water i n industry is heterogeneous, and the r e l e v a n t supply and disposal systems a r e complicated; these include (a) (b)

open c i r c u i t operations - i n one process successive re-use operations

-

of used water i n o t h e r processes of the same i n d u s t r i a l p l a n t , of waste water i n o t h e r p l a n t s o r i n a g r i c u l t u r e , of municipal waste water i n i n d u s t r y , ( c ) r e c y c l i n g operations p a r t i a l c i r c u l a t i o n ( e . g . of cooling water) closed c i r c u i t operation, i . e . c i r c u l a t i o n and recycling of a l l waste waters (Fig. 2.14). I n the open c i r c u i t system the water withdrawal is discharged i n t o r e c i p i e n t water resources a f t e r use i n one process. The value of the water withdrawal W corresponds t o the water requirement R , i . e . t o the sum of the water e n t e r i n g the product o r s e r v i n g o t h e r functional purposes, r e t u r n flow and the water losses R = W = C 1 +

en k=l

k

+

(1.s-l)

(2.66)

( 1.s-l)

(2.67)

[dater consumption i n the open c i r c u i t system is

F

-

r e t u r n flow ( e f f l u e n t )

- w a t e r consumption f o r functional purposes i n c l . water e n t e r i n g the product 1 A1 t o A k - water l o s s e s i n t h e supply, d i s t r i b u t i o n and d i s p o s a l system C

- water

, A ~

requirements f o r waterlwaste water treatment

The successive re-use of waste waters is characterized by t h e supply of water i n q u a l i t i e s which d i f f e r from the q u a l i t y requirements of t h e r e l e v a n t produc-

146

C.

n

d.

n

Fig. 2.14. I n d u s t r i a l water supply, d i s t r i b u t i o n and waste water disposal systems: ( a ) open c i r c u i t system, (b) successive re-use system, ( c ) p a r t i a l recycling system, (d) closed c i r c u i t system. WfP - water treabnent plant, Wwrp waste treatment plant. tion process. 'fie basic problem of the d i r e c t re-use of water is: (a) securing the quantity of water f o r successive technological processes taking i n t o account the time schedule and hierarchy of water requirements, (b) safeguarding the quality of the water f o r the following process, which depends on the q u a l i t y of the preceeding one, and t h e i r schedule on the basis of the decreasing water q u a l i t y , i n order t o economize on the water treatment e.g. by segregation of waste waters, re-use of important substances of waste waters etc. During i n d u s t r i a l processes, water i s used - i n contact with the material or product without a thermic impact (category A) o r without a thermic impact (catezory B )

-

i n closed systems without any contact with the raw material o r product (cate-

gory C), (Fig. 2.15, Tab. 2.23). The c r i t e r i a f o r water q u a l i t y which safeguard successful water re-use and re-cycling a r e s m r i z e d by Appleyard and Shzw (1974) a s follows : (a) (b)

low content of suspended matter, low aggressivity,

147 Cotegory

Groups o f

Groups o f

Waste water

o f treated water

water uses

wastes

treatment

MINING AND TRANSPORT

a

i

W

+ D

tzy

GENERAL USE

u

t

I

W

Lz

I-

2

0 0

U O

Lz W

I-

s

h L

0 0, c

0"

~-$IBOILING AND^ STEAM POWER

indirect external water re- use 1

A

II

._

2

I::/

= re-use --- -in_.. agriculture

Fig. 2.15. Schematic r e p r e s e n t a t i o n of heterogeneous water q u a l i t y requirements necessary f o r r e l e v a n t groups of i n d u s t r i a l processes. These processes r e s u l t i n heterogeneous q u a l i t y of waste waters, t h a t a r e t o be t r e a t e d i n one waste water treatment p l a n t and subsequently disposed of o r re-used, both i n industry and a g r i c u l t u r e : r - water r e c y c l i n g , F; - waste waters, C - water consumption, F - e f f l u e n t , W - water withdrawal. (c) (d) (e)

no tendency t o s e p a r a t e s a l t s which a r e d i f f i c u l t t o d i s s o l v e , bacteriologically reliable, no tendency t o c r e a t e b i o l o g i c a l d e p o s i t s , s u i t a b l e pH, s u i t a b l e content of dissolved matter and acceptable odour.

(f) Current water treaiment processes a r e o f t e n inadequate when it comes t o gaining water of such q u a l i t y from waste water. The t r e a t e d waste water contains excessive q u a n t i t i e s of s a l t s , including ions of amnonim and phosphorus, and a l o t of organic matter, dissolved o r suspended, which is b a c t e r i o l o g i c a l l y dangerous and forms foam. I f t h e c u r r e n t simple treatment processes a r e n o t capable of a t t a i n i n g water of s u i t a b l e q u a l i t y , the following physical and chemical processes should be applied:

148

TABLE 2.23 Water i n contact with the product o r with the raw mat e r i a 1 without with heating heating

[dater qua li ty indicator

Tempera ture Suspended matter

-

-

OC

mg . 1

2001)

30-45

\dater without any contact with the product

Temperature of the medium 8OoC 80-4OO0C 4OO0C

25-28

(28-40

<40-45

20-30

10-20

5-10

20

1c-20

1000

Fat and o i l products

-1

mg.1

6.5-9

-

PH

m o l . 1-1

-

-

Carbonate content mnol. 1-l

-

-

Total content

6,6-8,5

6,5-8,5

-

( 7

10

6,5-8,5 (5

Mp + Ca

ME + Ca

1,2-3,5 1,5-2,5+

1,5-3 1-2'

<4

<3,5

1,5-2,5 0,5-2+ (3

Dissolved m t t e r

m01.1-'

Chlorides C l -

mg. 1-1

-

-

(2000 (1300

Sulpha tes SO24

mg.1

-1

-

-

Iron Fe

mg. 1-1

-

-

< 350 <350 < 500 < 600

C3emica1 oxygen demand by p e m n g a n a te by bichrcma te Total biochemical oxygen demand BOD Rioel ements Nitrogen N Phosphorus P

< 20 < 20

< 800 < 150

< 250

< 20

-1 mg .1 -1 mg. 1

-

-

100-150

mg. 1-l

-

-

15-20

10-15

10-15

mg.1-1 mg .l-1

-

-

50-80

50-80

-

lo1)

-

235

-

2 $5

-

Quality indicator f o r c i r c u l a t i o n water (+ supplementary water) according to information from COMECON (1976): 1) f o r f l o t a t i o n (a 1 coagulation with low doses of ingredients irL order t o decrease the cont e n t of the suspended n n t t e r , (b) sorption with a c t i v e charcoal - i n the case of high q u a l i t y requiremen ts , (C) using ion exchanges - especially to eliminate the s a l i n i t y and metallic ions i n exchange f o r sodium, hydrogen and hydroxyl, (e> reverse osmosis

-

f o r an e f f i c i e n t iemoval of orpanic m t t e r and har-

149 t e r i a as well a s of suspended and dissolved anorganic matter, ( f ) e l e c t r o d i a l y s i s - f o r the separation of dissolved m t t e r , i n c l u d i w a c i d s , bases and s a l t s , (g) separation of foam - e s p e c i a l l y f o r the separation of detergents, (h) ozonization - f o r d i s i n f e c t i o n and decrease i n turbidity and content of organic matter, ( i ) using i m b i l i z e d enzymes

-

i n order to remove dissolved organic matter

including phenols and i n order t o decrease the content of pathogenic gems, ( j ) fermentation and s t e r i l i z a t i o n - t o remove s u l p h i t e waste liquors e t c . The basic equations f o r successive water re-use a r e (Fig. 2.14b) (2.68)

(m3 .s -1) Qi

-

C

- t o t a l water consumption

(2.70)

excessive inflow t h a t i s to be diverted without use o r defic.it t h a t is t o be made up from other sources.

Ci - water consumption for functional purposes including water entering the pro-

duct i n the s i n g l e process i. Apart from the mentioned d i r e c t internal successive waste water re-use, ind i r e c t external water re-use a l s o e x i s t s , i . e . repeated use of the same water along a r i v e r by d i f f e r e n t users, formed by the discharge of waste waters i n t o water courses and by its successive withdrawal (Fig. 2.15). The r a t i o of the i n t e r n a l successive water re-use i s as f o l l m s : k (2.71)

R

- the t o t a l water requirements needed f o r relevant technological purposes

(m3 .s -1 , m3)

W

-

(m3.sV1, m3)

the t o t a l water withdrawals

The r a t i o of the external water re-use is expressed by the formula lr

re

=

C W k=l k

Qb

Qb

-

(2.72)

the guaranteed stream f l m used f o r the compilation of water balances

150 The t o t a l r a t i o of water re-use is expressed by t h e i r product

rt

=

re

. ri

=

%

k= Rk

(2.73)

Qb

Generally:

(2.74) Q, Qr

- minimum monthly -

discharge (98% of guarantee)

guaranteed yield of reservoirs

?he expression in brackets equals the t o t a l water consumption, The repeated use of the same water inside a closed c i r c u i t is called water recycling. Water quality requirements c a l l for water to be treated, a t l e a s t by cooling a f t e r each cycle. I n the case of an open system, part of t h e water quantity enters the circulation system and the r e s t is used once only or successively (Fig. 2 . 1 4 ~ ) . Water requirements i n a system with p a r t i a l circulation a r e expressed by the sum

The actual water requirements a r e substantially lower and are covered by the water withdrawal, which replaces the effluent of waste waters and feed water i n order to replace losses and regenerate the water quality of the c i r c u i t

(2.76) The water consumption is (m3 .s -1)

(2.77)

The volume of water i n the circulation system depends on the recycling r a t e and, therefore

Vo Vo

=

Ro

.

tc

(m3

(2.78)

- volume

of water i n the circulation system, whose regular exchange safeguards the regeneration of water quality

tC- recycling r a t e

(s)

In the closed c i r c u i t operation the effluent i s limited to that quantity

151 which enables the regeneration of the water q u a l i t y (Fig. 2.14d)

The water withdrawal W i n such case only covers the water consumption, i.e. the consunptive use incorporated i n a product, by-product and waste material plus water losses

w = c

1

+ f

k=l

a

(m3.s-I>

k

(2.79)

’he intensity with which water is recycled or successively re-used depends on the type and degree of pollution. The closed c i r c u i t operation often requires canplicated and expensive equipment. Water consumption i n industry consists of the consumption required to regenerate the consumption during processing C P ’ the water quality C and losses during treatment, distribution and recycling. q

c = cP + cq

+ k=l

The regeneration of the water treatment, clearing, dustry, water requirements by the supplementary water

k

(m3.sT1)

(2.80)

water q u a l i t y includes water treatment and waste sludge blow-off e t c . During water recycling in ina r e covered by the sum of the recycled water Ro and W abstracted from the resource.

The internal recycling coefficient is the r a t i o r.

1

= --RO

R

-w

W + Ro - 7

The.ratio of the water consmption is expressed by n (2.82)

The r a t i o of the water consumption f o r closed c i r c u i t systems equals almost 1.

A s was mentioned already, water consumption consists of the consmptive use by a product U1, a by-product U2 and by means of wastes U a s well as by return3 able and3non-returnable losses and, therefore Ui + A r + A n i=l (2.83) rc = W

The r a t i o of the water consmption has t o be analyzed separately for the supply, water treatment and recycling system and for water entering the product,

by-product and serving other functional purposes. The relevant values often depend on the season, being. higher i n sumner due t o the higher evaporation r a t e . The water consumption during water supply, recycling and water treatment consists of non-productive losses only. The consmptive use during the technological process of water treatment is a pure loss from the production point of view. These losses can be reduced by technological and operational measures including maintenance, a s well a s by a decrease i n water requirements i n the production processes. The beneficial use of water i n industry can also be expressed by the r a t i o of withdrawal u t i l i z a t i o n

w1

=

-

W - F W

(2.84)

and by the r a t i o of losses

w 2 =

W - F - W - F - R W + R0

(2.85)

Basic indicators of the economy of water use i n industry a r e the water requirements per u n i t of product and the water consumption per u n i t of such a product a s w e l l a s the waste load generated per u n i t of production. Their values depend on each o t h e r , on water recycling and on the technology of prQduction and of water supply. The basic interrelationships can be expressed conceptually i n the form of a j o i n t function:

R'

- water

requirements per u n i t of production

'C - water consmption per u n i t of production

3

(m . t

-1

3 -1

(m . t

)

)

'N

- waste

ri

-

i n t e r n a l recycling c o e f f i c i e n t

A

-

combination of production process and product mix

B

- nature

C

- producFion technology including technology of waste material processing, operating r a t e

load generated per u n i t of production (t.t-')

of raw material used, which a l s o influenced by-product production and waste material processing i n c l . material recovery

D - water q u a l i t y (water q u a l i t y indicators q l , q 2 , . E

-

M1

- water

P$

-

.. .qn)

law and order, administration, the e f f i c i e n c y of t h e i r function r a t e s and cost of water treatment

c o s t of waste water treatment and e f f l u e n t disposal r a t e s .

153 Water consumption, with t h e exception of cooling water, water f o r mining and the use of water i n t h e food i n d u s t r y , does not generally form a s u b s t a n t i a l p a r t of i n d u s t r i a l water demnd. Limiting water requirements serves t o decrease the q u a n t i t y of waste waters and water consumption, but need not n e c e s s a r i l y lead to a decrease i n the waste load generated, whlch depends more on the production technology. The i n t e r r e l a t i o n s h i p between wa tsr requirement and water consumption is complicated, not only i n terms of the q u a n t i t y of waste water, but a l s o of its q u a l i t y , e . g . the environmental need t o d i l u t e waste water. The s e l e c t i o n of a s u i t a b l e technology from the water resources point of view requires an a n a l y s i s of the combinations of water requirements, water consimption and waste loss penerated per u n i t of production. The decision has to be taken on t h e b a s i s of an economic evaluation of the environmental a s p e c t s of relevant production scenarios (Fig. 2.18). Water f o r Processing, Mining and Hydraulic Transport 2.5.1 I n t h e course of mining and hydraulic t r a n s p o r t water comes i n t o d i r e c t cont a c t with the intermediate or f i n a l product without any thermic impact. During processing water comes i n t o c o n t a c t with t h e product o r e n t e r s the product m i n l y a s a c c o l i n g o r heat-carrying m a t e r i a l . The q u a l i t y requirements f o r water which comes i n t o c o n t a c t with o t h e r products without any therinic changes depend s u b s t a n t i a l l y m the nature , q u a n t i t y and maximun s i z e of the s o l i d p a r t i c l e s , which should be s p e c i f i e d f o r t h e relevant use. No treatment i s required f o r some i n d u s t r i a l u s e s , e . g . f o r the h y d r a u l i c

t r a n s p o r t of s l a g o r coke cooling. Simple pretreatment, e . g .

mechanical, is

of ten s u f f i c i e n t f o r a considerable number of technological processes, e s p e c i a l l y f o r cooling, mining and h y d r a u l i c t r a n s p o r t . During t h i s p r e t r e a m e n t the cont e n t of iron Fe, manganese Mn and aluminium A 1 has t o be reduced. Pretreatment should include processes aimed a t removing ingredients which m y i n t e r f e r e with f u r t h e r water treatment processes. Water which comes i n t o d i r e c t c o n t a c t with the product by mining, benefic i a t i o n of o r e , t r a n s p o r t of ashes and coal , cleaning of gases e t c . , accepts p o l l u t i o n from the raw m a t e r i a l o r the intermediate product. I t has t o be t r e a t e d before the new cycle of use. Heterogeneous q u a l i t y requirements on water f o r processing, which a l s o depend on its t r a n s p o r t i n the p i p e l i n e system, o f t e n r e q u i r e the a p p l i c a t i o n of mu1 tigrade treatment technologies, including (a)

mechanical processes,

(b)

thermic processes ,

(c)

magnetic processes ,

154 (d) chemical processes, (e) biological processes. Chemical water treatment includes softening, decarbonization, deioniza t i o n , demineralization and other processes aimed a t decreasing the content of organic matter and dissolved oxygen, especially by using macromolecular ion exchangers. TABLE 2.24

Interference agents

Negative impact on

Iron (Fe) Manpanese ( h ) Humines

t a s t e and/or colour of tee, coffee, y e a s t , dough, m a l t , beer, milk, cheese, s t a r c h , sugar, tinned food ca t h a l y t i c d i s i n t e g r a t i o n of f a t s , reduction i n d u r a b i l i t y of food

~~

~

~ l c i u m / m f m eium s carbonate

tas t e / f l o c u l a tion of cacao t a s t e of b u t t e r , other milk products, and beer turbiditv/colour of alltoholic beverages, bottom sediments

(caw3 + MgC03)

Chlorides (C1-)

1)

t a s t e of coffee and tea

Natrium (Na) Hydrogencarbona t e

s t a b i l i t y of vitamins

Nitrates

production processes

Oxygen (02)

1)

Putrefactive and iron bacteria, mold fungi, dregs e t c .

oxidation of fats, decomposition of proteins (acce lera tion) negative impact on t a s t e , cause of health d i f f i c u l t i e s , disturbance i n production processes

Negative impact of selected agents on food products:

1) high content

Multigrade water treatment processes combine cheap processes f o r removing a s u b s t a n t i a l p a r t of the undesirable components with m r e expensive processes aimed a t achieving the desired q u a l i t y f o r a limited volume of water f o r cert a i n s i n g l e , s p e c i f i c process. The f i n a l product of this treatment is water of d i f f e r e n t q u a l i t i e s which is s u i t a b l e f o r c e r t a i n s p e c i f i c technological processes. During the use of water i n contact With the product and a s a cooling and heat carrying medium, i t is possible t h a t carbonates, o t h e r s a l t s , gases and organic matters may separate. I n t h i s way water is used during catching, cooling and cleaning of gases, extinguishing of coke etc. a l s o i n the food industry. The q u a l i t y requirements i n t h i s g o u p a r e complex and should correspond not only t o the previous ones, but a l s o to the requirements f o r cooling and h e a t carrying

155 matter. These requirements, which a r e p e c u l i a r t o each production process,

have t o be determined s e p a r a t e l y . For the p h a m c e u t i c a l and food industry drinking water is used and addit i o n a l q u a l i t y requirements applied f o r i n order to safeguard the appropriate standard of these products (Tab. 2 . 2 4 ) . 2.5.2 Cooling \*later Cooling water, which accepts and removes the excess h e a t during i n d u s t r i a l production, forms some 60-80% of the water quantity needed i n industry. This water undergoes t h e m 1 changes and o f t e n requires thennal treatment, including a l l the processes of water warming, cooling, d i s t i l l i n g , mixing with vapour and degasifying. Cooling by water i n contact with the semi-finished product a s c o n t a c t cooling i s a p a r t of processing. TABLE 2.25

Losses through

Requirements of cooling

\*later consumption ( l o s s e s )

Type of losses

water (m3.s - l ) Oncethrough sys tems

Ae - ce

R

(m3.s-l

. (T2 - T1) . R

Ae = 0.001. (T2-T1+10) .R

0.241. J

Open circuit SYs tern

Ae =

0.002.(T2-T1+13) .R

evapora t i o n Leakage evapora t ion wind ( c m c eimDact ntration)

T2 - T1 spreading, leakage, mud discharge

Closed circuit sys tern

evaporation (concentration) 1eaka ge mud discharge

Ae = 0.01.R

Losses through

J

I. wind impact 11. spreading

T

AI-Iv

=

C~-~”.R

T

111. leakage

I V . mud discharge (sludge)

- heat -

1

diverted (J.S-’) water inflow temperature

2- water outflow temperature (OC)

R

- cooling water requirements

Water requirements and l o s s e s i n d i f f e r e n t cooling s y s t e m . Water requirements i n once-through systems are permanent, i n c i r c u i t systems once per operation cycle. Systems f o r cooling without any c o n t a c t with the product a r e l i k e o t h e r ind u s t r i a l water systems, namely

(a)

open c i r c u i t sys tems,

156 (b) r e c y c l i n g sys tern - open, when the h e a t is removed by the d i r e c t c o n t a c t of water and a i r , - c l o s e d , when the h e a t is removed without any d i r e c t c o n t a c t with a i r , i . e . i n a closed h e a t exchanger. Cooling i s needed e.8. i n steam and nuclear power p l a n t s , during vapour condensation, bearing and o i l cooling, a s well as f o r the i n d i r e c t cooling of gases and l i q u i d s , furnaces, k i l n s e t c .

Water requirements depend primarily on the technological process and i t s -1 temperature, i . e . on the q u a n t i t y of h e a t J (J.s ) t o be removed and, secondly on the type of cooling system (Tab. 2.25, 2.26). They a r e s u b s t a n t i a l l y lower i n r e c y c l i n g systems . Closed systems prevent evaporation, thus f u r t h e r decreasing both water consumption and water requirements. Between 80 and 400'C

air

cooling is more advantageous than water cooling. TABLE 2.26

Cooli n p sys tern

Evaporation losses a t the a i r temperature

'0 C

10' C

20'

C

Losses through wind impact

30' C

Cooling towers n a t u r a l draught

- with

0.001-0.003

0.0010 0.0012 0.0014 0.0015

o.oo5

Outdoor s p r i n k l e r s

0.0020 0.0024 0.0028 0.0030

0.015-0.020

Cooling ponds and tanks

0.0007 0.0009 0.0011 0.0013

- a i r blmers

0

Water loss c o e f f i c i e n t s through wind impact cI evaporation ce and t h e i r dependence on a i r temperature and type of the system. The q u a l i t y requirements f o r water used a s a cooling mediim without any con-

t a c t with the product a r e derived i n such a way a s t o ensure the s a f e and e f f i c i e n t operation of t h e system (Tab. 2.27). They may be low f o r open c i r c u i t systems and must be high f o r recycling systems, preventing e s p e c i a l l y t h e i r corrosion and clogging. The q u a l i t y requirements f o r water used i n h e a t exchangers should s a f e w r d i t s t h e m s t a b i l i t y , i.e. eliminate the growth of biorrass, the s e p a r a t i o n of carbonates and o t h e r s a l t s and gases, e t c . , even under cond i t i o n s of multiple cycles of warming and cooling (Tab. 2.23).

A cumulation of the f o l l m i n g suspended mtter occurs i n t h e recycled water: ( a ) c r y s t a l s of s a l t s , e s p e c i a l l y of calcium carbonate CaC03 which a r e d i f f i c u l t t o dissolve, (b)

t h e prcducts of corrosion,

(c) microorganism, (d)

d u s t and s o o t ( e s p e c i a l l y i n open systems).

157 Cooling water has t o be t r e a t e d mechanically hy f i l t r a t i o n , by a l k a l i n e c l a r i f i c a t i o n , by ion exchangers, o r m ~ e t i c a l l y ,i n o r d e r t o decrease the sedimentation, e s p e c i a l l y of the calriwn carbonate. The sedimentation r a t e j n a closed system is e s s e n t i a l l y lower than i n an open system. TARLE 2.27

Velocity of water

Permissible c o n c e n t r a t i o n of p o l l u t i o n

flow (m.s-l)

Continuously

(0.01 0.01-0.2 0.2-0.5

c 5

(me.1-l)

Short-term

< 20

- 20

50

30 - 50

100

10

Permissible c o n c e n t r a t i o n of p o l l u t i o n i n c o o l i n g water and i t s dependence on the c o o l i n g water f l m v e l o c i t y . For the treatment of water f o r c o o l i n g , i t is necessary t o remove organic components, which a r e a b l e t o form porous d e p o s i t s i n a warm environment, thus clogging t h e c r o s s p r o f i l e o f the p i p e l i n e system, i n c r e a s i n g t h e f l a g r a t e and decreasing i t s h e a t c o n d u c t i v i t y . I n the closed c i r c u i t r e c y c l i n g system i t is n o t necessary t o rernove the i n f e c t i o u s b a c t e r i a : t h i s i s only indispensable when the water comes i n t o d i r e c t c o n t a c t w i t h t h e product o r w i t h t h e s t a f f i n some i n d u s t r i a l branches, e s p e c i a l l y i n the food and pharmaceutical i n d u s t r i e s . B o i l i n g and Stream Power h'ater 2.5.3 Roiling water is used as a h e a t c a r r y i n g medium without any c o n t a c t with the and undergoes s i m i l a r changes a s c o o l i n g water. B c i l i n g mmter and steam d u r i n g processing, f o r h e a t i n g and v e n t i l a t i o n , f o r power g e n e r a t i o n , as warm service w a t e r . The temperature of water i n t h e supply network of warm water systems general l y depends on the energy i n p u t and o f t e n reaches 150OC. Temperatures not exceeding 100°C are a d m i s s i b l e i n networks whose o u t p u t does n o t exceed 1 . 7 G J per hour. IJam water f o r i n d u s t r i a l purposes is seldom supplied by t h e municipal supply s y s tem. ' h e water q u a l i t y requirements follcw

-

the decrease i n corrosion the decrease i n clogging. Corrosion is supported by f r e e CQ2,

low pH f a c t o r ( < 8 ) , iron Fe and copper

Cu c o n t e n t , and by a h i g h e r Oxygen c o n t e n t ( > 0,OZ mg 02. 1-l).

Clogging is

158 caused rrainly by CaC03, MgCQ3,

€i2Si03, sediments, organic colloids and o i l .

The quantity of water i n power generating systems is formed by feed water t o f i l l the system and supplementary water to cover water losses, caused especially by leakage and evaporation: Vo = R f + R s

Vo

-

-

/Ad,

n

volume of water i n the recycling system

Rf - feed water (for the f i r s t f i l l i n g up) Rs

-

A

- water

t

-

(m3

(m3 .s -1)

losses

(s)

time

-

(m')

<m3 )

supplementary water

After the f i r s t f i l l i n g of the system Vo Rs

(2.86)

(m3)

Jddt

=

Rf and, therefore, (2.87)

(m3)

Total water requirements, corresponding t o the water withdrawal, a r e W

= Rf

+

(2.88)

Rs

?he q u a l i t y requirements of the feed and supplementary water should also safeguard its t h e m s t a b i l i t y , limiting the content of suspended m t t e r , o i l and chemically aggressive components t o almost n i l . Such water should be c l e a r and without any colour. The t o t a l content of ions is limited t o 10-14 mn01.1-~, ions of calcium Ca2+ and t o t a l carbon dioxide C02 t o l e s s than 3 . 6

- 7.0

ml.l-'. h e r values correspond t o the density of the energy output above

23 kW.m-2 (Tab. 2.28). The content of gases and organic m t t e r i n condensed steam depends on the nominal pressure and on the thermal scheme of the system

-

i t exceeds the water

content. The feed water of these systems i s a mixture of the returned condensed steam and the supplementary water

.

Methods of t r e a t i n g the condensed steam include f i l t r a t i o n , demineraliza tion and deoxygenation. Steam treatment i n heating plants and pcwer plants often includes the softening and removal of organic matter and o i l . Steam systems have to be protected from the aggressivity of water by m i n t a i n i n g the protect i v e a l k a l i n i t y , which can be achieved by dosing s o l i d o r v o l a t i l e deoxigenation

or other agents. This protection can a l s o be achieved under a neutral regimen by the removal of corrosive gases, s a l t s and other aggressive p a r t i c l e s , i . e .

by the treatment of the condensed steam and by the demineralization of the supplementary water.

159 TABLE 2.28

W

bi C

"

X

m a r

\dater q u a l i t y indicator

0

!i

w

.r

i

rou0l.l

-1

fig.1-l

c2

15 15 50

50

15 1.5

50 500 100 20

Fe

mg. 1-1 pcg. 1-1

1 20

cu

f i g . 1-1

5

0.25 2.5 1 . 5 1 0.5 10 20 10 10 ZC 0.5 5 20 30 5 1

C k i d i z a b i l i t y CODFln'mg 02.1-l Swpended matter Specific e l e c t r i c a l conductivity S i02

103

9'

9'

13'

-

50

50

5 2 50

0.3

10' 0.5

ps cm-l &. 1-1

20

20

p-apparent a l k a l i n i t y rran0l1-l Surplus of P20 5 Oil

0.5 0.5 20 20

1 0 5 5 5 3 2

50

g.1-l

1 20

mg.1

-1

-1

mg. 1

6'

2.5' 0.6'0.3' 0.05-1.5 < 0.05 2-10

3

3

3

1-3 0.5-2 0.3-1

3

Water q u a l i t y i n d i c a t o r s f o r feed and b o i l e r water (+) depend on the type and o u t p u t of the thermal economic system. Heated water and steam form a medium which enables the transformation of chemical and nuclear energy i n t o e l e c t r i c a l energy i n thermal and nuclear p m e r p l a n t s . According t o Minasian e t a l . (1977), t h e water requirements reach

-

i n a t h e m 1 p w e r plant i n h e a t and power p l a n t s i n nuclear power p l a n t s

A t present 0.127

i n 2000 0.104 m3 .ldnl-l

0.101

O.C.50

rn3.k1h-'

0.200

0.125

m3 .kWh-l

The r a t i o of water consumption i n t h i s case reaches 0.01 t o 0.02. Davis and Wood (1974) estimate water consumption during power generation a t 10 km3yearly

"he water demand f o r t h i s purpose i n developed countries is gradually reaching

160 the water demand f o r i r r i g a t i o n . Rut the use of water for power generation purposes is not a s consumptive. Water Losses i n Industry and F l a g Chart of Water Ike

2.5.4

Because of the prevailing percentage of water used for cooling purposes, the prevailing losses of water i n industry a r e formed by Percentane of the volume of water used

(a)

evaporation

(b)

(c)

escape and spreading leakage and leaching

(d)

mud discharge

c(O/O)

(Ole)

5

1.5 X 0.L-0.8 % 1 - 2 % up to

87 6 5 4% 3.5 3%

6 %.

2.5%

ne

2 O/O

4

3

2 I

0I

1.8

02

2.6

3.4

Aes+

Fig. 2.16. I n t e r r e l a t i o n s of evaporation, spreading and wind action losses and of the concentration of s a l t s i n a water cooling system: e - evaporation, es - spreading and cscape, s - Sludge, c - concentration of s a l t s . The prevailing losses a r e those caused by evaporation. They depend not only on the type of the system and i t s equipment, but a l s o on the method of i t s operation. Minimum losses can be achieved i n closed recycling systems by uninterrup ted opera tion. Losses through evaporation and corrosion cause the concent r a t i o n of s a l t s which may exceed the relevant mximm permissible values i n the recycling system

(Fig. 2.16). This concentration is defined by the f o l l w

ing conceGtration r a t i o ( f o r a ccoling or s i m i l a r system)

fA i

c

=

9 i=l

j

A1

- losses

*2

-

losses throuFzh spreading

A3

-

evaporation losses

through escape

(2.89)

161 Losses through w a t e r escape may a r i s e i n open systems only when the a i r flow takes away droplets and carries them outside the cooling system. The value of this loss depends on the a i r flow r a t e , i , e . on the gradient of temperatures and the type of system. Losses through spreading a r i s e as a r e s u l t of the influence of wind, i . e . again i n open systems only. The value of t h i s loss depends on the construction of the spray cooler and on the velocity of the wind. I t s value is not constant and, therefore, cannot be replaced by an estimated average. Unproductive leakage m y not only a r i s e i n cooling systems, but a l s o in lagoons, oxidation ponds e t c . , i . e . a f t e r processing. They do not necessarily increase the relevant water requirement. Their values reach a maximum a f t e r the f i r s t f i l l i n g up of the reservoir and then gradually decrease due to clogging. Losses during water purification or waste water treatment a r e caused by using water as a medium f o r collecting waste material and sludge. They occur periodically o r permanently, depending on:

w

-

t

- the time period of t h e i r accumulation

N

=

m

the volume of removed waste material the moisture content of the waste m t e r i a l

N . w t 100

(m3 (%) (s)

(m3.s-')

.

(2.90)

Water consumption and mud discharge water i n a recycling system has to be replaced by supplementary water Rs

F,

- mud

U1-3-

3 -1)

discharge water, replaced f o r improving water q u a l i t y

(m .s

consunptive use by a product, by-product and by means of wastes

(m3.s-l)

The function of i n d u s t r i a l water supply and disposal systems using water i n contact or without any contact with the product can be analyzed by means of modelling. The model using water without any contact with the product includes e.g. a spray cooler, treatment plants f o r the recycled and feed water and f o r mud discharge. Inputs of such a model include (Fig. 2.17) feed (supplementary) water, characterized by

-

Ro

-

co

- concentration of d i s s o l w d - water temperature

To

discharge

(m3.s-l) solids

(mg.1-9 ("C)

162

-

l i q u i d and s o l i d p a r t i c l e s entering the system from the a i r characterized i n

the same way, Qa, ca, Ta -

t h e m 1 energy: J,

Jar . , J

(J)

~TARYWATEF

Fig. 2.17. Simple model of water usage i n industry with m e water recycling and one water re-use c i r c u i t , i l l u s t r a t i n g the balance of water q u a n t i t i e s , of the diluted and suspended r a t t e r and of the energy input and output. Inputs i n a system using water i n contact with the product include, i n addition to this, liquid and s o l i d p a r t i c l e s entering the system from the raw material and

-

semi-finished product (Qm, G, T ~ ) Outputs of a model of i n d u s t r i a l water supply and disposal system without any contact w i t h the product include:

-

waste water, characterized by

R8 - discharge

- concentration of dissolved T8 - water temperature c8

-

(m3, s-l) solids

(w.1-5 ("C 1

mud discharge (from the treatment of the recycled water, sludge treatment

etc.)

- water

-

losses through evaporation Ae, escape and spreadingAes losses of energy (e.g. by evaporation Je>

163 Outputs i n a system using water i n c o n t a c t with the product include, i n a d d i t i o n to t h i s ,

-

consumptive use u1 , IT2 , [I3. IJsing such a model, the balance (a) (b)

of the water q u a n t i t i e s (water d e l i v e r y , r e c y c l i n g and d i s p o s a l ) , of the d i l u t e d and suspended matter

( c ) of energy i n p u t and output can be analyzed i n d i f f e r e n t p a r t s of the system. (a) The volume o r discharge of t h e supplementary water can be determined on the b a s i s of the balance

(2.92)

(m3. s - l )

Apart from the supplementary water R1 the recycled water R7 and re-used water R

5

also e n t e r the subsystem, thus

The o u t f a l l from the i n d u s t r i a l water system is the waste water R

8

=

R3

- R5

(2.94)

(m3.8)

-Ao2

and mud discharge

N = A01.'01 (b)

+A02'c02

+

(2.95)

A03'C03

The chemical balance can be analyzed by equations of the following type

R2.c2 = R 3 .c3 + R 6' c 6 +

*. c i

+ Q,c,,

+

Qaca

(2.96)

The water q u a l i t y i n the system changes a s a r e s u l t of the i n p u t of energy and matter. I n the case of a cooling system (U = 0), the r a t e of d i s i n t e 112 ?3 g r a t i o n , caused by d i f f e r e n t chemical and biochemical processes r e s u l t i n g i n changes i n water q u a l i t y , depends on t h e discharge t o w l u n e r a t i o i n the cooling p l a n t . This can be expressed by a d i f f e r e n t i a l equation

(2.97) c.

-

concentration of t h e water q u a l i t y i n d i c a t o r i (mg.1 -1 )

V

-

volume of water i n the system

164 The r a t e of concentration changes i n the canponent i depends on the o r i g i n a l maximum concentration ci(o, a t the moment to (2.98)

The trouble-free operation of an i n d u s t r i a l water supply, and re-cycling and d i s p o s a l , system requires a s t a b l e water q u a l i t y , which should be m i n t a i n e d by - a s o p h i s t i c a t e d water recycling and re-use system

-

a p p r o p r i a t e d e l i v e r y of the supplementary water maintenance of water q u a l i t y by an appropriate dosage of relevant chemical

substances . The dose of the chemical substance to maintain i t s required concentration ( t o p r o t e c t the water supply and recycling system o r t o maintain the q u a l i t y required f o r processing) i s , t h e r e f o r e , (2.99)

The influence of water l o s s e s on water q u a l i t y d i f f e r s : evaporation losses change the concentration of most water q u a l i t y i n d i c a t o r s , while seepage, escape and spreading do n o t . To maintain the required water q u a l i t y , the necessary input of the supplementary water is t o be derived from evaporation losses

A,

and

t h e d i f f e r e n c e s i n the i n p u t and output concentration C,

R1 = Ae

3 . c -c

(2.100)

3 2

When the water treatment p l a n t of both the supplementary and the recycled water a r e a b l e t o maintain a constant water q u a l i t y , the changes i n concentrat i o n depend mainly on t h e evaporation r a t e and on the matter input from the

water re-use c i r c u i t . The q u a l i t y of water t h a t can be recycled depends on the permissible concentration of t h e suspended matter and on the e f f i c i e n c y of f i l t r a t i o n i n the treatment p l a n t of the recycled water. High e f f i c i e n c y of f i l t r a t i o n helps t o increase the r a t i o of the recycled water R

f 6 =

R3+4?s f

-

?2

(2.101)

e f f i c i e n c y of f i l t r a t i o n

( c ) The water temperature i n d i f f e r e n t p a r t s of the system and the temperat u r e of the waste water can be determined from d i f f e r e n t equations of the e n e r *tic balance, e.g.

165 J

n = J o + J p - X A J i + aJ + Jm 8 i=l

(2.102)

(J.S-')

Water recycling and re-use r e q u i r e higher funds to be a l l o c a t e d by the user f o r the investment, enabling him t o make savings i n operation c o s t s . The applic a t i o n of these technologies r e s u l t s i n a reduction of water withdrawals with a subsequent improvement of water balances and of the water q u a l i t y i n surface and groundwater resources. Was te Waters and Mas te-free Technologies 2.5.5 Idas te water which is discharged i n t o streams c o n s t i t u t e s an ever-increasing proportion of water supply. With regard t o the s e l f - p u r i f i c a t i o n and water treatment process, the r e l e v a n t waste p a r t i c l e s can be considered a s (a)

b i o l o g i c a l l y degradable,

(b)

b i o l o g i c a l l y undegradable.

I n e f f e c t , the contamination caused by i n d u s t r i a l waters can be categorized as ( a ) chemical - d i l u t e d and suspended chemicals, (b) b i o l o g i c a l - b a c t e r i a , viruses and o t h e r pathogenic organisms, ( c ) thermal. I n d u s t r i a l waste waters a r e generally mixed. The contamination is mostly t o x i c ; but the harmfulness OE the wastes depends not only on t h e i r t o x i c i t y , but a l s o on t h e i r a b i l i t y t o slow down o r t o s t o p t h e processes of s e l f - p u r i f i c a t i o n i n r i v e r s , o r of b i o l o g i c a l water treatment i n r e l e v a n t p l a n t s . TABLE 2.29

Waste water groups Cooling Mining and hydraulic transport

F_

Origin

S u i t a b i l i t y f o r r e - u s e and re-cyc 1ing

cooling systems

good, occasionally without s p e c i f i c

lagoons, s e t t l i n g tanks

good, simple treatment technologies

q u a l i t y depends on raw m a t e r i a l and technology applied

generally demanding treatment technologies : food.~.paper and pulp industry' waste waters s u i t a b l e f o r irrigation; possibilities for material recoven

F,LLL

Processing incl. rinsing 'F

P Sewage Other waste wa terS

F R Fb

1

not s u i t a b l e f o r i n d u s t r i a l re-use, suitable for irrigation feed,yter? precipitation

n o t s u i d b l e , a c c i d e n t a l occurrence, requires a c c m u l a t i o n

C l a s s i f i c a t i o n of i n d u s t r i a l waste waters with regard t o p o s s i b i l i t i e s of t h e i r re-use and re-cycling. See Fig. 2.15.

166 ?he p o s s i b i l i t i e s of waste water re--use o r recycling depend on the q u a l i t y of the waste waters concerned, i . e . on t h e i r o r i g i n and on the type of the ind u s t r i a l process (Tab. 2 . 2 9 ) . The o u t f a l l of the system is treated waste water: (m3.3) This quantity, o r p a r t of i t can be re-used,

(2.103)

thus decreasing the quantity of

waste waters discharged i n t o water resources (Fig. 2.15) :

FA

= Fo

.f? i = f Ai

- Rw

(2.104)

(x3.s-1)

Data on the chemical and biological composition of waste waters can be derived by an analysis of the relevant technological processes on the basis of the material balance. The degree of pollution of i n d u s t r i a l waste waters can be compared with domestic sewage by means of population equivalent values. The population equivalent value of i n d u s t r i a l pollution corresponds to the number of inhabitants producing pollution whose biological oxygen demand BOD has the same

5

value a s waste waters frcm the relevant i n d u s t r i a l production processes. This population equivalent value E can be r e l a t e d t o the d a i l y production o r to the production mi t :

3

E =

ROD5(g.m )

54 F:

.

3

Q(m )

(per u n i t of production, per day)

(2.105)

The sewerage system normally discharges d i f f e r e n t kinds of sewage water, or discharges d i f f e r e n t types of sewage waters separately. Nevertheless i t is necessary t o prevent the penetration of aggressive substances i n t o the sewerage system, o r to prevent the penetration of waters containing (a) matter which destroys sewerage s t r u c t u r e s or damages the materials of the sewerage system, (b)

m t t e r which causes breakdowns i n the waste water treatment processes.

(c) matter which is infectious, contaiminated, poisonous , narcotic o r radioa c t i v e t o such a degree t h a t i t threatens the health of the s t a f f i n the treatment plant or of the population, o r forms these substances i n admixture with waste waters from other processes

,

(d) explosive o r combustible substances, o r ccmpounds which form such substances with water o r a i r o r other substances which can penetrate i n t o the Sys tern , ( e ) substances with a n extremely offensive odour o r which cause such an odour i n admixture with waste waters from other production processes. These waters a r e a l s o n o t s u i t a b l e f o r re-use or recycling. The penetration of waste waters i n t o water resources leads to a d e t e r i o r a t i o n i n t h e i r q u a l i t y , a s w ~ l al s i n the qimlity of the o t h e r compounds of the biosphere.

167

Output data: Water withdrawals

w

Water consumption C

Final effluent F ( waste load N ) Waste water quality q, - q,

Water rates MI-Ms Penalties etc P4-P4

R,C,N,r- f 4 - 4 ( A , B , C,D, E , M I - 6 Investment and operation casts.

Fig. 2 . 1 8 . Block diagram f o r the determination of water requirements and m ~ g e ment of water deliveries as w e l l a s waste water disposal i n industry in accordance with the hierarchy of goals and the basic limitations. In order t o reduce the negative impact on future development, the u t i l i z a t i o n of water i n industry should be ratio&lized, especially by means of the f o l l o w ing wa ter-saving measures (Fig. 2.18) : (a) reducing water wastage, (b) limiting the duration of water u t i l i z a t i o n during technological processes to the absolute minimum,

(c) selecting processes which e n t a i l minimum water consunption and minimum Water pollution, (d) applying internal recycling and waste water re-we,

168

(e) decreasing the requirements on water quality t o the technologically permissible l i m i t and by using available resources of low quality, ( f ) using industrial waste waters i n other branches of the national economy, especially i n agriculture. A decrease i n the volume of wastes i n industrial production can be achieved bY

-

a change of technological processes, a change of product mix, enabling the u t i l i z a t i o n of waste material as raw

material f o r other products, - a reduction i n the weight of products - water recycling and waste water re-use,

-

using selected waste nlaterial a s f e r t i l i z e r s i n agriculture. Liquid, s o l i d and gazeous wastes a r e often suitable as raw material f o r other production processes,

for m t e r i a l reiovery, f o r s o i l regeneration, - for power generation. -

These problems a r e interdisciplinary, having an impact not only on water management, but a l s o on the biogeochemical cycles and the exhaustion of the natural resources. To moderate t h i s problem, the production processes should be gradually, as f a r as possible, incorporated i n t o natural biogeochemical cycles. Production processes which a r e aimed a t the maximum u t i l i z a t i o n of a l l raw materials on the one hand and a t the re-use of material products a f t e r t h e i r u t i l i z a t i o n on the other hand gradually lead t o waste-free technologies. Their introduction requires the variety of products and the system of t h e i r u t i l i z a tion t o be changed, i n order t o enable t h e i r return into the production cycle o r t h e i r unexceptional coalescence with the environment. This goal can partly be achieved by the higher service l i f e of products, i f t h e i r repair is economically feasible. The issue of energy consumption i s also interconnected with these problems, because power generation likewise leads t o the over-utilization

of available natural resources and t o environmental pollution (Fig. 2.19). The necessary reorganization of production can be achieved by grouping relevant production processes i n t o integrated schemes. I n such a way i t is possible t o apply continuous technologies , which may be financially less feasible, but r e s t r i c t the negative impact on the environment. But there are limits t o production concentration. A high concentration, even i n the case of a low production of wastes per product, causes such a high concentration of waste material and waste waters t h a t t h i s cannot be locally a d economically disposed of without harmful effects on the environment. The step-by-step introduction of waste-free technologies requires a systema-

169

Fig. 2.19. Schematic r e p r e s e n t a t i o n of t h e conventional n a t u r a l resourcesdemanding production and consumption process which leads t o accumulation of wastes (black arrows) and t o an excessive environmental p o l l u t i o n . IJnconventional waste-free technologies (hatched arrows) decrease t h e environmental p o l l u t i o n a n d t h e n a t u r a l resources exhaustion. t i c approach, which must consider a l l t h e s c i e n t i f i c , t e c h n i c a l , economic, s t r u c t i i r a l and s o c i a l a s p e c t s of human development: i n d u s t r i a l production, t r a n s p o r t and power g e n e r a t i o n , covering t h e sphere of a l l u s e r s : i n s h o r t , the everyday l i f e o f a l l i n h a b i t a n t s . The t r a n s i t i o n t o t h i s p r o s p e c t i v e technoloey

i s a n i n t e g r a t e d and gradual process aimed a t c l o s i n g the c i r c l e between t h e sphere of production and t h e sphere of u s e r s . 2.6

WATER I N AGRICULTITRAL SYSTENS

A g r i c u l t u r a l production is a r e s u l t of the f u n c t i o n of a g r i c u l t u r a l systems and has t o be managed w i t h i n t h e i r framework. An a g r i c u l t u r a l system can be defined as a s e t of interconnected s o i l and m i c r o b i o l o g i c a l , p l a n t , mechanical and human elements whose i n t e r a c t i o n produces o r g a n i c matter f o r t h e nourishment of man on t h e b a s i s of t h e supply of s o l a r , mechanical and human energy and matter i n c l u d i n g water, f e r t i l i z e r s and agrochemicals (Fig. 2.20). This system can also be expressed a s t h e i n t e r s e c t i o n of p l a n t ecosystems, t h e microbiolog i c a l system of s o i l and t h e l i v e s t o c k breeding a s w e l l a s agrochemical producing system AS = PE n MS n LA AS - a g r i c u l t u r a l system

(2.106)

170

PE - p l a n t ecosystems MS - microbiological system of s o i l

LA - l i v e s t o c k breeding and agrochemical producing system

VESTOC

Fig. 2.20. A g r i c u l t u r a l system, i t s environment and b a s i c i n t e r r e l a t i o n s h i p s of i t s subsystems (microbiological s o i l system, p l a n t ecosystem, l i v e s t o c k breeding system). Basic inputs (energy and labour, sediments and f a l l - o u t , f e r t i l i z e r s and p e s t i c i d e s ) and outputs ( p l a n t and a n i m l products, eroded and leached material).

The process of the accumulation and transformation of s o l a r , mechanical and human energy and matter takes place e s p e c i a l l y on t h e a c t i v e s u r f a c e of s o i l minerals, i n t h e i r microbiological communities, i n the r o o t s , stems, leaves and f r u i t s of p l a n t s and i n the d i g e s t i v e organs of l i v e s t o c k . Plant ecosystems transform s o l a r energy, water and nutriments i n t o organic matter. This p l a n t

matter, decomposed e s p e c i a l l y by t h e d i g e s t i v e organs of p o l y g a s t r i c l i v e s t o c k , is transformed i n t o mre complicated p r o t e i n s , sacharides and animal f a t . Waste matter which has not been incorporated i n t o t h e r e s u l t i n g animal matter contains mainly carbon and nitrogen. I t r e t u r n s i n t o t h e s o i l i n the form of manure, d u n p a t e r e t c . and i s subseqiiently transformed i n t o polymolecular rratter, o r humus, by t h e microbiological communities i n s o i l . This process regenerates t h e bioenergetic p o t e n t i a l of the s o i l , which depends on t h e e x t e n t of the a c t i v e surfaces and t h e s t r u c t u r e of the s o i l compo-

171 nents and may be c h a r a c t e r i z e d as

E = - t Y

(2.107)

XN I Y - dry wei&t o f y i e l d I N - weight of main n u t r i e n t s ( n i t r o g e n N , phosphorus P , potassium K)

(t) (t)

The s t a b i l i t y o f t h e a g r i c u l t u r a l system and t h e permanent course of t h e a g r i c u l t u r a l prodiiction process depend on t h e equilibrium of t h e r e l e v a n t s o i l , p l a n t and animal subsystems and on t h e equilibrium of t h e a g r i c u l t u r a l system and i t s environment w i t h i n t h e framework of t h e n a t u r a l hiogeochernical cycles: Basic i n p u t f a c t o r s , i . e . energy, water and l a b o u r , must safeguard a permanent and s u f f i c i e n t supply of r e l e v a n t matter from one subsystem t o another. I n the case of an i n s u f f i c i m t o r i n t e r r u p t e d supply, t h e system becomes u n s t a b l e and can e n t e r a n u n c o n t r o l l a b l e s t a t e .

Two o f t h e e x i s t i n g feedbacks i n an a g r i c u l t u r a l system a r e p a r t i c u l a r l y important and r e g e n e r a t e t h e b i o e n e r g e t i c p o t e n t i a l E PE

-

(2.108)

MS

(2.109)

IA-MS-PE-IA

The a g r i c u l t u r a l production gradually t a k e s away, f o r t h e sake o f hunlan s o c i e t y , a c e r t a i n a m u n t of m a t t e r i n t h e form of p l a n t and animal products, thus destroyinq t h e n a t u r a l balance. Where t h i s production i s very i n t e n s e , t h e missing matter is not s u f f i c i e n t l y replaced by the biogeochemical c y c l e s . It h a s , t h e r e f o r e , t o be replaced a r t i f i c i a l l y , by means o f f e r t i l i z e r s and i r r i g a tion.

A p o s i t i v e biogeochemical development o f t h e t e r r i t o r y sets i n whenever the functions of t h e a p - i c d t u r a l system g r a d u a l l y b r i n g mre and more m a t t e r i n t o the hiogeochernical c y c l e s . This p r o c e s s , which r e s u l t s i n a n extension of t h e b i o l o g i c a l p r o d u c t i v i t y of t h e t e r r i t o r y , can be achieved (a)

extensively

-

by t h e extension of a g r i c u l t u r a l l a n d ,

(b) i n t e n s i v e l y - by t h e i n t e n s i f i c a t i o n of t h e a g r i c u l t u r a l and agroi n d u s t r i a l p r o c e s s e s , i . e . by a n increased i n p u t of energy and m a t t e r , e s p e c i a l l y

water, f e r t i l i z e r s and forage. A g r i c u l t u r a l water requirements a r e frequently s a t i s f i e d by a combination of on-site and e x t e r n a l s u p p l i e s . The r e g u l a t i n g f u n c t i o n of water has t o be achieved by a n e x t e r n a l w a t e r supply f o r (a) (b)

r e g u l a t i n g t h e s o i l moisture by means of i r r i g a t i o n and drainage,

(c)

f i s h and w a t e r p o u l t r y breeding,

l i v e s t o c k and p o u l t r y breeding,

172 td)

p r o c e s s i n g , b o i l i n g , c o o l i n g , h e a t i n g , waste d i s p o s a l ,

(e)

p u b l i c uses i n a g r i c u l t u r a l s e t t l e m e n t s .

A g r i c u l t u r a l Production and A g r i c u l t u r a l Y i e l d 2.6.1 The subsystem of t h e l i t h o s p h e r e and atmosphere where p l a n t prodiiction takes p l a c e includes (a)

2 - 4m deep and, e x c e p t i o n a l l y , deepcr s o i l l a y e r with t h e r o o t svsteni

and microbiolopical communities, ( b ) 2 - 6rn high and, e x c e p t i o n a l l y , h i g h e r l a y e r of t h e atmosphere containi n g t h e upper p a r t of t h e p l a n t s . Present-day a g r i c u l t u r a l production i s becoming a m r e and iinre complicatpd process with i n d u s t r i a l c h a r a c t e r , which h a s , i n t e r a l i a f o r economic reasons, to t a k e rnaxinium advantag? of n a t u r a l f a c t o r s and must n o t be allowed t o adversely a f f e c t t h e environment. The a g r i c u l t t i r a l y i e l d i n a given a r e a is a function of eight factors

Y =

Y - yield

s -

s o i l t y p e , i t s t e x t u r e and s t r u c t u r s , i t s water holdinE capacity ( r p l a t i v e ly stable)

w - weather,

siipply of energy and water ( v a r i a b l e , c o n t r o l l a b l e onlv i n hot-

houses)

c -

q u a l i t y and s u i t a b i l i t y of p l a n t s and t h e i r seeds ( c o n t r o l l a b l e i n advance’,

F - q u a l i t y and s u i t a b i l i t y of f e r t i l i z e r s ( c o n t r o l l a b l e i n advance) M - machinery and i t s proper i i t i l i z a t i o n ( o p e r a t i v e l y controllable’,

H - human labour ( o p e r a t i v e l v c o n t r o l l a b l e ) 0

- water supply and i t s a p p r o p r i a t e timing, water q u a l i t y and a p p r o p r i a t e irrigation practices. Veather and s o i l , s t a b l e w i t h i n the framework o f crop r o t a t i o n c y c l e s , a r e

key f a c t o r s i n t h i s equation. The o t h e r f a c t o r s , e s p e c i a l l y t h e s e c o n t r o l l a b l e i n advance, have t o be adapted t o t h e i r c h a r a c t e r i s t i c s . Operatively c o n t r o l l a b l e f a c t o r s have t o be nunaged with p a r t i c u l a r regard t o t h e weather, which is a v a r i a b l e and u n c o n t r o l l a b l e f a c t o r . The e x p l o i t a t i o n of s o i l and water demand c l o s e l y depends on both these key f a c t o r s . F e r t i l e s o i l s g e n e r a l l y have h i g h e r water requirements per h e c t a r e of l a n d , p e r m i t t i n g h i g h e r s p e c i f i c y i e l d s t o be achieved ( t p e r h e c t a r e ) . T h e i r s p e c i f i c water demand p e r u n i t of product (m 3 p e r t ) i s , t h e r e f o r e , a b s o l u t e l y lower. These s o i l s permit t h e achievement of h i g h e r y i e l d s with a lower dose of f e r t i l i z e r s (Fig. 2 . 2 1 ) . IJnder t h e conditions of a wanner c l i m a t e , evapotransp i r a t i o n i s more i n t e n s i v e due t o t h e h i g h e r i n p u t of s o l a r energy. R e s u l t i n g y i e l d s a r e h i g h e r a s f a r as r e l e v a n t h i g h e r water requirements a r e s a t i s f i e d .

173

yield

r

I

I

I

I

90

150

1

( t . ha’)

I

0

30

1

210

(kg)N

Fig. 2.21. I n t e r r e l a t i o n s of y i e l d , s o i l q u a l i t y and t h e q u a n t i t y of f e r t i l i z e r s according t o RuliCek ( 1 976) : h i g h e r y i e l d s are achieved by lower f e r t i l i z i n g r a t e s under b e t t e r s o i l c o n d i t i o n s (a - medium q u a l i t y s o i l , b - high q u a l i t y s o i l ) . An i n c r e a s e i n f e r t i l i z i n g r a t e s above t h e optimum value increases water resources contamination, thus reducinp both t h e y i e l d and economic e f f i c i e n c y . Tne water requirements Ra of p l a n t s a r e p r i m a r i l y c o n t r o l l e d by t h e p r e v a i l ing weather and a l s o depend on t h e s o i l conditions when water supply is iinlimited. T r a n s p i r a t i o n i s p r o p o r t i o n a l t o r a d i a t i c n and can be q u a n t i t a t i v e l y a s s e s s e d from t h e r e l e v a n t weather elements. The w a t e r requirements Ra c o n s i s t - of t h e t r a n s p i r a t i o n T of t h e p h y s i o l o g i c a l l y a c t i v e p l a n t and

- of t h e evaporation E R~ k

=

T

+ E

-ke.

from t h e a d j o i n i n g s o i l s u r f a c e T

(m3. ha-’ )

(2.111)

- s o i l q u a l i t y c o e f f i c i e n t , a l s o depending on a g r i c u l t u r a l p r a c t i c e s , overshadowing, the presence of weeds, g e n e r a l l y ke = 1.2 - 1.5. The growth of p l a n t s i n terms of n e t a s s i m i l a t i o n or dry-matter increment,

a l s o depends on t h e energy i n p u t , b u t does n o t commence u n t i l r a d i a t i o n reaches a c e r t a i n minimum i n t e n s i t y . I t reaches a maximum rate a t moderate r a d i a t i o n i n t e n s i t i e s , i n c r e a s i n g only a l i t t l e a t high i n t e n s i t i e s . Y e t y i e l d does n o t only depend on a s u f f i c i m t and adequate supply of energv

and w a t e r , b u t a l s o on a s u f f i c i e n t supply o f a i r t o t h e r o o t zone. This f a c t

i s expressed by t h e i n t e r p l a y of t h e f a c t o r s S - s o i l q u a l i t y and Q - water supply - of t h e v i e l d equation (Eq. 2.110). llnder e f f i c i e n t a g r i c u l t u r a l pract i c e s the amount o f water slipplied corresponds t o t h e a c t u a l e v a p o t r a n s p i r a t i o n ; l o s s e s are n e g l i g i b l e . Water consumption i s alrnos t equal t o water requirements. I r r i g a t i o n is an i n h e r e n t l y consumptive w e , l a r g e l y reducing t h e p o s s i b i l i t i e s f o r t h e m u l t i p l e u t i l i z a t i o n o f water. Maximum y i e l d s can be achieved under s o i l moisture conditions of t h e f i e l d c a p a c i t y FC. When t h e value of humidity i s h i g h e r , t h e a e r a t i o n i s i n s u f f i c i e n t . I n heavy s o i l s , t h e a e r a t i o n i s a l r e a d y i n s u f f i c i e n t i n t h e conditions of t h e

174 f i e l d capacitv, thirs decreasing y i e l d s considerably. The s i z e of the pores is too small t o enable the necessary degree of a e r a t i o n . Light s o i l s a r e f a r more t o l e r a n t t o an increase i n s o i l humidity above t h e limits of the f i e l d capacity. The s i z e of the pores enables a s u f f i c i e n t supply of both water and a i r (Fig. 2.22). yield ( t . ha’)

I

3

2

4

Fig. 2 . 2 2 . I n t e r r e l a t i o n s of y i e l d , s o i l humidity (expressed a s the s u c t i o n pres s u r e pF), and s o i l type according t o Kutilek (1963): ( a ) sandy s o i l s form b e t t e r conditions f o r achieving higher y i e l d s a t lower s o i l humidity due t o the b e t t e r a e r a t i o n , i . e . t h e same y i e l d i s achieved with lower water requirements. - Ib) heavy clayey s o i l s . The maintenance of t h e moisture capacity between t h e l i m i t s of t h e f i e l d capacity under t h e v a r i a b l e conditions oE weather e s p e c i a l l y of uneven precipit a t i o n and evaporation, has t o be achieved not only by i r r i g a t i o n , but a l s o by drainage. Yields depend on the maintenance of adequate s o i l moisture l e v e l s duri n g the various s t a g e s of p l a n t growth. The water requirements of p l a n t s depend ( a ) on the i n t e r p l a y of the t r a n s p i r a t i o n r a t e and the supply of water from the root zone, i . e . on t h e r e s i s t a n c e of the p l a n t body t o the penetration of water from t h e s o i l t o the atmosphere, f b ) on the a c c e s s i b i l i t y of t h e s o i l p r o f i l e t o water, depending on the development o f the r o o t system, f c ) on t h e evapotranspiration r a t e , depending on weather conditions. The water reqi;irements of p l a n t s R,

and t h e i r consumptivr! use T I a r e a com-

bined function Ra = lJa

=

f (S

,

C

, A , IJ)

3 -1 (m .s )

(2.112)

S

-

C

- p l a n t type: morphology of l e a v e s , stem, r o o t zones etc.

A

- a g r i c u l t u r a l and i r r i g a t i o n p r a c t i c e s (see Eq. 2.110 - M, H, Q) - weather conditions ( s o l a r r a d i a t i o n , temperature, wind e t c . ) .

W

s o i l type, i t s t e x t u r e and s t r u c t u r e , i t s w a t e r h o l d i n g capacity

175 The a c t u a l water requirements of p l a n t s depend on weather: on the v a r i a b l e energy input o r output from the atmosphere. water and s o i l , i . e . mainly on the i n t e n s i t y of t h e s u n l i g h t , but a l s o on t h e i r r i g a t i o n water temperature, a i r hinriidity and wind v e l o c i t y . Their c h a r a c t e r i s t i c course shows a maximum during the sumner months i n a l l t h e c l i m a t i c zones of t h e northern hemisphere. A s t r a n s p i r a t i o n a f t e r sowing i s almost n i l , water requirements cover evaporation from the s o i l s u r f a c e i n o r d e r t o maintain s u f f i c i e n t s o i l moisture. I n the next period t r a n s p i r a t i o n i n c r e a s e s , reacliinp a maximum s h o r t l y before t h e period of maximum growth (Fig. 2 . 2 3 ) . mm monthly 125

evaporation

100

50

I

' I

' 2

'

I

3 ' 4 ' 5 ' 6

I

I

9 ' 1 0 '11 ' 1 2

7 ' 8

months

Fig. 2.23. Representation of t h e evapotranspiration of an annual p l a n t . The a c t u a l evapotranspirationET, approaches t h e value of t h e p o t e n t i a l evapotransp i r a t i o n ETp i n t h e period of maturing: FC - f i e l d capacity, WP - w i l t i n g point. Water is t h e r e g u l a t i n g f a c t o r of e n e r g e t i c processes during t h e t r a n s f o m t i o n of the organic matter i n a g r i c u l t u r a l systems. These e n e r g e t i c processes a r e c o n t r o l l e d by thermodynamic laws.

The expected y i e l d of the dry mtter can

be derived from t h e c h a r a c t e r i s t i c s of the change of t h e i n t e r n a l energy y

y

*n

hn

(7 - -Fi-

=

)

.

(2.113)

ymx

T - temperature t o t a l i n t h e r e l e v a n t period n T - temperature t o t a l during t h e y e a r of t h e maximum y i e l d

(OC)

(O)

hn

-

p r e c i p i t a t i o n i n t h e r e l e v a n t period

(m>

h

-

p r e c i p i t a t i o n t o t a l during t h e y e a r of t h e maximum y i e l d

(m)

-

( t ha-'

YmX

long-term maximum y i e l d of the dry

.

/ year)

matter The course of t h e change of t h e i n t e r n a l energy i s c h a r a c t e r i s t i c f o r t h e periods of growth and t h e p l a n t s i n question. Thermodynamic curves l i m i t t h e

176 c r i t i c a l periods i n which the lack of w a t e r considerably d e c r e a s s the y i e l d s . D i f f e r e n t p l a n t s require d i f f e r e n t amounts of s o i l moisture i n d i f f e r e n t periods of growth and seasons of t h e y e a r . They show a p r e f e r e n c e f o r a p a r t i c u l a r s o i l t e x t u r e , s t r u c t u r e and o t h e r p h y s i c a l c o n d i t i o n s . Some p l a n t s t h r i v e on well-drained s o i l , coarse-textured and w i t h a poor water-holding c a p a c i t y . Others show b e t t e r development i n more f i n e l y textured s o i l , with a h i g h e r d e r ree of moisture. The r o o t system of p l a n t s p e c i e s i s adapted t o a c c e p t

-

t h e r a i n from t h e s u r f a c e (shallow, dense, v a s t r o o t system)

-

the s o i l water

-

t h e groundwater (deep-rooted s p e c i e s ,

phreatophytes)

The arrangement and t h e d e n s i t y o f t h e r o o t system v a r i e s from s p e c i e s t o s p e c i e s . A r e l a t i o n s h i p between root systems and t h e water regime can be traced: s p e c i e s which prosper i n r a i n f a l l

may have a comparatively poor and shallow

system, while s p e c i e s i n a n a r e a where t h e r a i n f a l l does n o t p e n e t r a t e t o a g r e a t e r depth have a v a s t s u r f a c e system, Other s p e c i e s develop two t o t h r e e r o o t systems, which are s u p p l i e d fron! r a i n f a l l , groundwater and t h e s o i l moist u r e . The r o o t depth of one s i n g l e s p e c i e s dependson t h e s t r u c t u r e and depth of t h e s o i l p r o f i l e and i s influenced by t h e moisture conditions and groundwater t a b l e , which a r e interconnected with t h e c l i m a t e . I n deep well-drained s o i l s i n himid c o u n t r i e s p l a n t s a r e a b l e to accept water from a depth ranging from 0.3 t o 1 . 8 m , depending on t h e p a r t i c u l a r species and l o c a l c o n d i t i o n s . 'Re r o o t depth of semi-arid t o a r i d a r e a s exceeds t h e r o o t depth i n humid a r e a s by up t o two times. Seeds and s e e d l i n g s a r e a b l e t o accept water from t h e i r proximity o n l y . With t h e development o f t h e p l a n t , the r o o t s p e n e t r a t e i n t o deeper l a y e r s and spread h o r i z o n t a l l y .

A decrease i n the groundwater t a b l e has a n important e f f e c t on t h e y i e l d i n the case o f l i g h t and medium s o i l s . IJnder conditions o f heavy s o i l s , t h i s influence i s n o t s o s u b s t a n t i a l (Fig. 2 . 2 4 ) . R u t heavy soils do n o t allow a s u f f i c i e n t water supply i n dry seasons - y i e l d s a r e then considerably a f f e c t e d by weather c o n d i t i o n s . Light s o i l s , r e q u i r i n g high water t a b l e s , because of t h e i r low c a p i l l a r y r i s e , do n o t allow t h e necessary development o f t h e r o o t system. A decrease i n t h e water t a b l e under conditions o f a shallow r o o t system r e s t r i c t s y i e l d s because of the l a c k of water, w h i l e an i n c r e a s e has t h e same impact because o f the l a c k of a i r . Yields cannot be expected when t h e upper s o i l l a y e r , whose depth is 0 . 1 m i n t h e case of l i g h t and 0.4 m i n t h e case of heavy s o i l s , i s completely wetted because of t h e lack o f a i r i n t h e r o o t zone. I t is r a r e f o r a n uninterrupted supply of s o i l moisture from groundwater t o occur. Rut when t h e c a p i l l a r y r i s e and t h e s u c t i o n p r e s s u r e ensure an adequate supply of groundwater even i n dry p e r i o d s , n o t l i m i t i n g a s u f f i c i e n t supply o f a i r , t h e groundwater t a b l e is i n

177 the optimum p o s i t i o n f o r t h e s p e c i e s o f p l a n t i n q u e s t i o n t o achieve t h e rraximum y i e l d s . To achieve h i g h e r y i e l d s under t h e s e c o n d i t i o n s , t h e f l u c t u a t i o n of t h e groundwater t a b l e must b e r e s t r i c t e d ( F i g . 2 . 2 4 ) .

yield I00 O/O e

d 60°/0

2 0O/O 0.40

0.80

1.20

1.40

1.80

2.20 m

Fig. 2.24. I n t e r r e l a t i o n g h i p of y i e l d , s o i l q u a l i t y and depth of groundwater t a b l e according to Renetin (1963): a - sand, b - sandy loam, c - loamy c l a y , d - clayey loam, e - c l a y . A f a l l i n t h e groundwater t a b l e has a g r e a t e r e f f e c t on y i e l d from s o i l s w i t h lower c a p i l l a r i t y . A t t h e same l o c a t i o n , c h a r a c t e r i z e d by t h e s o i l q u a l i t y , t h e weather condit i o n s , t h e s i t i t a b i l i t y of p l a n t s and t h e q u a l i t y of seeds t h e r e l a t i o n s h i p between t h e water supply and t h e y i e l d can be expressed under s i m p l i f i e d condit i o n s , n o t t a k i n g i n t o account a g r i c u l t u r a l p r a c t i c e s i n c l u d h g t h e s u i t a b i l i t y , q u a l i t y and q u a n t i t y o f f e r t i l i z e r s , a s follows: Y

=

f

rn)

Y

- yield

D

- water d e l i v e r y ( n a t u r a l and a r t i f i c i a l ) and i t s timing

( t .ha-’ )

(2.114)

3 -1 (m .ha )

The course of t h i s f u n c t i o n !Fig. 2 . 2 5 ) proves t h a t maximum y i e l d s can only be achieved with an optimum water supply. A decrease below o r an i n c r e a s e above t h i s o p t i m m v a l u e c u t s y i e l d s . m e r i n g t h e water supply below t h e mentioned optimum v a l u e can i n c r e a s e t h e c o s t - b e n e f i t r a t i o , i . e . t h e f i n a n c i a l o r t h e economic y i e l d . Taking i n t o account economic reasons, i t i s necessary t o mention t h a t a long term oversupply of abundant water n o t only causes economic l o s s e s , but a l s o t h e gradual degradation of t h e s o i l l a y e r . IJnder t h e s e s i m p l i f i e d c o n d i t i o n s , f o r t h e purpose of water balances compilat i o n o n l y , t o t a l water requirements can be derived d i r e c t l y from the y i e l d R a = me ’ Y

(m3.ha-’)

m

- c o e f f i c i e n t of water requirements

(m3. t-’)(Tab.

Y

-

( t ha-1)

total yield

.

(2.115) 2.29)

178

yield

ha'

1.

water deliveries ( m3. h i ' 1 reduction in area

R~GIME

reduction unrestricted no in irrigation rdgirne more water rates needed

A

B

C

0

Fig. 2.25. I n t e r r e l a t i o n s h i p o f t h e y i e l d and t h e adequacy of the water d e l i very. The decrease i n water d e l i v e r y below minimum water requirements r e s u l t s i n no y i e l d . Regime: A - reduction of t h e area i r r i g a t e d , R - reduction i n i r r i g a t i o n r a t e s , C - u n r e s t r i c t e d regime, D - no mre water need+. Symbols: Y ,, - maximum y i e l d , Ymin - minimum y i e l d , ET - optimum evapo?P t - optimum water d e l i v e r y , - minimum (unavoidable) transpiration, D OP t water requirements. The c o e f f i c i e n t of water requirements depends on c l i m a t i c f a c t o r s . The equation was adapted f o r p r a c t i c a l a p p l i c a t i o n and c o e f f i c i e n t s derived e . g . Cherkasow (1950) (Tab. 2.30) Ra

k

t

=

-

0.1

. me . kt . Ye

3

y

c o e f f i c i e n t of t r a n s p i r a t i o n

(m3.ha-')

(2.116)

.

( 1 kg-')

ye - c o e f f i c i e n t of y i e l d Under the same c l i m a t i c conditions the transpiration/assimilation r a t i o of d i f f e r e n t s p e c i e s v a r i e s considerably. Some species a r e more e f f i c i e n t producers of dry matter than o t h e r s , with t h e same expenditure of water. This d i f f e r e n c e depends on t h e given morphological c h a r a c t e r i s t i c s , e.g. on the l e a f , stem and r o o t arrangement. As was shown above, t h e r a t e of t h e physiological processes, i.e. the trans-

piration/assimilation/production processes depends mainly on the supply of energy and moisture, and on the wind speed. Rut i t a l s o depends on the duration

179 TABLE 2.30

Prcduc ts

Coefficients k t (1.kg-’)

Yield Ye

mecd.kg-l)

Y(t.ha-])

Cereals : wheat

271-639

2.14

0.8-1.1

3 - 6

rye

431-634

2.25

0.8-1.1

3 - 6

barley oats

404-664 432-87 6

1.77 1.35

3 - 6 3 - 6

co rns

239-495

1.28

0.8-1 .1 0.8-1.1 0.7

5 - 8

Root crops: sugar b e e t

304-377

0.35

0.8-0.9

PO t a toes

285-575

0.25

0.8-1.0

50-90 40-80

Vegetables: Cucumbers

713

0.08

1.2-1.3

30-70

Tom toes

500- 650 250-600

0.10 0.15

1 .o-1.2

30-60 40-90

Cabbage

0 7-1.0

Table of transpi r a t i o n c o e f f i c i e n t s k t , y i e l d c o e f f i c i e n t s ye, water requirement c o e f f i c i e n t s me according t o Cherkasow (1950) and r e l e v a n t y i e l d depending i n a d d i t i o n on s o i l q u a l i t y , f e r t i l i z i n g and adequate s o l a r r a d i a t i o n . of t h e d a y l i g h t . The course of water requirements can, t h e r e f o r e , be derived from astronomic and meteorological f a c t o r s . The Hargraeves (1955) formula is based on an optimum s i m p l i f i c a t i o n of i n t e r n a l p l a n t and external environmental factors: R

opt

=

45.?

.

k

.

d

.T .

(0.38 - 0.0038 h )

(m)

k

- monthly consumptive-use c o e f f i c i e n t

d

- nonthly daytime c o e f f i c i e n t dependent upon l a t i t u d e

T - mean monthly temperature i n

(2.117)

OC

h - mean monthly r e l a t i v e humidity a t noon i n p e r cent (Tab. 2.31). To achieve optimum crop y i e l d s

( a > i n c l i m a t i c conditions, where t h e r e l e v a n t p l a n t s can be c u l t i v a t e d without a r t i f i c i a l watering, i r r i g a t i o n supplements t h e n a t u r a l water supply, ( b ) i n adverse c l i m a t i c conditions, where p l a n t s cannot be c u l t i v a t e d without an a r t i f i c i a l water supply, i r r i g a t i o n safeguards the undisturbed growth of p l a n t s . Under such conditions, i r r i g a t i o n r a t e s should be adequate t o achieve a t l e a s t minimum y i e l d s . I f t h e water q u a l i t y a v a i l a b l e i s n o t s u f f i c i e n t t o cover these minimum requirements, i t is vital t o reduce t h e e x t e n t of the a r e a irrigated.

180 TAULE 2.31

Consumptive use c o e f f i c i e n t s

3

Crop /Mon t h

4

5

6

7

0.11 0.25 0.29 0.33 0.31 0.41 0.70 0.64 0.67 0.74 0.12 0.38 0.32 1.34 1.42 1.40

Pasture Alfalfa Corn

Rice

8

9

10

0.32 0.67 0.42 I .44

0.32 0.64 0.26 0.51

0.22 0.40

11 Seasonal 0.14 0.41

0.10

0.55 0.72 0.73 0.62 0.28 0.45 0.30 0.31 0.28

Potatoes e a r l y Onions e a r l y Carrots

0.16 0.28

Peas

0.18 0.36

0.19

0.49

Reans Tom toes

0.52 0.31

0.66 0.32

0.64

0.28

0.15 0.28

0.66 0.71

0.51

0.33 0.36 0.40

0.67

0.58

0.81 0.19 0.27 0.36 0.15 0.10 0.03 0.25 0.51 0.17 0.34 0.34 0.50 0.48 0.32 0.42 0.48 0.24 0.22 0.45 0.43 0.46 0.51 0.51 0.38 0.60 0.41 0.41 0.69 0.15 0.18

0.32 0.55 0.87

Sugar b e e t s Ida ter melons Prunes Peaches

0.25 0.41 0.26 1.07

0.36 0.27 0.37 0.44

Monthly daytime c o e f f i c i e n t s Nlatitude

'5 25' 50'

1

2

1.01 0.91 0.91 0.86 0.72 0.76

3

4

1.02

5

0.99 1.03 1.01 1.03 1.12 0.99 1.11 1.28

6

7

1.03 1.11 1.13 1.32 1.32 1.00

1.0

11

12

1.03 0.98 1.02 1.09 1.00 0.97 1.20 1.01 0.89

0.98 0.89 0.73

1.00

8

9

0.89 0.68

Consumptive use c o e f f i c i e n t s a t Davis, C a l i f o r n i a and monthly daytime coeffic i e n t s i n the Hargreaves (1955) equation f o r the determination of t h e p o t e n t i a l evapotranspiration.

The a c t u a l water requirements depend on the f i e l d conditions, which change with the weather conditions. A p l a n t requires d i f f e r e n t q u a n t i t i e s of s o i l moist u r e , depending on t h e species and the s o i l , during i t s d i f f e r e n t stages of growth. Maximum t r a n s p i r a t i o n r a t e s appear i n a developing crop before assimilat i o n has reached i t s peak. The a c t u a l problems of how t o supplement these requiranents by i r r i g a t i o n and of how t o overcome adverse c l i m a t i c , s o i l and water conditions should be worked o u t on t h e t a s k of d a i l y measurements i n the course of t h e i r r i g a t i o n season.

181

Basic decisions include

-

amount of water required t o moisten the desired depth of s o i l (not smaller

and n o t g r e a t e r ) - a p p r o p r i a t e method and timing of i r r i g a t i o n ( a l s o t o reduce evaporation and percolation losses) - the coordination of o t h e r a g r i c u l t u r a l treatment processes w i t h the i r r i g a t i o n method and t h e timing of r a t i o n s .

2.6.2 Efficiency of I r r i g a t i o n Water IJse The e f f i c i e n c y of i r r i g a t i o n water u t i l i z a t i o n i s presently t h e key problem of water vanagemen t , because ( a ) i r r i g a t i o n water forms the main element i n water requirements on a global s c a l e . The e x t e n t of both t h e i r r i g a t e d land and the i r r i g a t i o n i n t e n s i t y

is increasing because of t h e increasing demand f o r food, caused p a r t l y by the world population boom and p a r t l y by improving l i v i n g standards; (b) i r r i g a t i o n i s an inherently consumptive use which considerably reduces the p o s s i b i l i t y of f u r t h e r re-use o r recycling; i r r i g a t i o n networks and t h e i r supply systems have a s u b s t a n t i a l and

(c)

l a s t i n g impact on t h e n a t u r a l environment. The economy of i r r i g a t i o n i s characterized by the r a t i o of t h e water withdrawal and t h e market u n i t , i . e .

wi l 1 = Y-Yo Y

- y i e l d under conditions of i r r i g a t i o n

Y

-

'

( t . ha-')

y i e l d under t h e same conditions, but without i r r i g a t i o n

Idi - water withdrawal f o r i r r i g a t i o n purposes

(m 3 .ha-'

per y e a r )

From t h e p o i n t of view of t h e p o p u l a t i o n ' s nourishment t h i s economy can be expressed by the r a t i o of t h e water withdrawal and the n u t r i t i v e value of the product

i'

=

I

I . (Y - Yo>

- n u t r i t i v e value of 1 t of t h e produced plant

(m 3 .J-1 )

(2.119)

(J.t-')

The b e n e f i t s of a l l investments i n i r r i g a t i o n p r o j e c t s depend on proper

water use i n t h e f i e l d i n conjunction with o t h e r a g r i c u l t u r a l inputs and cultur a l practices.

182

The planning and d e s i m of water development p r o j e c t s i n a g r i c u l t u r e should t h e r e f o r e be based on a water-use concept and should r e f l e c t t h e planned developnent of a g r i c u l t u r e r e s u l t i n g from t h e need f o r a f u r t h e r i n t e n s i f i c a t i o n and d i v e r s i f i c a t i o n of production, and t h e r e s u l t i n g changes i n a g r i c u l t u r a l practices.

Hulrar. s o c i e t y can determine only two o u t of t h e f o u r i n p u t v a r i a b l e s of t h e equation 3.112 namely: C - p l a n t s (seeds’ and

A - a g r i c u l t u r a l and i r r i g a t i o n

p r a c t i c e s . Hor.:ever, the nlutual r e l . a t i o n s h i p o f t h e s e v a r i a b l e s i s complex and can be solved r e l i a b l v enough on t h e b a s i s of system a n a l y s i s alone. This corn p l e x r e l a t i o n s h i p i s o f t e n n o t r e f l e c t e d by c u r r e n t p r a c t i c e . The s t r u c t u r e of a g r i c u l t u r a l systems and crop p a t t e m s is o f t e n s t i l l t h e r e s u l t of

-

t h e t r a d i t i o n a l food p a t t e r n ,

-

the given economic i n t e r e s t s ,

-

the t radi t i o n al ag r i cu l t u r al p r act i ce s, t h e l o c a l degree of r e l e v a n t know-how e t c . The equation of water balance and t h e optimum use of t h e s o i l moisture

a v a i l a b l e i n t h e absence of i r r i g a t i o n , o r t h e optimum use of n a t u r a l discharges a v a i l a b l e without s t o r a g e a r e seldom included among t h e r e l e v a n t d e c i s i o n c r i t e r i a i n a g r i c u l t u r e and i r r i g a t i o n development p r o j e c t s . The r e s u l t s of such a r o u t i n e approach a r e excessive i r r i g a t i o n requirements without s u f f i c i e n t c a m e and exaggerated claims on water withdrawal and s t o r a g e .

A change i n t h e r e l e v a n t engineering approach is needed, i n c l u d i n g a n o p t i mization of cropping p a t t e r n s and a harmonization of t h e r e s u l t i n g t o t a l water requirements w i t h t h e course of n a t u r a l w a t e r supply: s o i l moisture, p r e c i p i t a t i o n , d i s c h a r g e s and groundwater resources a v a i l a b l e d u r i n g t h e v e g e t a t i o n season. This harmonization o f i r r i g a t i o n requirements with a v a i l a b i l i t y of w a t e r without s t o r a g e may a l s o r e q u i r e changes i n t h e t r a d i t i o n a l food p a t t e r n : e . g . i n a r i d c o u n t r i e s w i t h heavy r a i n f a l l and high r i v e r discharges a t t h e beginning of t h e v e g e t a t i o n season, t h e i n t r o d u c t i o n of precocious p o t a t o e s i n s t e a d of r i c e c u l t i v a t i o n can h e l p t o ensure t h e food supply without extensive water s t o r a g e , which r e s u l t s i n high evaporation l o s s e s ( F i g . 2.26). Arrangements f o r i n c r e a s i n g t h e e f f i c i e n c y of water u t i l i z a t i o n d u r i n g a g r i c u l t u r a l production i n c l u d e - t h e c r e a t i o n of a n optimum s t r u c t u r e o f a g r i c u l t u r a l s y s t e m , i.e. the optimum r a t i o of t h e producers and consumers of carbonic matter,

-

t h e o p t i m i z a t i o n of t h e crop p a t t e r n , p r e f e r r i n g p l a n t s and seeds with lower

water requirements corresponding t o t h e p a t t e r n o f water occurrence, thus ensuring a n optimum u t i l i z a t i o n of t h e s o i l moisture, r a i n water and n a t u r a l s u r f a c e water d i s c h a r g e s , - t h e a p p r o p r i a t e p r e p a r a t i o n of t h e land, i n c l u d i n g e f f i c i e n t measures t o i n c r e a s e i n f i l t r a t i o n and transform overland flow i n t o subsurface r u n o f f ,

183 POPULATION NUMBER FINANCIAL RESOURCES

TRADITION

I

I

-*

FOOD

FOOD QUANTITY 8 STRUCTURE

IMPORT

,q 1 ,'

I

I

iTRIBUTION OF

RAINFALL

IRRIGATION

I I

CROP

)stNc

STORAGE

6 t h No

Fig. 2.26. Block diagram d e p i c t i n g t h e h i e r a r c h y of necessary b a s i c measures f o r safeguarding of food f o r population.

-

t h e c o n s t r u c t i o n of small r e s e r v o i r s , d i v e r s i o n dams etc. i n o r d e r to de-

c r e a s e t h e s l o p e of t h e t e r r a i n and slow down t h e s u r f a c e r u n o f f . - t h e u t i l i z a t i o n o f a p p r o p r i a t e water-saving i r r i g a t i o n methods, corresponding t o t h e s p e c i e s of t h e crops c u l t i v a t e d and t h e r e l e v a n t c u l t i v a t i o n practices, - t h e r e d u c t i o n of water l o s s e s d u r i n g conveyance by a d a p t i n g t h e design of conveyance s t r u c t u r e s t o l o c a l conditions e . g . l i n e d c a n a l s i n pervious s o i l s , closed c u l v e r t s i n a r i d c l i m a t e and by a p p r o p r i a t e maintenance and by economic a l operation, - t h e management o f a g r i c u l t u r a l s y s t e m on t h e b a s i s of d a i l y agrohydrometeorological d a t a , i . e . by watering only i n p e r i o d s of a s u b s t a n t i a l decrease i n s o i l m i s t u r e below t h e optimum v a l u e , without any o v e r i r r i g a t i o n ,

-

t h e drainage and re-use o f excess i r r i g a t i o n w a t e r ,

184

Investment a n d

Fig. 2 . 2 7 . Block diagram of water d e l i v e r y management i n a g r i c u l t u r e t o safeguard t h e environmental equilibrium of t h e a p i c u l t u r a l system.

-

the reduction of evaporation l o s s e s , e . g . by p r o t e c t i n g t h e s o i l s u r f a c e by

means of wind-breaks, i r r i g a t i o n a t n i g h t e t c . , - the re-use of municipal, i n d i i s t r i a l and a g r i c u l t u r a l waters f o r the purpose of i r r i g a t i o n ,

-

the observation of optimum a g r i c u l t u r a l p r a c t i c e s during f e r t i l i z e r and

pesticide application. There a r e e s s e n t i a l l y three ways of ensuring t h e adequate nourishment of t h e population : ( a ) s e l f - s u f f i c i e n c y across the e n t i r e range and assortment of necessary a g r i c u l t u r a l products, cb)

over-production and export of s e l e c t e d a g r i c u l t u r a l goods, thus forming

f i n a n c i a l resources t o supplement t h e lacking v a r i e t i e s by means of import, ( c ) exporting i n d u s t r i a l goods o r raw m a t e r i a l s with t h e same goal. The o v e r - i n t e n s i f i c a t i o n of a g r i c u l t u r e , namely t h e over-application of fert i l i z e r s and chemical substances i n p l a n t p e s t control a s well a s i n s u f f i c i e n t p r o t e c t i o n measures r e s u l t i n g i n s o i l wash,the wastes from farm rrachinery and r e p a i r shops and highly concentrated l i v e s t o c k production r e s u l t s i n s u r f a c e

185 and groundwater p o l l u t i o n and threatens t h e q u a l i t y of products and of t h e environment. The s c i e n t i f i c coordination

of the crop p a t t e r n with both t h e agropedologic a l and t h e hydrometeorological conditions r e s u l t s i n an increase i n y i e l d s without a s u b s t a n t i a l increase i n water requirements for i r r i g a t i o n , a s w e l l a s i n an increase i n the t o t a l n u t r i t i v e value p e r h e c t a r e c u l t i v a t e d . It helps t o maintain the equilibrium of the biogeochmical cycles i n t h e a g r i c u l t u r a l system, whose l a s t i n g function i s p o s s i b l e only under the conditions of the s t a b i l i t y of energy and matter input and o u t p u t , and under t h e conditions of an e q u i l i b r i i m of t h e system and i t s environment (Fig. 2 . 2 7 ) .

2.6.3

Water f o r I r r i g a t i o n and i t s Quality

The supplementation of s o i l moisture t o s a t i s f y crop water requirements is the main, but not t h e s i n g l e purpose of i r r i g a t i o n . By means of i r r i g a t i o n bioelements and o t h e r matter which improves p l a n t production o r s o i l conditions can e i t h e r be n a t u r a l l y o r a r t i f i c i a l l y supplied, favourable microclimatic cond i t i o n s t o support p l a n t growth maintained, and m t t e r including p e s t s which jeopardizes t h e s o i l s t r u c t u r e and t e x t u r e o r the h e a l t h of p l a n t s removed. From t h i s p o i n t of view, i r r i g a t i o n can be categorized a s follows (a)

proper i r r i g a t i o n (supplementary watering),

(b)

f e r t i l i z i n g and remedial ( p l a n t h e a l t h promoting) i r r i g a t i o n ,

(c)

protective irrigation,

(d)

s o i l leaching i r r i g a t i o n .

The q u a l i t y of t h e water used f o r i r r i g a t i o n depends on the required purpose, on t h e s o i l p r o p e r t i e s and on t h e i r r i g a t i o n operation. The b a s i c requirements a f f e c t i n g t h e qiiality of water used f o r i r r i g a t i o n can be surrmarized as follows:

(a) i t should favourably influence p l a n t growth and t h e q u a l i t y of the prodiicts grown,

(b) i t should not cause breakdowns during t h e i r r i g a t i o n operation, ( c ) it must n o t cause s a n i t a r y complaints, e i t h e r during i t s operation o r during the processing and consimption of the r e l e v a n t a g r i c u l t u r a l products, (d) water,

i t should not endanger t h e q u a l i t y of the s u r f a c e water and t h e ground-

l e ) i t must not d e t e r i o r a t e t h e s t r u c t u r e , p o r o s i t y and o t h e r agrochemical p r o p e r t i e s of the s o i l p r o f i l e . The q u a l i t y of t h e water used f o r i r r i g a t i o n has t o be categorized on the basis of i t s r e l e v a n t physical, chemical, biological and b a c t e r i o l o g i c a l prop e r t i e s (Tab. 2.32). An important property of water, deciding on i t s s u i t a b i l i t y f o r i r r i g a t i o n , i s t h e s a l i n i t y , frequently expressed a s t h e sodium percentage, t h e amount of sodium Na p r e s e n t i n r e s p e c t of t h e c a t i o n i c concentration. Rut generally mre important is t h e sodium- adsorption r a t i o SAR, which expresses

186 TABIE 2.32

ategories

Indicators A good Oxygen content (mg.1-I) a t IOOC a t 20’~

> 11

Dissolved matter (mg.1-I) Chlorides (mg .1-l)

<800

saturation

800-1200 300- 400 250- 300 t r a c e s C1

Toxic r a t t e r

C marginally admiss ib 1e

50%

> 9

<300 (250

(mg. I-’)

Sulpha t e s

B conditioned

> 1200 > 400 > 300 C 0 2 , C1

H2S, F

(Img.l-l) Radioactivity

Razz’ S r88

Odour Temperature

i n spring

OC

in s m e r

OC

Sediment s i z e

C1

c2 c3 c4

Salinity

Low Medium High Extreme

mediocre

1C-15 15-20

15-35

I a , I b , I1

Electrical conductivity fmnhos.cm-J >

0 0.25 0.75 2.25

slight

- 0.25 - 0.75 - 2.25 - 6.0

s1

offensive

>35

0.005-0.1 0.001-0.0051’

Inn’)

Water p o l l u t i o n c l a s s Degree

3. 3.

(Curie)

0.12 ) IV

111

Alkali hazard

s2

s3

s4

bw

Medium

High

Extreme

(9

9 - 17

<7 <5

<3

17-24 7 - 1L 14-20 5 - 11 11-16 3 - 8 8-12

>24 >20

b16 )12

Categories of water q u a l i t y f o r i r r i g a t i o n purposes and of i t s s u i t a b i l i t y according t o t h e a l k a l i and s a l i n i t y hazard (derived from t h e graphical repres e n t a t i o n of t h e US S a l i n i t y Laboratory i n R i v e r s i d e ) . 1) f i n e sediments have a p o s i t i v e impact on t h e f e r t i l i t y of highly pervious s o i l s , b u t decrease t h e q u a l i t y of heavy s o i l s , r e s t r i c t i n g t h e perviousness and a e r a t i o n 2) cause sedimentation i n t h e canal and p i p e l i n e network. the r e l a t i v e a c t i v i t y of sodium ions i n exchange r e a c t i o n s with s o i l , i n which calcium Ca and mgnesium Mg i n t h e s o i l a r e replaced by t h e sodium i n t h e water.

The SAR is c a l c u l a t e d f r a n t h e i o n i c concentrations i n millimoles of r e l e v a n t bioeleinents according t o t h e following formula:

= I T Na’

sAR

(2.120)

187

The second basic property of i r r i g a t i o n water is the a l k a l i hazard, measured as e l e c t r i c a l conductivity, which r e f e r s t o the conductance of one centimeter cube of water on a s i d e measured a t 25

OC.

Depending on these two c r i t e r i a ,

which possess dividing points f o r low, medium, high and very high values, i r r i gation water can be characterized by sixteen combinations of s a l i n i t y , i . e . sodium adsorption r a t i o and a l k a l i hazard (Tab. 2.32). Water with a low a l k a l i hazard and low s a l i n i t y can be used f o r i r r i g a t i n g almost a l l crops with any type of s o i l . Water with high s a l i n i t y o r a high a l k a l i hazard is not s u i t a b l e f o r i r r i g a t i o n under n o m l conditions. TABLE 2.33

Species high

S a l t tolerance medium

lOW

Fruit trees

dates

grapes, c i t r u s f r u i t pears, apric o t s , peaches, plums, apples

Field crops, vegetables

sugarbeet, beetr o o t , savoy, rape

barley, rye, o a t s , r i c e , f l a x , tomatoes, asparagus, melons, lettuce, carrots, spinach, capsicum, gar 1i c , gourds , , sunflowers, wheat, corn clover

Fodder crops

peas, celery, cabbage, potatoes

alfalfa

S a l t tolerance of crops, i . e . t h e i r a b i l i t y t o survive under conditions of increasing s a l i n i t y . When i r r i g a t i o n with water which has medium o r high s a l i n i t y , salt-tol-erant crops should be cultivated (Tab. 2.33). Measures to counteract against the s a l i n a t i o n of the s o i l p r o f i l e include especially good drainage and leaching. Idhen i r r i g a t i n g with water whose u t i l i z a t i o n f o r t h i s purpose i s conditional, due t o the sanitary hazard (Tab. 2.36) special measures a r e required.

In addition, protecting zones without i r r i g a t i o n by such water should be established around dwelling areas and communication l i n e s f o r pedestrians.

2.6.4 I r r i g a t i o n a s Supplementary Watering S o i l moisture can be controlled by means of an i r r i g a t i o n and/or drainage system. An i r r i g a t i o n system consists of five subsystems: storage, transmission, d i s t r i b u t i o n , s o i l moisture and, exceptionally, a l s o underground aquifers. I r r i g a t i o n basically safeguards the supplementation of the water which escapes from the vegetative system, especially by evapotranspiration, thus cont r i b u t i n g t o i t s undisturbed development. I t s f e a s i b i l i t y depends on s o i l and

188 land conditions !Tab. 2 . 3 4 ) . The t o t a l water supply required f o r one i r r i g a t i o n season is t h e sum of uses and l o s s e s , derived from seasonal consumptive use and leaching requirements, less t h e amount of r a i n f a l l and groundwater input i n t h e vegetation period which c o n t r i b u t e s t o t h e moisture of t h e s o i l l a y e r i n quest i o n and less t h e u t i l i z a b l e moisture-holding capacity of s o i l a t the beginning of t h i s period. TABLE 2.34 S imp1i f i e d charac teris t i c s

Class

~~

~~~

Good i r r i g a b l e land

No erosion o r gravel problem, adequate permeability, good s o i l s t r u c t u r e and t e x t u r e

11

Moderately

S l i g h t e r o s i o n , gravel problem, low permeability, s l i g h t l y undiilated, s l i g h t s a l i n i t y etc.

111

khrginally irrigable

Moderate g r a v e l , s l o p e , e r o s i o n , deep s o i l , wetness problem e t c .

IV

Irrigable s p e c i a l conditions

Steep s l o p e , shallow s o i l , g r a v e l , undulated surface etc.

V

Undetermined s u i t ability for irrigation Non-i r r i g a b l e land

Salinity, etc.

I

VI

Rocky land, marsh, flooding problan e t c .

S i m p l i f i e d FA0 c l a s s i f i c a t i o n of land according t o i t s s u i t a b i l i t y f o r i r r i g a tion.

Ra

-

t o t a l annual i r r i g a t i o n demand seasonal consumptive use of the pland i i n t h e vegetation period

Eei-

leaching requirements, approximately 0 t o !see paragraph 2.6.7)

Rli-

(m3 .ha-’ per y e a r ) 3 (rn .ha-’

per y e a r )

50% of Eei P

V

-

d e c i s i v e t o t a l r a i n f a l l i n t h e vegetation period ( f o r planning and design purposes t h e r a i n f a l l of t h e vegetation period i n a medium dry year should be used)

(rn 3 .ha-’ p e r y e a r )

di - c o e f f i c i e n t of t h e r a i n f a l l e f f i c i e n c y (depends on t h e s o i l q u a l i t y : 0.5 f o r heavy s o i l s , 0 . 6 f o r sandy s o i l s , 0.7 f o r clay s o i l s , 0.75 f o r loamy soils)

Wwi- u t i l i z a b l e moisture-holding capacity of s o i l a t t h e beginning of t h e vegetation p e r i o d , formed i n t h e winter period

(m3 .ha-’)

189 W

.-

t h e groundwater i n p u t i n the v e g e t a t i v e season, depending on the c a p i l l a r i t y of s o i l s and t h e groundwater depth

(m3.ha-l)

ef - c o e f f i c i e n t of f i e l d e f f i c i e n c y , depending mainly on the irrigatio.1 method (Tab. 2.35) Ai - a r e a of crop i

(ha)

I t goes without sayinz t h a t the value of the t o t a l withdrawal is n

(2.122) A

- area

Ac.-

(ha)

delivery l o s s e s (see paragraph 2.6.8)

(m3

1

ed - c o e f f i c i e n t of water d e l i v e r y TABLE 2.35

Methods of irrigating

Definition

Coefficient of f i e l d efficiency ef

Bas i n (level-border) irrigation

Floodin,q of l e v e l p l o t s surrounded by small dikes. Water l a y e r 0.150.3 m is held u n t i l complete infiltration.

0.4 - 0 . 6

Border irrigation

Water d e l i v e r y a t the high end of long s t r i p s , e . g . from d i t c h e s running along contours, drainage a t t h e i r low end, depth of the overland flow 0.03-0.07 m.

0.6 - 0.7

FurTow irrigation

Controlled flooding frcm furrows o r corrugations running between crop rows.

0.7 - 0.8

Subsurface irrigation

Creation of a r t i f i c i a l groundwater t a b l e , e . g . by d e l i v e r y of water by means of underground pipes.

Sprinkler irrigation

A r t i f i c i a l r a i n f a l l from overhead s p r i n k l e r s supplied e.g. from pipes. Mozzles discharge t h e water from pipes i n d r i p s along t h e length of the Dlant row.

Drip ( t r i c k l e ) irrigation

0.6

-

(a) 0.8

0.7 - 0.87

0.85-0.92

Categorization of i r r i g a t i o n and i r r i g a t i o n f i e l d e f f i c i e n c i e s : ( a ) c o e f f i c i e n t depends on t h e hydraulic conductivity of s o i l s and on t h e s u r f a c e runoff caused. The t o t a l r a i n f a l l with an 80% frequency of occurrence i n t h e vegetation period may be considered a s d e c i s i v e , depending on l o c a l climatic conditions and

190

y i e l d . The e f f i c i e n c y of t h e r a i n f a l l u t i l i z a t i o n depends on evapotranspiration and outflow, i . e . on c l i m t o l o g i c a l , geomorphological, s o i l and vegetation factors. The crop i r r i g a t i o n depth which has t o be penetrated by watering, and thus the crop water requirements too, depends on the depth of t h e r o o t system (Paragraph 2.6.1). The u t i l i z a b l e moisture-holding

capacity Tdwi of s o i l a t t h e beginning of t h e

vegetation period a l s o depends on t h e r o o t depth and on t h e c a p i l l a r y rise of the s o i l s t r u c t u r e . Its value can be derived according t o formula Wwi = 25

. nc . hi

(m3. ha-’)

n

-

average value of the c a p i l l a r y p o r o s i t y

(%)

hi

-

e f f e c t i v e depth o f t h e r o o t system

(m)

C

Hal?

(1976) from the

(2.123)

This value f l u c t u a t e s between 150 m3 .ha-’ i n l i g h t sandy s o i l s and 350 m3.ha-l i n clay s o i l s f o r c e r e a l s , root-crops and fodder crops with t h e except i o n of corn and b e e t r o o t , whose moisture holding capacity is some 30% higher. Higher values can be a l s o expected f o r a l f a l f a and i n orchards, when they f l u c t u a t e between 200 and 250 m3 .ha-’. The groundwater input i n t h e v e g e t a t i v e season Id depends mainly on t h e gi groundwater t a b l e depth and on t h e s o i l s t r u c t u r e . According t o Kostjakov (1951), t h e value of t h e groundwater input t o the seasonal consumptive use of p l a n t s does not exceed an average of 5% when t h e groundwater t a b l e depth exceeds 2 . 5 m, reaching 25% f o r deep r o o t systems and smaller groundwater t a b l e depths. Under normal conditions, t h e c a p i l l a r y r i s e does not exceed 3 m , i . e . the groundwater cannot supplement t h e water requirements of c u r r e n t p l a n t s when deeper than 3 m below the land surface. The economy of p l a n t production and t h e e f f i c i e n c y of i r r i g a t i o n water a p p l i c a t i o n a r e c l o s e l y interconnected. The a c t u a l i r r i g a t i o n r a t e s a r e to be determined and i r r i g a t i o n operation managed on t h e b a s i s of t h e measured a c t u a l evapotranspiration. The water r a t e s must n o t overload e i t h e r t h e p l a n t o r t h e s o i l , which r e s u l t s i n a degradation of both, and they should not harmfully a f f e c t t h e underground biosphere.

IJseless l o s s e s through unused outflow, deep p e r c o l a t i o n and excessive unproductive evaporation should a l s o be avoided. I r r i g a t i o n r a t e s can f u r t h e r be derived from t h e a c t u a l soil moisture, c a p i l l a r y rise and t h e necessary depth of water. The c a p i l l a r y porosity p r a c t i c a l l y corresponds t o t h e f u l l f i e l d capacity FC. The i r r i g a t i o n r a t e a l s o depends on t h e method of i r r i g a t i o n

191 and on t h e conditions of operation, which have a b a s i c impact on l o s s e s , i . e . on t h e c o e f f i c i e n t of i r r i g a t i o n e f f i c i e n c y = -loo . (FC

R

- ida) . hr

ef

r

-

irrigation rate

FC

-

f i e l d capacity

Wa

-

a c t u a l s o i l moisture

R

(m3. ha-' )

(2.124)

hr - e f f e c t i v e depth of t h e r o o t system ef

-

c o e f f i c i e n t of i r r i g a t i o n e f f i c i e n c y

2.6.5

F e r t i l i z i n g and Remedial I r r i g a t i o n

F e r t i l i z i n g i r r i g a t i o n serves t o supplement important nutriments. For t h e purpose of f e r t i l i z i n g i r r i g a t i o n t h e following s o l u t i o n s a r e used: (a) (b)

s o l u t i o n s of f e r t i l i z e r s , flood w a t e r s ,

(c) (d)

municipal, i n d u s t r i a l and a g r i c u l t u r a l waste waters and sludges, dung and d u n p a t e r .

The annual i r r i g a t i o n requirements and the i r r i g a t i o n retes depend and a r e t o be determined on t h e b a s i s of t h e p r e v a i l i n g purpose of t h e i r r i g a t i o n which can be e i t h e r supplementary watering o r f e r t i l i z a t i o n o r waste water disposal. When i r r i g a t i o n i s expected t o be t h e p r e v a i l i n g purpose of t h e i r r i g a t i o n by waste waters, t h e water requirements a r e expressed by t h e following function R f = f (S ; C ; A ; W , N , M , t )

(m3 .ha-'

p e r year) (2.125)

For an explanation of f a c t o r s S , C , A, W see equation 2.112

M

-

t

-

N

nutriment requirements (t.ha-') s u i t a b i l i t y of waste waters, i . e . q u a l i t y and e x p l o i t a b i l i t y of nutriment contents period from t h e beginning of the vegetation period.

When waste water disposal is expected t o be t h e p r e v a i l i n g purpose of irrig a t i o n , the seasonal i r r i q a t i o n requirements R

f a r e t o be determined with a

view t o t h e annual production of waste waters (m 3 p e r year)

Ra - annual i r r i g a t i o n requirements

(m3 per y e a r )

(2.126)

192

efo- off-season c o e f f i c i e n t of farm l o s s e s R

ao

-

average u s e f u l i r r i g a t i o n r a t e off-season

(m3 p e r y e a r )

When f e r t i l i z a t i o n i s expected t o be t h e p r e v a i l i n g purpose of i r r i g a t i o n , the annual i r r i g a t i o n demand i s t o be derived on t h e b a s i s of t h e requirements of t h e nain nutriment R = - Nm f no . Co N

n

average requirements of t h e r e l e v a n t nutriment, nitrogen N , phosphons F o r potassium K , derived from t h e cropping p a t t e r n

-

average c o e f f i c i e n t of t h e e x p l o i t a b i l i t y of the nutriments frcm waste waters

-

average concentration of t h e nutriment i n waste waters

O

C

( t . h a -1 )

-

O

.

( t m-3)

Before being used f o r i r r i g a t i o n , sewage e f f l u e n t should be (a) (b)

t r e a t e d mechanically o r a t l e a s t s t r a i n e d by f i n e racks, o r t r e a t e d b i o l o g i c a l l y , i f necessary, and accumulated i n t h e medium term o r i n t h e s h o r t t e r n f o r balancing the

(c) i n f l m of t h e waste water and the required i r r i g a t i o n r a t e s . - Na Po - Pa f = Na O 4N

f

-

KO - K

T + aT

(2.128)

i n d i c a t o r of t h e f e r t i l i z i n g e f f i c i e n c y

No, Po, K

-

content of t h e m i n nutriments: nitrogen N , phosphoruj and potassium K i n 1000 m of t h e sewage e f f l u e n t

(kg)

Na, Pa, Ka - average demand of n i t r o g e n N , phosphorus P and potassium K f o r 1

h e c t a r e of c u l t i v a t e d land, derived f r a n t h e cropping p a t t e r n and the required y i e l d .

The p o s i t i v e impact of these b a s i c nutriments can be increased by t h e presence of o t h e r compounds and elements, namely t r a c e elements, by the presence of organic matter, matter forming humus o r rnatter supporting t h e growth of p l a n t s . But they can a l s o , through t h e presence of t o x i c matter, considerably

l i m i t such a n impact. The s a n i t a r y e f f i c i e n c y of t h e s e fonns of i r r i g a t i o n , c h a r a c t e r i z i n g t h e e f f e c t of t h e f i l t r a t i o n through t h e s o i l l a y e r on t h e q u a l i t y of t h e r e t u r n flow, can be expressed by t h e i n d i c a t o r of t h e s a n i t a r y hazard

193 TABLE 2.36

Crops :

Indispensable measures

For d i r e c t consumption: a . eaten raw:

a . mechanical, b i o l o g i c a l and t e r t i a r y water t rea tmerit b. b a c t e r i o l o g i c a l checking of water q u a l i t y 6100 b a c t e r i a c o l i per ml) c. p r o t e c t i n g period of 2 1 days without i r r i g a t i o n before h a r v e s t d . s p r i n k l e r i r r i g a t i o n prohibited

b. not eaten raw

a . and b. as above

c. p r o t e c t i n g period of 14 days without i r r i g a t i o n before harvest Fodder crops: a . grazing

a . mechanical, b i o l o g i c a l and t e r t i a r y water treatment b . b a c t e r i o l o g i c a l checking of water q u a l i t y (d000 b a c t e r i a c o l i per m l ) c. grazing allowed a f t e r drainage and evapor a t i o n of i r r i g a t i o n water d . grazing of milk cows prohibited

b. consumed dry

a . a s above b. no grazing allowed (fences)

Parks and s p o r t s f i e l d s :

a . mechanical, b i o l o g i c a l and t e r t i a r y water treatment b. b a c t e r i o l o g i c a l checking of water q u a l i t y (
Lumber, i n d u s t r i a l crops i n c l . f l a x and hemp:

Mechanical and b i o l o g i c a l treatment

Indispensable measures f o r i r r i g a t i o n with waste waters.

(2.129)

Q, - volume of t h e s u r f a c e outflow from i r r i g a t i o n Q,

-

volume of groundwater outflow from i r r i g a t i o n

(m3)

(m3>

194 Rf

-

volume of water applied

qs

-

q u a l i t y i n d i c a t o r of s u r f a c e outflow

(eg. BOD5>

-

q u a l i t y i n d i c a t o r of groundwater o u t f l m

-

q u a l i t y i n d i c a t o r of i r r i g a t i o n water applied

qg qf

\ h e n applying t h e s o l u t i o n s of mineral f e r t i l i z e r s , concentrations of 0.1 t o

0.5 % and s p r i n k l e r o r d r i p i r r i g a t i o n methods should be used. S p r i n k l e r irrig a t i o n can a l s o be applied t o spread s o l u t i o n s of p e s t i c i d e s , s t i m u l a t o r s and agrochemicals which p r o t e c t a g a i n s t p e s t and p l a n t d i s e a s e s , i . e . a s i r r i g a t i o n which i r p r o v e s p l a n t h e a l t h . I f t h e l a y e r s of s o i l above the groundwater l e v e l a r e uninjured and s t r o n g enough, i t is p o s s i b l e t o eliminate a l l dangerous f o m s of b a c t e r i a before p e n e t r a t i o n i n t o s u r f a c e and groundwater resources, but not t o eliminate sane chemical substances which might represent a c u t e o r p o t e n t i a l h e a l t h hazards. Water which is hazardous from a s a n i t a r y p o i n t of view cannot be used on land whose s o i l depth i s not deep enough t o guarantee t h e necessary b i o l o g i c a l f i l t r a t i o n needed t o safeguard t h e groundwater from contamination. I r r i g a t i o n with such waters must be prohibited f o r t h i s reason e . g . i n t h e flood p l a i n of water courses whose water is used f o r the supply of t h e population. The a p p l i c a t i o n of not only toxic o r i n f e c t i o u s matter, b u t a l s o high con-

c e n t r a t i o n s o r overdoses of generally harmless chemicals, might represent a c u t e o r p o t e n t i a l h e a l t h and environmental hazards, jeopardizing (a)

t h e h e a l t h of t h e s e r v i c e personnel,

(b) (c)

the s o i l q u a l i t y ,

t h e a i r and water q u a l i t y ,

(d) t h e q u a l i t y of a g r i c u l t u r a l products. They a l s o have a negative impact on t h e i r r i g a t i o n operation and a c t aggress i v e l y on s t r u c t u r e s and technological equipment. When lcoking f o r t h e o r i g i n of c u r r e n t rrass d i s e a s e s , i t is necessary t o take the f a c t o r s of t h e environment i n t o account, a s w e l l a s t h e l o n r t e r m consumption of products t r e a t e d by t h i s f e a s i b l e , b u t unnatural method, which has not y e t been s u f f i c i e n t l y invest i g a t e d , e s p e c i a l l y from t h e p o i n t of view of i t s l o n r t e r m impact.

2.6.6

Protective Irrigation P r o t e c t i v e i r r i g a t i o n is used t o safeguard t h e optimum conditions f o r the

undisturbed development of p l a n t s . It includes c l i m a t i z i n g and p u r i f y i n g irriga t i o n . The temperature and humidity i n p l a n t systems can be c o n t r o l l e d by climatizing i r r i g a t i o n i n order t o achieve favourable conditions f o r f u r t h e r development: Anti-frost i r r i g a t i o n p r o t e c t s t h e p l a n t system a g a i n s t t h e ;.,pact

of f r e e z i n g

195 temperatures. This type of i r r i g a t i o n i s a p p l i e d e x c l u s i v e l y by means of sprinkl e r s , d e l i v e r i n g h e a t energy t o t h e a i r , t h e s o i l and t h e p l a n t s . The i n p a c t of t h i s i r r i g a t i o n i s based on t h e p h y s i c a l p r o p e r t i e s of w a t e r , e s p e c i a l l y on i t s high h e a t c a p a c i t y , t h e h i g h v a l u e of t h e l a t e n t h e a t of s o l i d i f i c a t i o n and i t s low h e a t c o n d u c t i v i t y . The temperature of t h e water applied g e n e r a l l y Eluctriates between 5 aria 12OC. When i t drops t o O°C

, the

ice

my cover t h e l e a f s and blossoms, thus forming a n irisu!ating l a y e r and supplying them with its l a t e n t h e a t of s o l i d i f i c a t i o n . By s p r i n k l i n p , t h e humidity of t h e a i r i n c r e a s e s , thus decreasing t h e a i r albedo and slowing down t h e cooling of the p l a n t system. The e f f i c i e n c y of t h i s a n t i - f r o s t i r r i g a t i o n depends not only on t h e intens i t v of t h e water a p p l i c a t i o n and i t s temperature, but a l s o on t h e wind v e l o c i t v , t h e r e l a t i v e humidity of t h e a i r , and on t h e p l a n t s p e c i e s and its s t a g e of growth. A n t i - f r o s t i r r i g a t i o n has proved s u f f i c i e n t down t o

-

6OC. I r r i g a t i o n

r a t e s f o r t h i s purpose range between 1 and 3 m p e r h o u r , depending on t h e above c o n d i t i o n s . According t o Achtnich (1957), t h e w a t e r requirements f o r a n t i - f r o s t i r r i g a t i o n can be determined a s follows:

Raf =

.

.

11.15

.

h

K

.

(80 + Tw)

vw

(T - 2 )

(m per hour)

(2.130)

h - h e i g h t of t h e p l a n t P vw - wind v e l o c i t y ' I - temperature cf t h e s u r f a c e a i r l a y e r

(OC)

TW - water temperature

C°C)

K - c o e f f i c i e n t corresponding t o t h e a r e a of i r r i g a t e d leaves and stems 2.6.7

S o i l Leaching I r r i g a t i o n

The goal of leaching i r r i g a t i o n i s t h e p r o t e c t i o n of t h e s o i l q u a l i t y , i . e .

i t s chemical composition, t e x t u r e and s t r u c t u r e . The b a s i n method i s generally used f o r l e a c h i n g , aiming a t t h e renaval of excessive s a l t s from t h e s o i l SUT' face and r o o t zone, e s p e c i a l l y of c a r b o n a t e s , c h l o r i d e s , s u l p h a t e s and n i t r a t e s , which may g r a d u a l l y r e s u l t i n a decrease i n y i e l d s a s w e l l a s i n s o i l degradation. Leaching i n c r e a s e s t h e o r i g i n a l crop water requirements a t cW

R a l = Ra a

Ra

-

(m3.ha-'

w

i r r i g a t i o n requirements w i t h o u t leaching

p e r y e a r ) (2.131)

196 cw - concentration of s a l t s i n t h e i r r i g a t i o n water

(g.1-I)

ca - permissible l i m i t i n g concentration of s a l t s i n s o i l water

(g.1-I.)

The water requirements f o r a decrease i n t h e s a l i n i t y of s o i l s c o n s i s t of the volume needed f o r the s o l u t i o n and washing away of s a l t s R1, t h e volume needed t o supplement t h e s o i l moisture R2 a t t h e value of t h e f i e l d capacity FC, and t h e l o s s e s Ral = R 1

R1

-

+ R2 + A1 + A2 - P

- Ws

volume needed f o r t h e s o l u t i o n and washing away of s a l t s

R2 - volume needed f o r t h e supplementation of

(m3 .ha-‘)

(2.132)

(m’.ha-l) (m3.ha-l)

t h e s o i l moisture a t t h e f i e l d capacity FC A1 - l o s s e s caused by i n a c t i v e p e n e t r a t i o n through the s o i l p r o f i l e

(m3. ha-’)

A 2 - losses c a s e d by evaporation

( m3. ha-’ )

P

- p r e c i p i t a t i o n during t h e period of leaching (m3 .ha-’)

Ws - s u r p l u s moisture which remains i n s o i l

(m3. ha-’ )

a f t e r completed leaching

Losses caused by i n a c t i v e p e n e t r a t i o n through t h e s o i l p r o f i l e and evaporat i o n l o s s e s depend on t h e regime of leaching. The volume needed f o r t h e s o l u t i o n and washing away of s a l t s can be derived according t o Legostajev (1965) as

follows:

R1

=

100

. hs .

-

‘a . ‘0

(2.133)

s1

so

-

o r i g i n a l content of salts i n s o i l

(% of weight)

sa

-

admissible content of s a l t s i n t h e s o i l profile

(% of weight)

s1

-

amount of s a l t s which can be removed by 1 m3 of water

(% of weight)

b”, - u n i t hs

-

mss of s o i l

depth of t h e s o i l p r o f i l e i n question

.

(kg m-3)

Cm)

The q u a n t i t y of s a l t s which can be dissolved and washed away by 1 m3 of water depends on t h e water q u a l i t y , t h e chemical composition of t h e s a l t s , t h e s o i l s t r u c t u r e and t e x t u r e , t h e temperature and t h e groundwater l e v e l .

197 The q u a n t i t y of water needed f o r the supplementation of t h e s o i l m i s t u r e a t the f i e l d capacity should only be delivered i n w e l l drained s o i l s , i . e . when the water r e m i n i n g i n t h e s o i l l a y e r does not reach t h e f i e l d capacity. I n t h i s case

R2

=

100

. hs . b”, .

(FC

- Ido)

(m3)

FC - f i e l d capacity

(% of weight)

W - s o i l moisture before leaching

(% of weight)

0

(2.134)

The e f f e c t of leaching depends on t h e e f f i c i e n t drainage of the leaching water by means of a permeable s u b s o i l l a y e r or a drainage network. A f t e r leaching t h e water p o l l u t e d by leached s a l t s r e t u r n s t o the groundwater o r s u r f a c e resources. The l o s s which decreases t h e capacity of t h e water resources i s caused by evaporation and deep percolation. The i r r i g a t i n g schedule of leaching generally c o n s i s t s of s e v e r a l i r r i g a t i o n

r a t e s i n t‘ie off-season period. I t is useful t o apply t h e leaching r a t e i n the period of drought, a n d e s p e c i a l l y , during t h e drop i n t h e groundwater t a b l e , i n order t o preclude a n o v e r s a t u r a t i o n of t h e s o i l l a y e r and possible washing up of t h e s a l t s . A high groundwater t a b l e and i n s u f f i c i e n t drainage increases the evaporation l o s s e s and carries t h e s a l t up t o t h e s o i l surface. An excessive drop i n t h e g r o u n c h t e r t a b l e may considerably increase the losses caused by i n a c t i v e p e n e t r a t i o n through the s o i l p r o f i l e . Leaching bj7 groundwater decreases t h e groundwater t a b l e , thus deplenishing t h e groundwater resources, Leaching by s u r f a c e water can r e s u l t i n a recharging of t h e groundwater resources. But i n both cases t h e q u a l i t y of t h e groundwater i s negatively a f f e c t e d , e s p e c i a l l y when t h e r a t i o of leaching requirements t o t h e volume of groundwater resources i s high. 2.6.8

I r r i g a t i o n Losses

I t is p o s s i b l e to d i s t i n g u i s h t h e following water l o s s e s during i r r i g a t i o n

operation (Fig. 2.28): 1. Delivery losses ( l o s s e s of water d i v e r t e d f o r i r r i g a t i o n before applying t o i r r i g a t e d land) : (a)

canal and r e s e r v o i r seepage l o s s e s

(b) (c)

evaporation l o s s e s ,

leakage of g a t e s , unused s p i l l s and o t h e r escape l o s s e s ,

(d) unused water i n t h e i r r i g a t i o n network, 2. Farm l o s s e s ( l o s s e s of water applied t o i r r i g a t e d land): ( a ) supplementation of t h e s o i l moisture, not used by p l a n t s , (b) s u r f a c e and groundwater outflow of t h e unused water,

198 ( c ) deep p e r c o l a t i o n i n t o s u b s o i l l a y e r s , (d) i n e f f i c i e n t evaporation from t h e s o i l s u r f a c e and evaporation ir? the atmosphere during s p r i n k l e r i r r i g a t i o n , ( e ) evapotranspiration of weed p l a n t s , 3. Off-farm l o s s e s , i . e . by i r r i g a t i o n of a r e a s where i r r i g a t i o n i s not planned o r where i t is n o t f e a s i b l e . Farm and d e l i v e r y losses i n i r r i g a t i o n networks which have been overaltered arid a r e badly maintained a s w e l l a s not properly operated frequently exceed the consumption of p l a n t s . The l o s s e s can a l s o be caused by water wastage, i . e . by wrong o p e r a t i o n o r by using improper i r r i g a t i o n methods and techniques. They can be s i g n i f i c a n t l y limited by t e c h n i c a l and operational measures including proper maintenance, c o n t r o l l e d operation on t h e b a s i s of f l e x i b l e operating schedules, by t h e modernization and autcmatization of t h e operation and by the management of i r r i g a t i o n r a t e s on t h e b a s i s of t h e continuously measured agrohydrometeorological data and weather f o r e c a s t .

E vapovation

\

D I V E R T E D FOR RIVER

D y

APPLIE' FIELD

FLOW -Lorn

E V A POTR ANS PI RATION FROM CROPS Other evapotransnpiration from irrigated land

-

Evaporation river

Per c ol a ti o n Surface in-flow

1

E tf lue n t s

Fig. 2.28. Model of t h e i r r i g a t i o n return-flow system according t o Law and Denit (1972), completed. The c o e f f i c i e n t of water d e l i v e r y i . e . of t h e ed e f f i c i e n c y of t h e i r r i g a t i o n network, is expressed by t h e r a t i o of t h e amount of water delivered t o the

-%

fami f i e l d t o t h e water withdrawal

ed

=

+

m

=

'0

i

(2.135)

199

en - c o e f f i c i e n t of water d e l i v e r y R

-

a

amount of water delivered t o t h e farm field

(m3)

14 - water withdrawal

(m3 )

4,- d e l i v e r y losses ( l o s s e s i n t h e d e l i v e r y

(m3)

network) The c o e f f i c i e n t of t h e f i e l d e f f i c i e n c y ef i s expressed by t h e r a t i o of the amount of water a c t u a l l y consunled by the i r r i g a t e d p l a n t t o t h e amount of water delivered t o the farm f i e l d (2.136) ef - c o e f f i c i e n t of water a c t u a l l y consunied by the i r r i g a t e d p l a n t s

Af - farm l o s s e s

(m3 1

I t goes without saying t h a t t h e amount of water a c t u a l l y consumed should

correspond t o t h e i r r i g a t i o n requirements of t h e p l a n t s

Ra-

f 2 j=Pf. 1=1 =

(Eei

+ Rli

-d.;P;

1

- Wwi

-W .

g1

(m3.ha-’

per y e a r ) (2.137)

The t o t a l losses of i r r i g a t i o n water can be derived from t h e c o e f f i c i e n t of t h e t o t a l e f f i c i e n c y , i . e . from t h e r a t i o of water withdrawals t o t h e a c t u a l consumption of p l a n t s , corresponding t o t h e product of t h e c o e f f i c i e n t s of water d e l i v e r y and f i e l d e f f i c i e n c y et =

+

2.6.8.1

=

ed

.

ef

(2.138)

Delivery Losses

An i r r i g a t i o n d i s t r i b u t i o n system c o n s i s t s of open o r covered c a n a l s , cul-

v e r t s , p i p e l i n e s , d i t c h e s and corrugations ; water can be transported i n tanks, c i s t e r n s o r by combinations of a l l these p o s s i b i l i t i e s . Delivery losses depend m i n l y on t h e type and length of t h e d i s t r i b u t i o n system, on its equipment, operation and maintenance. The value of l o s s e s and the p o s s i b i l i t y of a n economic operation of t h e i r r i g a t i o n network depend on i t s design, which is interconnected with t h e irrig a t i o n method and on i t s s t a t e . Modem i r r i g a t i o n methods such as s p r i n k l e r o r t r i c k l e i r r i g a t i o n , which have smll farm l o s s e s , a r e o f t e n supplied from p i p e l i n e networks.

200 The p r e c i s i o n of p i p e l i n e s , the dimensional accuracy of t h e i r f i t t i n g s r e s u l t i n very low seepage and leakage l o s s e s i n t h i s type of delivery network. Seepage losses i n concrete pipes a r e veiy low and metal, asbestoscement and p l a s t i c pipes a r e almost without seepage. Nith regard t o t h e evaporat,ion l o s s e s of p i p e s , they a r e almost n i l under pressure operation and a r e a l s o

extrm.ely low during f r e e s u r f a c e flow, due t o

the high humidity i n s i d e . Higher l o s s e s may occur through t h e leakage of untight pipes under p r e s s u r e or during t h e operation of i n c o r r e c t l y e r e c t e d p o r t a b l e pipes.

TABLE 2.37 Method Spontaneous clogging Compacting Sprinkling with chemicals F l o a t i n g with clay o r loam Clay l a y e r Concrete, a s p h a l t membranes

Probable drop (%)

40 - 50 50 - 60 50 - 75 40 - 75 70 - 85 80

- 95

The impact of d i f f e r e n t methods of decreasing seepage losses i n unl'ined channels. The amount of water which remains i n t h e p i p e l i n e network is a l s o very small

compared w i t h t h a t i n t h e open channel network. Generally, losses i n t h e pipel i n e s of a n i r r i g a t i o n network a r e r e l a t i v e l y lower than those of t h e municipal water supply system. They should not exceed 3 - 5 % f o r small-scale networks c o n s i s t i n g of pipes with small diameters and not more than 8 - 10 % f o r larges c a l e networks and f o r p o r t a b l e ones. Water losses i n open channels a r e ccmparatively higher: they c o n s i s t mainly of seepage, leakage and o t h e r escape l o s s e s , which a r e r e l a t i v e l y bigger due t o the perviousness of the c o n s t r u c t i o n m a t e r i a l , low dimensiona1 accuracy, higher roughness and bigger cross s e c t i o n s . Seepage l o s s e s i n open channels depend (a) on t h e length of t h e wetted perimeter and t h e water depth, (b) on t h e hydraulic gz-adient and t h e roughness of t h e canal, which d e t e r mines t h e flaw v e l o c i t y , ( c ) on t h e bank and bottom l i n i n g , i . e . on i t s p e r v i m s n e s s , (Tab. 2.37). (d) on t h e water q u a l i t y , e s p e c i a l l y on t h e content of suspended matter, i t s g r a i n s i z e d i s t r i b u t i o n , which i n combination w i t h t h e f l m v e l o c i t y decides on the sedimentation r a t e and on t h e clogging of t h e pores, ( e ) on t h e s o i l p r o p e r t i e s of t h e bottom and banks, i.e. on t h e i r s a t u r a t i o n

201 and hydraulic conduct:ivity, ( f ) on t h e d i f f e r e n c e i n t h e water l e v e l a l t i t u d e and t h e groundwater t a b l e a 1t i tude , (g) on the d u r a t i o n of t h e operation and i t s schedule. The f o m u l a f o r seepage l o s s e s according t u Dairies and Wilson (1965) includes basic parameters only. The r e s u l t s of computations according t o o t h e r formulas, including rrrore e n t r y data influencing- seepage, do not produce more r e l i a b l e res u l t s . The problem i s t h e c0incidenc.e of t h e relevant e n t r y d a t a with t h e r e a l data of t h e p a r t i c u l a r c a s e . More p r e c i s e values of seepage can be determined by a n a l y t i c a l methods only o r by e l e c t r i c a l analogy, which is more r e l i a b l e f o r the s e l e c t i o n of alte-matives and t h e design of t h e i r r i g a t i o n network and f o r the r e l e v a n t economic a n a l y s i s . R e l i a b l e data on seepage i n a n e x i s t i q q network can be gained by measuring only. Delivery losses p e r 1 Ian from unprotected e a r t h canals p e r 1 km exceed 10 % of the discharge provided t h e operation is p e m n e n t and t h e discharges a r e r e l a t i v e l y lcw (belcw 0.1 m3 .s -1 ). I n t h e case of higher discharges, interrupted operation and pervious ground, t h e s e l o s s e s range between 10 and 20% of the discharge a t 1 km length, dropping t o h a l f t h i s value i n t h e case of permanent operation. These values can be used f o r a f i r s t o r i e n t a t i o n only: t h e problem of water savings by means of a change i n t h e operating schedule from continuous t o i t e r r u p t e d operation and vice versa i s complex and depends on l o c a l c o n d i t i o n s , and not cinly on t h e duration of t h e operation. Delivery l o s s e s i n open channels can be decreased by increasing t h e v e l o c i t y of flow, by minimizing t h e canal c r o s s s e c t i o n s , by optimizing i t s shape, and l i n i n g t h e banks and b o t t m of these canals. By lessening t h e roughness of t h e bottom and of t h e banks, i t i s p o s s i b l e t o reduce seepage not only because the increased v e l o c i t y of flow, but a l s o due t.0 t h e generally lmer perviousness of the f i n e m a t e r i a l s used f o r t h i s purpose. A l l these measures should be analyzed taking i n t o account t h e i n t e r r e l a t e d problems of canal operation, e.g. with a view t o t h e r e s u l t i n g waterlogging, e r o s i o n and sediment t r a n s p o r t problems. Evaporation losses of open channels i n humid a r e a s a r e r e l a t i v e l y kw, But i n semi-ari.d and a r i d a r e a ? t.he impact c f evaporation i s r e l a t i v e l y high. These l o s s e s can be reduced by operation a t n i g h t , which is f e a s i b l e only f o r relat i v e l y small networks t h a t can be operated f o r a j u s t a few hours p e r day. To reduce d e l i v e r y l o s s e s by t h i s i n t e r r u p t i o n of t h e operation during high evaporation r a t e s , seepage l o s s e s r e s u l t i n g from new f i l l i n g must not exceed evaporation l o s s e s during t h e period that was excluded from operation. I n t e r rupted operation reduces t h e t o t a l d e l i v e r y l o s s e s , providing that t h e seepage losses a r e r e l a t i v e l y low. A s u b s t a n t i a l decrease i n evaporation losses can be achieved by covering t h e c a n a l , by c o n s t r u c t i n g closed c u l v e r t s , o r by overshadowing i t s water t a b l e w i t h a p r o t e c t i n g canopy, a s w e l l a s by minimizing

2 02 the water table width by forming a semi-circular o r semi-eliptic o r rectangular cross section with a longer v e r t i c a l a x i s . Water losses through evapotranspiration, caused by the bank canopy, a r e negl i g i b l e i n h m i d areas only. I n semi-arid and a r i d countries, these losses m y play an important r o l e . Nevertheless , the protecting canopy mkes i t possible t o increase the slope of the banks and overshadow the water table, thus limiting the evaporation frcm open water surfaces. This positive impact of the canopy m y prove prevailing, a l s o having a favourable influence on the microclimte. Evaporation, seepage, leakage as well as waste water and other losses should be considered a s losses i n the balance of water resources and needs, i f not recovered i n streams o r under the ground. These losses may produce problems of oversaturation, waterlogging and s a l i n i t y , thus decreasing not only the yields but a l s o the s o i l f e r t i l i t y and causing environmental problems as well as sanitary hazards.

2.6.8.2

Farm Losses The selection of the i r r i g a t i o n rLethod deperrds on cultivation practices,

which a r e closely interconnected with the crop pattern and plant species. Modem methods of i r r i g a t i o n are characterized by substantially lower farm losses, but a l s o by lower delivery losses, because modern i r r i g a t i o n practices require modern nlethods of water conveyance. These methods a l s o require higher investments and operation costs ; furthermore, they a r e energy-consuming

, as

we1 1 as frequently beir.g labourdenlarding ,

thus requiring s k i l l e d workers. The change from t r a d i t i o n a l i r r i g a t i o n t o modem i r r i g a t i o n often requires a basic change i n cultivation practices, replacing primitive labour by s k i l l e d i n s t a l l a t i o n and operation. Local forces m y not always be available t o overcome the gap i n nlanpmer needs. Farm losses depend not only on the i r r i g a t i o n method, but a l s o on the technii t s control and regular checking, as well as on the

c a l level of i t s operation

r e l - i a b i l i t y of the mnpower or of the automatic equipment. A t the beginning of the application of the i r r i g a t i o n r a t e water losses caused by supplementation of the s o i l moisture can occur, which cannot be recovered by the suction pressure of the plants. These losses can be substantial, especially i n dry heavy s o i l s . Another farm loss is the percolation i n t o subs o i l layers which have no capillary interconnection with the s o i l p r o f i l e . This percolation l o s s , which recharges the groundwater resources, can only be determined by local metering, Losses through overland flow occur during overirrigation, namely a f t e r the accirmulation of the surplus water on the s o i l surface, unless the subsequent. runoff can be u t i l i z e d f o r the effective i r r i g a t i o n of the adjacent l a d . The accumulation of water on the land surface, which i s a l s o caused by water-logging,

2 03

increases t h e evaporation l o s s e s . The value of evaporztion l o s s e s depends on t h e a r e a of t h e water accumulated on t h e land s u r f a c e . During b a s i n , graded-border o r contour-ditch i r r i g a t i o n , the whole i r r i g a t e d area is flooded and unproductive evaporation occurs from the e n t i r e i r r i g a t e d s t r i p . During furrow o r corrugation i r r i g a t i o n , the flooded s u r f a c e i s remarlobly r e s t r i c t e d , r e s u l t i n g i n a s u b s t a n t i a l decrease i n evapor a t i o n l o s s e s . This depends on t h e d e n s i t y and width of t h e furrows, and on the soil structure

.

The flooding of t h e e n t i r e s t r i p can a l s o occur during s p r i n k l e r i r r i g a t i o n , by exceeding t h e a p p r o p r i a t e i r r i g a t i o n r a t e . The e f f i c i e n c y of s p r i n k l e r irri-

g a t i o n depends on t h e harmony of the i r r i g a t i o n r a t e with t h e s u c t i o n pressure of s o i l , which decreases the evaporation. Losses during s p r i n k l e r i r r i g a t i o n a r e a l s o caused by t h e i r r i g a t i o n of unproductive land and by evaporation i n t h e atmosphere. The value of evaporation losses i n t h e atmosphere depends on t h e temperature and a i r humidity, on t h e wind v e l o c i t y , on t h e s i z e of t h e water drops and t h e duration of the penetration through t h e atmosphere. Evaporation l o s s e s during wind of v e l o c i t y 4 m . s -1 exceed these recorded during calm periods by four times and more. When t h e wind v e l o c i t y does n o t exceed 1 t o 1.5 m.s-', t h e t o t a l f i e l d l o s s e s through sprinkl e r i r r i g a t i o n a r e lower than those during t r a d i t i o n a l i r r i g a t i o n methods, even in arid areas. The s i z e of t h e water drops and t h e duration of t h e i r penetration through the atmosphere depend on t h e operation pressure of t h e s p r i n k l e r , on the shape and diameter of t h e nozzles, i.e. on t h e type of t h e s p r i n k l e r , as w e l l a s on the arrangement of t h e i r r i g a t i o n r a t e and on t h e s p r i n k l i n g i n t e n s i t y , which should be harmonized with t h e given climatological conditions. Operation should be c o n t r o l l e d according t o t h e meteorological conditions, i . e . t h e conditions of t h e l o c a l microclimate; e . g . a i r temperature a t night a r e lower, t h e wind v e l o c i t y i s milder and r e l a t i v e humidity higher. These favourable conditions usually r e s u l t i n a 10 t o 15% decrease i n evaporation losses i n comparison with s p r i n k l i n g operation i n t h e morning o r afternoon. The r e l a t i v e evaporation l o s s e s decrease with t h e increase i n t h e i r r i g a t i o n r a t e , due t o t h e influence of t h e humid microclimate formed by t h i s operation provided the a c t u a l i n f i l t r a t i o n r a t e i s not exceeded. Maximum i r r i g a t i o n e f f i c i e n c y is achieved by d r i p l t r i c k l e i r r i g a t i o n . This high e f f i c i e n c y f o l l m s from t h e l i m i t a t i o n of t h e a r e a i r r i g a t e d t o t h e irmned i a t e v i c i n i t y of t h e p l a n t , c o n t r o l l e d by its s u c t i o n pressure. In t h i s way not only a r e evaporation l o s s e s e f f e c t i v e l y r e s t r i c t e d , but p e r c o l a t i o n i n t o unproductive s u b s o i l l a y e r s is a l s o correspondingly reduced. This i r r i g a t i o n method, a l s o used t o add f e r t i l i z e r s , i s characterized by high investment and operation c o s t s and t h e r e f o r e i s f e a s i b l e f o r f r u i t t r e e s

204 and shrubs and f o r s e l e c t e d types of v e g e t a b l e s , such a s tomatoes, peas, lett u c e , cucumbers, gourds, aubergines , water-melons , peppers e t c . The advantages of t r i c k l e i r r i g a t i o n include i n p a r t i c u l a r : (a) w a t e r s a v i n g s , r e s u l t i n g i n a 10 t o 20% i n c r e a s e i n y i e l d and, under s p e c i a l c o n d i t i o n s , even by a high 60% and h i g h e r i n c r e a s e without any rise i n water requirements o r water consumption, (b) t h e p o s s i b i l i t y of a l s o u s i n g low q u a l i t y water f c r i r r i g a t i o n , i . e . b r a c k i s h and even sea w a t e r , because i n t h e course of t h e t r i c k l e i r r i g a t i o n

the s o i l and p l a n t a c c e p t t h e minimum p h y s i o l o g i c a l l y indispensable water quant i t y , which consequently restricts t h e i n p u t of s a l t s . T r i c k l e i r r i g a t i o n with low q u a l i t y water r e q u i r e s a p p r o p r i a t e o p e r a t i o n including r e g u l a r leaching. ( c ) t h e p o s s i b i l i t y of f e r t i l i z i n g i r r i g a t i o n , which can be dosed depending on t h e a c t u a l growing s t a g e and nutriment requirements of t h e r e l e v a n t p l a n t species, ( d ) l a r g e r s i z e , h i g h e r q u a l i t y and b e t t e r colour of p l a n t s , r e s t r i c t e d occurrence of p e s t s , weeds and p l a n t d i s e a s e s , (e) 2.6.9

s h o r t e n i n g of t h e v e g e t a t i o n period. Water f o r Livestock and Processing

Livestock breeding i s a n important component i n t h e balance of biogeochemic a l c y c l e s . Durirg l i v e s t o c k breeding and a g r i c u l t u r a l processing, water i s used ( a ) t o water c a t t l e ( i n c l u d i n g p r e s s u r e cooking, d i l u t i o n of fodder mixtures e t c . ) (b) (c)

a s s e r v i c e water ( f o r waste d i s p o s a l , washing and cleaning)

as process water

( d ) a s d r i n k i n g w a t e r ( f o r newly born c a l v e s and sucking-pigs, nnel e t c . )

f o r perso-

With regard t o t h e q u a l i t y o f water f o r l i v e s t o c k , t h e r e l e v a n t requirements a r e r e l a t i v e l y lower i n comparison w i t h t h e d r i n k i n g water q u a l i t y , e s p e c i a l l y i n term of t h e chemical and b a c t e r i o l o g i c a l i n d i c a t o r s . Rut t h e r e a c t i o n of d i f f e r e n t s p e c i e s of domestic animals v a r i e s and depends on t h e i r age. (Tab.

2.38, 2.39). Horses r e q u i r e high water q u a l i t y , w h i l e sheep can take r e l a t i v e l y low q u a l i -

ty. The q u a l i t y requirements of newly born and sucking animals a r e r e l a t i v e l y high, r e s u l t i n g i n t h e u s e of d r i n k i n g water t o supply young calves and sucking pigs. The h e a l t h s t a g e and y i e l d of l i v e s t o c k and p o u l t r y depends on t h e q u a l i t y and q u a n t i t y of t h e water d e l i v e r e d . A 30% d e c r e a s e i n water supply i n large-

scale breeding r e s u l t s f o r example i n a 40% decrease i n milk y i e l d and i n a 30% decrease i n Tork y i e l d .

205 TABLE 2.38

Indicator

Livestock

Man mass supply

individual ~

Oxidizing

mg.02.1-1

Sulpha tes

mg. 1-1

5

3

< 450

Bacteria c o l i 0 p e r mezophyllic p e r ml psychrophyllic per ml 0 Temperature (minimum) C

<

10 m l

<

'

25

< < 500

< < 200

500 6

50 10 m l 100

100 m l 20

< 2000

3

8-12

8-12

10a), 14b) Differences i n water q u a l i t y requirements of drinking w i t e r f o r m n and livestock. a ) f o r c a l v e s , b) f o r sucking-pigs. For newly born calves drinking water standards and minimum temperature 25OC. TABLE 2.39

Evaporation residium

Calves

< 2400 mg.1-1 < 1800

Pigs

<

cows

Sucking-pigs Horses Foals Sheep

Lamb

1200

< 1000 < 1000 < 1000 < 5000 < 3000

Chlorides

Sulphates

<

600 mg.1-I 400 400 350

< 800 mg.1-l < 600 < 600

400

< 500 < 500

< < <

< 350 < 2000 < 1500

<

500

( 2400

< 1700

I n d i c a t o r s , c h a r a c t e r i s i n g t h e s e n s i t i v i t y of d i f f e r e n t l i v e s t o c k species t o water q u a l i t y requirements and t h e f e a s i b i l i t y of l i v e s t o c k breeding under d i f f e r e n t water q u a l i t y conditions. The requirements of watering l i v e s t o c k and of s e r v i c e water n e c e s s a r i l y de-

pend on t h e breeding technology. Plodern breeding technologies r e s u l t i n a 50 t o 100% increase i n water requirenents compared with smll-scale breeding, because higher s a n i t a r y standards a r e necessary t o cope with the increased proba b i l i t y of diseases due t o high degree of c a t t l e accumulation. Furthermore, replacing human labour by mechanical processes r e s u l t s i n an increase i n service water requirements: remwing l i t t e r r e s u l t s i n a 20% increase i n water requirements (Tab. 2.40). The t o t a l d a i l y water requirements of l i v e s t o c k production c o n s i s t of w a t e r ing and processing a s w e l l a s s e r v i c e water f o r waste d i s p o s a l , washing and cleaning :

206

i=l ni

. r . + Rp +

k-1

%

3 (m p e r day)

. ‘k

(2.139)

R

=

R b

-

t o t a l d a i l y water requirements of a c a t t l e breeding farin

ri

-

s p e c i f i c requirements p e r head of c a t t l e o r poultry

1

3 (m p e r PC)

n . - number of heads i n category i

(PC)

R - d a i l y requirements of processing water,

(m 3 per day)

Ak - area of r e l e v a n t operational space k

(m2 ) 3

i f not included i n s p e c i f i c requirements per head

rk

-

s p e c i f i c water requirement per square meter

(m

2 per m )

TABLE 2.40

Species

Water requirements p e r pc and day Average Maximum

Ex r e n e n t s . liqud solid (1 p e r day) (kg per day)

Livestock: under f a t t e n i n g

10-40a)

60

10

30

milk c m s

15-60a) 15 40

140 20 60

20 2

35 5

60 8 4 1,5-15

80 10 6 25

8

9

calves horses mares and s t a l l i o n s sheep lambs f a t t e n e d hogs Poultry and small animals : Hens

0, 25b)-0 ,75‘)

1,5d)

Broilers Geese and ducks

0,25b) 192

0,35 195

Guinea-hens and turkeys Rabbits

038

039

3

5

Water requirements f o r l i v e s t o c k and poultry breeding a ) lcwer value piped water, higher one r i n s i n g system, b) d r i p and s e l f - f i l l i n g drinking bowls, c ) flow drinking bowls, d) during long s m e r days

207 The a c t u a l requirements f o r watering depend on t h e season, temperature, durat i o n of the d a y l i g h t , on t h e r e a l weight of t h e r e l e v a n t s p e c i e s , and on t h e p a r t i c u l a r breeding p r a c t i c e s ( s t a b l e and walk, hen-roost o r run, outdoor breeding, small-scale o r large-scale, type of equipment e t c . ) . A remarkable fluctuat i o n i n requirements depending on t h e d u r a t i o n of t h e daylight occurs e s p e c i a l l y on poultry farms. The nBximum d a i l y and per hour requirements can be derived with t h e a i d of simple equations

3

R d = R b . kd Rh = - z1; T . Rd

. Ij,

(rn per day) (m3 per hour)

(2.140) (2.141)

Rb - t o t a l d a i l y water requirements Rd - maximum d a i l y water requirements

Rh - maximum per hour requirements

- 2.4) 3 (m per hour)

$-

(Ij,=

kd - c o e f f i c i e n t of d a i l y f l u c t u a t i o n

c o e f f i c i e n t of per hour f l u c t u a t i o n

(kd = 1.6

1.8 - 3.5)

Process water i n a g r i c u l t u r e , a s i n industry, includes a l l water needed f o r (a)

processing (including milk production)

(b)

hydraulic t r a n s p o r t (of manure, potatoes, b e e t s , c e r e a l s e t c . )

( c ) cooling (of milk and o t h e r products) and a i r conditioning, (d) b o i l i n g and h e a t i n g , ( e ) s o r t i n g , washing, r i n s i n g and cleaning (of potatoes, vegetables, f r u i t s , c e r e a l s , meat e t c . ) Water i n a z r i c u l t u r e is used e i t h e r a s matter e n t e r i n g t h e product, a s mtter which canes i n t o d i r e c t contact with t h e intermediate or f i n a l product o r a s a cooling o r h e a t c a r r y i n g medium. Relevant water q u a l i t y requirements can be, t h e r e f o r e , c l a s s i f i e d i n t h e same manner a s t h e i n d u s t r i a l water use. 2.6.10

Water P o l l u t i o n from A g r i c u l t u r a l Production There a r e t h r e e main groups of p o l l u t o r s i n a g r i c u l t u r a l production:

( a ) p o l l u t i o n f r a n p l a n t production ( m i n l y a r e a l ) : washing away of t h e eroded s o i l p a r t i c l e s , applied and s t o r e d f e r t i l i z e r s , wastage of p l a n t products, drainage waters and waste waters f r a n i r r i g a t i o n polluted by e x t r a c t i o n of s a l t s due t o o v e r i r r i g a t i o n e t c . , (b) p o l l u t i o n from l i v e s t o c k and poultry breeding (mainly l o c a l ) : wastes from small and large-scale c a t t l e , sheep and poultry breeding, including a r e a l

p o l l u t i o n from c a t t l e walks, hen runs and p a s t u r e s , escape of dung water and waste water from s t a b l e s , escape of s i l a g e e t c . ,

208 ( c ) p o l l u t i o n from a g r i c u l t u r a l processing ( m i n l y l o c a l ) : waste water from processing, d a i r i e s , from washing of a g r i c u l t u r a l machines, escapes of o i l and o i l products, s t o r e d agrochemicals e t c . Agrochemicals can be categorized according t o t h e i r s o l u b i l i t y , t o x i c i t y , p o s s i b i l i t y of decomposition o r accumulation i n organic m t t e r , and t h e i r migr a t i o n p r o p e r t i e s , which influence t h e water q u a l i t y (Tab. 2.41, 2 . 4 2 ) . TABLE 2.41

Characteristic

Lethal dose f o r warmblooded animls a)

C o e f f i c i e n t of accumulation f o r warmof a a m t i c blooded organisms animals

*k

1 slightly dangerous 2 dangerous

3 highly

Kk

>loo0

>5

201-1000 5 1-1 000

4-5 1-3

S t a b i l i t y b) i n s o i l i n water (days)

K"

(50

(30

(5

51- 200 1-6 month 6-10 1000 0,5-2 years 11-30

dangerous

< 50

4 extremely dangerous

C l a s s i f i c a t i o n of chemicals, e s p e c i a l l y p e s t i c i d e s , a f t e r t h e i r threatening of s u r f a c e and groundwater according t o the COMECON proposal f o r standard ( 1 9 8 1 ) . a ) mg p e r kg of weight, peroneal dosage b ) d u r a t i o n of degradation on harmless c o n s t i t u e n t s K = LD50 chronica - c o e f f i c i e n t of accumulation f o r warm-blooded animals k ID5o a c u t a

Average dose f o r warm-blooded animal, peroneal dosage, mg p e r kg of weight:

ID5o chronica LD50 acuta

-

by repeated dosage by s i n g l e dosage

C

K

n

=

2 Cv

c o e f f i c i e n t of accumulation i n a q u a t i c organisms

C - concentration i n a q u a t i c organisms

g Cv - concentration i n water

The q u a n t i t y of excrements from l i v e s t o c k and poultry breeding can be derived from t h e weight of t h e relevant animal s p e c i e s . The r a t i o of t h e d a i l y production of excrements f l u c t u a t e s between 3.6 and 10% of the given weight. Poultry is characterized by lower, pigs by higher values. The d a i l y average production of l i q u i d excrements rises almost t h r e e times, and the maximum d a i l y production t o 250%, when water d e l i v e r y by c i s t e r n s i s replaced by a waterworks.

2 09 The p r e v a i l i n g p o l l u t i o n of water resources by a g r i c u l t u r a l production dcpends on l o c a l conditions and so any of t h e mentioned t h r e e groups of p o l l u t i o n m y predominate i n a given l o c a l i t y . IJnder conditions of i n t e n s i v e p l a n t production the a r e a l mineral and s y n t h e t i c p o l l u t i o n by f e r t i l i z e r s and p e s t i c i d e s generally predominates. The influence of t h i s a r e a l p o l l u t i o n may s u b s t a n t i a l l y exceed (up t o s e v e r a l times) t h e t o t a l p o l l u t i o n of water resources caused by i n d u s t r i a l and municipal p o l l u t i o n . TABLE 2.42

Class C h a r a c t e r i s t i c s

Application

Species of p e s t i c i d e s

0

Non-poisonous

without l i m i t a t i o n

sulphur fungicides (except barium polysulfide) , zincous oxide, i r o n sulphate

1

S 1igh t ly dangerous

Application limited i n p r o t e c t i o n zones f o r drinking water resources

Zincous s u l p h a t e , zonepion a c i d , hexachlorbenzol, a c i d s u b s t i t u t e d by halogens, fung i c i d e s with copper content, eneine o i l

2

Dangerous ( e a s i l y degradable, nonaccumulative)

Application proh i b i t e d i n protect i o n zones f o r surface resources and r e s t r i c t e d i n prot e c t i o n zones f o r groundwater resources used f o r municipal and r u r a l water S U D D ~ V

d e r i v a t i v e s of ptienoxiacid, carbamate, t r i a z i n , dithiophosphorousacid (except met i d a t ion) , h e t e r o c y c l i c fungicides, amid a c i d s , a n a l i d e s , t r i c h l o r f o n , dic h l o r f o s , f e n y t r i o n , fenthion, bromfos, l,Lt-dichlorpropane, zincous phosphide , baryum DolvsulDhide

3

Application proHighly dangerous (poisonous, e a s i l y h i b i t e d i n protecdegradable, accut i n g zones f o r surf a c e resources, mulat i v e ) exceptional usage i n p r o t e c t i n g zones f o r groundwater resources used f o r public water supply

d e r i v a t i v e s of b i p y r i d i n , morkaptan (except f o r a t ) , o t h e r chlorinated hydrocarbons (except endosulphane), carbamin a c i d , d e r i v a t i v e s of ureas, a l l combinated herbicides

4

Ex t renie 1y dangerous

nitroderivatives , derivatives of dinitrophenol, f o r a t s , endosulphane? poisonous g r a i n , matter containing mercury Hg o r a r s e n i c As

~

S t r i c t prohibition of usage i n protecting zvnes f o r water resources

C l a s s i f i c a t i o n of chemicals used during p l a n t production according t o t h e i r s u i t a b i l i t y f o r a p p l i c a t i o n i n p u b l i c water supply p r o t e c t i n g zones.

The production and physiological processes of p l a n t production take place i n a pervious s o i l environment. P r e c i p i t a t i o n and s u r f a c e i r r i g a t i o n washes away

soil p a r t i c l e s and agrochemicals, e s p e c i a l l y under conditions of large-scale production, thus causing t h e i r leaching and e x t r a c t i o n and the consequent con-

210 tamination of s u r f a c e and groundwater resources. The inconsistency of f e r t i l i z e r and p e s t i c i d e a p p l i c a t i o n with p r o t e c t i n g water resources occurs when these agrochendcals escape from t h e root zone of the p l a n t s . P l a n t s accept s e l e c t e d chemical elements only, e s p e c i a l l y nitrogen N, potassiun K

, phosphorus

P

-

p a r t i a l l y a l s o calcium Ca,

magnesiuni Mg and

microbioelements. They do not accept any elements which are p r e s e n t i n t h e s o i l i n surplus. The aim of maximizing a g r i c u l t u r a l y i e l d s with a minimum of human labour (unfortunately coupled with a lack of technological d i s c i p l i n e ) leads t o a n overapplication of agrochemicals. The a p p l i c a t i o n r a t e s of chemicals frequently exceed 1.5 t o 2 times and more t h e output of r e l e v a n t bioelements during p l a n t production. The contamination of water resources by i n t e n s i v e p l a n t production

is a problem of balancing t h e nutriment input and output. The r e s u l t i n g s u r f a c e and groiindwater p o l l u t i o n i n d i c a t e s not only overapplication and improper applic a t i o n p r a c t i c e s , but a l s o an ilneconomic tt7ay of production, i . c . t h e wastage of agrochemicals

.

211 Chapter 3

WATER SYSEMS AND WATER BAUNCE

CXQACTERISTICSOF STJRFACE AND GROINDIJATER RESOURCES

3.1

The development of water resources and water management, i . e . management of a l l a c t i v i t i e s which influence t h e l o c a t i o n and t h e course of water occurrence, q u a l i t y and u t i l i z a t i o n , s e r v e s t o s a t i s f y s o c i a l requirements by water a v a i l a b i l i t y , both depending on n a t u r a l , h i s t o r i c a l and economic f a c t o r s . The relevant water development s t a g e can be characterized by t h e innovative u t i l i z a t i o n of water i n t h e key branch of the developing economic s t r u c t u r e (Tab. 3.1).

TABLE 3.1

Stage

Innovation C h a r a c t e r i s t i c s ‘prevailing u t i l i z a t i o n )

Innovation Tool (means )

Period i n Europe

1. .

individual consumption

2.

c o l l e c t i v e usage

jug well

3. 4.

r i v e r navigation

boat

irrigation

i r r i g a t i o n canal

? 5 . m i l .B .C . 3 . m i l .R .C. 2 . m i l .R .C.

5.

humn power

bucket wheel

6. 7.

water power

water wheel

1O.c.A.D.

f i s h breeding minicipal water supply

f i s h pond p i p e l i n e networks

10.-15 . c . A . D . 12.-16.c.A.D.

mine drainage

pump, driven gears

15.-18.c.A.D.

inland navigation i n d u s t r i a l development

canals

11.

s t e a m engines

16.-19.c .A.D. 19. c.A.D.

12.

hydropmer

water turbines

19.c.A.D.

13. 14.

mss usage

reservoirs

19.-20.c.A.D.

multipurpose usage

mu1 tipuf-pose res ervoi rs

20.c.A.D.

15.

large-scale usage

water s y s t e m

end of the 20. c .A.D.

16.

r a t i o n a l usage

wa ter-saving

21 .c .A.D.

8. 9. 10.

Characteris t i c s t a g e s of water resources development.

Surface water and groundwater a r e frequently developed a s separate resources. The reason f o r t h i s r e s t s i n the h i s t o r i c a l and economic conditions, as well as i n t h e i r physical d i v e r s i t y . This d i v e r s i t y r e q u i r e s not only d i f f e r e n t modes of u t i l i z a t i o n but a l s o d i v e r s e methods of i n v e s t i n a t i o n .

Surface water i s

212 used and irlvpstigated a s a dynamic resource depending on n a t u r a l f a c t o r s , and erorindwater a s a renewable raw m a t e r i a l . This r e s u l t s i n d i f f e r e n t degrees of cognizance of t h e i r physical parameters, having a feedback on t h e i r u t i l i zation. Surface water resources a r e characterized by t h e i r shape and s i z e , i . e . Aquifers, permeable geological formations volume (m3 ) and discharge (m3.s-’). containing water, a r e characterized n o t only by t h e i r shape and s i z e , but a l s o by t h e i r e f f e c t i v e p o r o s i t y . The e f f e c t i v e p o r o s i t y i s usually expressed a s a percentage and corresponds t o t h e s p e c i f i c y i e l d , t h e volume of water which can be removed by t h e f o r c e of g r a v i t y . I n a d d i t i o n t o t h i s , an a q u i f e r has a s p e c i f i c r e t e n t i o n and contains a cert a i n amount of water governed by forces o t h e r than g r a v i t y . The sum of t h e s p e c i f i c r e t e n t i o n and t h e s p e c i f i c y i e l d corresponds t o t h e t o t a l p o r o s i t y . The c o e f f i c i e n t of permeability or hydraulic conductivity kf i s defined a s a q u a n t i t y of water flowing i n one u n i t of time through a f a c e of u n i t area ( n ~ ~ . m - * . s - ~ : under a d r i v i n g f o r c e of one u n i t of hydraulic head change per

u n i t length. I t depends upon t h e p o r o s i t y : Upon g r a i n s i z e , shape and d i s t r i bution of pores, and compaction of t h e f o r m t i o n . The product of the hydraulic conductivity and t h e s a t u r a t e d thickness i s t h e transmissivity

Th k = j

h

kf

.

(m2 .s -1 )

dz

13.1)

- s a t u r a t e d thickness

This value c h a r a c t e r i z e s unconfined a q u i f e r s . A confined ( a r t e s i a n ) a q u i f e r

is characterized by t h e s t o r a g e c o e f f i c i e n t o r s t o r a t i v i t y S . This s t o r a t i v i t y is dimensionless and corresponds t o t h e volume of water released from the a q u i f e r ( o r taken i n t o s t o r a g e ) p e r u n i t s u r f a c e area of a q u i f e r and u n i t change of t h e piezometric head (m3 .m-2 .m-”\

,.

Hydraulic phenomena should be assessed over a long period of time on t h e basis of p r o b a b i l i t y . The l i k e l i h o o d of t h e i r recurrence i s e s t a b l i s h e d without reference t o any s p e c i f i c time i n t e r v a l . Reservoirs and a q u i f e r s modify t h e d i s t r i b u t i o n of water resources i n time by accumulating water during periods of excess flow and by augmenting n a t u r a l discharges during periods of low flow. Their e f f e c t can be c h a r a c t e r i z e d by t h e storage c o e f f i c i e n t

,

i . e . by t h e r a t i o of t h e s t o r a g e capacity of t h e r e s e r v o i r o r t h e volume of i n t e r s t i c e s forming t h e e f f e c t i v e poro:;ity o f t h e a q u i f e r and t h e long-term mean t o t a l annual flow/annual recharge.

p-

V

P Qa

(3.2)

2 13

ve - useful

storage capacity (volume of effective pores)

-

Qa

long-term mean t o t a l annual flow (long-term mean natural recharge)

<m3>

(m 3 per annum)

The development of water resources f o r maximum u t i l i z a t i o n requires the coordination of surface and groundwater management. Aquifers should be managed in the same manner as surface reservoirs. Depending on the relation between the storage capacity, the fluctuation of natural discharges and water requirements , flow regulation is confined t o seasonal redistribution and/or t o betweenyear regulation t o s a t i s f y water requirements during years with insufficient water flow. The guaranteed delivery

of a reservoir i s the r a t i o of the minimum dis-

charge secured by the reservoir t o the long-term average yearly (monthly, seasonal) discharge

(3.3)

%in

- minimum

(m 3 .s -1 )

Qa

-

(m .s

(yearly, monthly seasonal) discharge secured by the reservoir

average natural discharge

3 -1

1

The r a t i o of the surface y i e l d (m3 per annum) t o the average annual recharge

(m3 per annum) of the aquifer expresses the similar characteristics of the groundwater resources.

3.2

SAFE YIELD Unlike other mineral resources, water resources form a continuous flow which

is renewed within the natural hydrologic cycle. Man uses water i n t h a t p a r t of its hydrologic cycle which corresponds t o the flow of water over the land masses. Any u t i l i z a t i o n of water changes the course of t h i s cycle quantitatively

and qualitatively, and a l s o influences the r a t e of the relevant hydroloRica1 processes (recharge). Various attempts have been made (see paragraph 5.5) t o influence the hydrologic cycle and t o increase the quantity of usable water resources. When corn piling water balances a d i s t i n c t i o n has t o be made between - the t r a d i t i o n a l , conventional water uses and

-

the non-conventional uses of water. Water resources a r e dynamic and, therefore, the interrelationships between

surface and groundwater r e s t r i c t the number of categories which can be treated separately f o r the compilation of water balances: Through an accumulation of

214 t h e dynamic component on the s u r f a c e o r under t h e ground, t h e s t a t i c stock i s formed t o supplement the lack of t h e dynamic ccmponents, i f t h e need a r i s e s (Tab. 3 . 2 ) . TABLE 3.2

Component

Physical i n t e r pretation

Dimension

Static

volume

m

Dynamic

d is char ge (flow!

m .s

3

3

Definition

h u n t of water on t h e s u r f a c e o r under t h e ground, i n the given water management mi t , subsequently recharged -1

Amount of water leaving t h e r e l e v a n t water mnagement u n i t during a eiven u n i t of time

Basic i n t e r p r e t a t i o n of q u a n t i t a t i v e a s p e c t s of water resources i n a defined water management u n i t . I n t e r p r e t e d i n t h i s way, t h e s u r f a c e water resources c o n s i s t of two p a r t s : t h e f i r s t o r i g i n a t i n g from p r e c i p i t a t i o n and groundwater, t h e second coming from o t h e r water management u n i t s . The withdrawn water is p a r t i a l l y replenished by increased i n p u t of groundwater and reduced evaporation caused by t h e decrease i n water level. The e x p l o i t e d groundwater resources of a given t e r r i t o r y a r e replenished by increased i n f i l t r a t i o n from neighbouring a q u i f e r s , by increased i n f i l t r a t i o n from s u r f a c e w a t e r s , a s well a s by increased i n f i l t r a t i o n a f t e r r a i n f a l l and reduced evaporation a s ground water l e v e l s i n k s . The s a f e y i e l d of an a q u i f e r

is defined a s t h e amount of water which can be withdrawn annually from the a q u i f e r and which is replenished n a t u r a l l y , without bringing about some undes i r e d environmental

l e g a l o r o t h e r r e s u l t . To remove some of t h e ambiguity i n

meaning of t h i s term, t h e American Society of C i v i l Engineers (1961) defined four concepts of y i e l d a s follows: (a, Maximum s u s t a i n e d y i e l d i s t h e maximum r a t e a t which water can be withdrawn p e r e n i a l l y from a p a r t i c u l a r source. ( b ) Permissive s u s t a i n e d y i e l d i s the maximum r a t e a t which water can economically and l e g a l l y be withdrawn p e r e n i a l l y from a p a r t i c u l a r source f o r benef i c i a l purposes without bringing about some undesired r e s u l t . ( c ) Maximm mining y i e l d is the t o t a l volume of water i n s t o r a g e t h a t can be e x t r a c t e d and u t i l i z e d . ( d ) Permissive mining y i e l d i s t h e m a x i m volume of water i n storage t h a t economically and l e g a l l y be e x t r a c t e d and used f o r b e n e f i c i a l purposes, can without b r i n g i n g about some undesired r e s u l t .

215 I n a s s e s s i n g w a t e r resources a d i s t i n c t i o n has t o be made between n a t u r a l and u s a b l e water r e s o u r c e s . Natural water resources a r e , on average over a period of y e a r s , equal t o t h e mean multi-annual runoff from the defined water management u n i t , i . e . t o t h e volume of t h e n a t u r a l replenishment. The usable water resources of t h e given w a t e r management u n i t a r e c h a r a c t e r i z e d by t h e amiint o f water i n a longer time u n i t l m3 per y e a r ) o r by t h e flow-rate (m3.s-'

),

which can, with a n adequate degree of c e r t a i n t y , continuously supply

t h e r e l e v a n t water u s e r s . For a p r e c i s e assessment of u s a b l e water resoiirces, t h e following f a c t o r s shotild be taken i n t o accoiint, a s they infliience t h e n a t u r a l recharge r a t e : (a'\ t h e a d d i t i o n a l recharge caused hy t h e lowerinp of t h e water t a b l e : a d d i t i o n a l i n f i l t r a t i o n of r a i n w a t e r , decrease i n evaporation, i n c r e a s e o r redriction i n t h e groundwater inflow i n t o water c o u r s e s , i n f i l t r a t i o n from adjoining aquifers e t c . %'

anthropogenetic infliience, caused by land and water development, water

u t i l i z a t i o n e t c . and e s p e c i a l l v by r e t i i m flow. Taking i n t o account t h e natiiral a v a i l a b i l i t y of water and t h e t e c h n i c a l and economic l i m i t a t i o n s f o r iiicreasinp i t s supplv, water v i e l d , t h e aimunt of water which can be withdrawn from t h e water r e s o u r c e , has d i f f e r e n t q u a l i t i e s : Natiiral y i e l d i s t h e aniount of water

(I:?p e r

w a r ) which is supplied by t h e

water resoiirce t h a t is n o t influenced by anthropogenetic a c t i v i t i e s . The n a t u r a l y i e l d of s i i r f a c e resources corresponds t o n a t u r a l d i s c h a r g e s . I t s minimum value

i s , t h e r e f o r e , t h e niinimimi n a t u r a l d i s c h a r g e Qinin. The n a t u r a l y i e l d of groundwater resoiirces , t h e maximum s u s t a i n e d v i e l d , corresponds t o t h e n a t u r a l recharge and enables w a t e r withdrawals which do not d e c r e a s e n a t u r a l groundwater depo-

s i t s i n t h e long tmn. T h e o r e t i c a l y i e l d is t h e anlount of water

(ni

3 p e r \Tear) which i t would be

p o s s i b l e t o harness i n t h e long term bv niodifvinp t h e occiirrence o f water i n the long term, namely through s t o r a g e , a r t i f i c i a l i n f i l t r a t i o n and o v e r d r a f t of groiiiidwnter. The t h e o r e t i c a l v i e l d of a s i r f a c e resoiirce corresponds t o t h e average long-tenn anririal n i n o f f . The t h e o r e t i c a l s u s t a i n e d v i e l d o f a gmundwater resoiirce corresponds t o t h e average valiie of maximimi wi t t i d r a m l s under a steady reginie of flow, i . e . when t h e n a t u r a l groundwater d e p o s i t i s decreased (develcpment o v e r d r a f t ) , thus enabling t h e imxiniuun recharge from s u r f a c e

and

r a i n w a t e r , a l s o by a n a r t i f i c i a l recharge, :is well a s from o t h e r a q i i i f e r s . The t e c h n i c a l l y i i t i l i z a h l e y i e l d of water resmirces i s t h a t p o r t i o n of the t h e o r e t i c a l y i e l d (in 3 p e r v c a r ) which is defined by t h e p o s s i b i l i t i e s of repil a t i n g the flow regiiiie, by t h e p o s s i b i l i t i e s of l o c a t i n g r e s e r v o i r s , a s w e l l a s bv t h e rccharge and o v e r d r a f t p o s s i b i l i t i e s of t h e r e l e v a n t aqriifers e t c . The t e c h n i c a l l y u t i l i z a b l e y i e l d is l i m i t e d by topographical, hydrogeological and eiivironnieiitnl f a c t o r s , t h e p o s s i b i l i t i e s of c o n s t n i c t i i i g dams, r e s e r v o i r s and

216 TABLE 3 . 3 Classification

Form of interpretation

Aquifers (waterbearing f o m t i o n s )

Groundwater reservesvolume of water stored i n the aquifer, i . e . s t a t i s t i c a l l y expressed i n the same mnner as other mineral resources.

1) exploitable en mass 2 ) local and unimportant 3) u t i l i z a b l e for other purposes 4 ) unsuitable f o r any use Induced recharge

Basic characteris t i c s

Aquifer boundary Source of data

Quantity evaluation

Quality indicators

Protection measures Environmental impact and economy of opera tion

Measuring unit m3

Groundwater flow-groundwater resources expressed i n the same mnner as surface runoff.

1.s-I 3 -1 (m .s )

Water entering the aquifer from other aquifers and from the surface as 9 r e s u l t of water withdrawal.

1.s

-1

3 -1 (m .s 1

Categories according t o the cognizance of basic characteristics A B C explored under followed up investigation exactly under investi- k n m , not exactly determined gation l a i d down d r i l l i n g and archives observation network short-term pumping Pumping interplay with hydraulic and hydrologic.al hydromet eoromethods logical prognosis factors bf the basic information technology of future water treatdevelopment ment, pollution effect determined not y e t l a i d down proved by investigation determined i n optimum opera- not y e t l a i d down tion regime detail

Groundwater resources offered by a hydrogeological u n i t , i . e . by a geographically and physically limited sys tern of aquifers and aquicludes. Categories of groundwater according t o the adequacy of cognizance of basic data. st.ructures for a r t i f i c i a l recharge etc. It a l s o depends on the f l e x i b i l i t y of water mnagement i n the sphere of water users.

217 f i e economically u t i l i z a b l e y i e l d is a p o r t i o n of t h e t e c h n i c a l l y u t i l i z a b l e y i e l d and i s defined by t h e economic c r i t e r i a ( e . g . maximum c o s t p e r m3 of supplied w a t e r ) accepted by o r given t o water risers i n t h e r e l e v a n t stage of econorric development. The economic and s o c i a l development of h u m n s o c i e t y a f f e c t s and reduces t h e n a t u r a l and t h e o r e t i c a l y i e l d of water resoiirces , both q i i a l i t a t i v e l y i e . g . by p o l l u t i o n ) and q u a n t i t a t i v e l y ( e . p . by decreased recharge). On t h e o t h e r hand, t e c h n i c a l development r e s u l t s i n a n i n c r e a s e i n t h e t e c h n i c a l l y and economicallv u t i l i z a b l e y i e l d ‘e.F. through bigEer r e s e r v o i r s , o r an i n c r e a s e i n a c c e p t a b l e costs). Catchment boundaries (dividirip l i n e s

form t h e n a t u r a l geographical frame-

work f o r t h e compilation of water b a l a n c e s , u n l e s s t h e groundwater s t r a d d l e s the r e l e v a n t d i v i d i n g l i n e . The following natural yield

(2,

S

L

d~e f i n e s , without s t o r a g e f a c t o r s , the

f o r a s h o r t term p e r i o d , whose d u r a t i o n depends on natriral

r e t e n t i o n c a p a c i t i e s , and, with s t o r a g e f a c t o r s incliided, t h e t h e o r e t i c a l

SLIS-

tained y i e l d (2+, provided t h e r e l e v a n t period i s a long-tenn one:

(m3 )

(3.41

(3.5)

QS

- t o t a l s u r f a c e rlinoff

(m

3

-

Qs, - t o t a l s t o r a g e i n r e s e r v o i r s -1 (m3 .s 0

Gp - t o t a l grolindwater runoff -

G

gr

-

grolindwater r e s e r v e

- time

t

The precedinE

equation corresponds t o the n a t u r a l s t a t e of t h e catchment

without any anthropogenetic i n f l u e n c e s . But t h e h a r n e s s i n g of water resources can never b e considered independently of w a t e r withdrswals, water p o l l u t i o n and

I

o t h e r anthropogenetic a c t i v i t i e s whose i n f l u e n c e can be expressed a s follows:

-[

I dt -

14

F

/

+

Y dt

I4 d t +

/ / [ F dt +

- Yr

- water withdrawals -

L dt +

waste water d i s p o s a l - return flow

Ggdt

+

Gar

+

(3.6) (m3. s-l

1

(m3 .s-l )

/

G

. dt-

R1

21 8 L

-

C, .81

I

water conveyance from (+) and t o (-\ o t h e r catchments

(m3.s-’)

induced groundwater r e s e r v e s

(m3.

- decrease i n groundwater recharge, i f n o t recovered i n s u r f a c e resources

Y - i r r e v e r s i b l y pollilted portior. of

s-’

)

(m 3 . s -1 ) 11113. s-’ )

nrnoff

Yr - i r r e v e r s i b l y w l l i i t e d s t o r e d voliime

(m3

Tne determination of t h e s a f e y i e l d i s a l s o a problem of t h e adequacy of the copnizance o f resources (Tab. 3 . 3 ! , c a t e g o r i z a t i o n , i n v e s t i g a t i o n , measi!rability end a knowledpe of t h e i n t e r r e l a t i o n s h i p s of d i f f e r e n t c a t e g o r i e s o f water occurrence, e s p e c i a l l y of s u r f a c e water and groundwater. Water r e s o i ~ r c e scan generally be considered as (a’

conventional - i.e . t r a d i t i o n a l s m f a c e and groundwater resources which

a r e withdrawn, pimped, t r a n s p o r t e d , r e p i l a t e d by r e s e r v o i r s , d i s t r i b u t e d e t c . fbi

non-conventional

- geothermal resoiirces , c o l l e c t e d (harnessed) d e w f a l l ,

s c a - w a t e r , icebergs e t c . l!nder t h e second category i t is a l s o necessary t o consider t h e i n c r e a s e i n conventional rescurces by non-conventional

water u s e techniques such a s a r t i f i -

c i a l r a i n f a l l e t c . ( s e e paragraph 5 . 5 ) . For an assessment of lJSahle groundwater resources i t i s indispensable t o know the hydrodynamic parameters o f a l l t h e r e l e v a n t a q u i f e r s . The e x t e n t t o which these resources can be iised depends e s p e c i a l l y on t h e spacing between w e l l s

7r

g a l l e r i e s (ghanats e t c . ) . To reduce t h e n e g a t i v e environmental e f f e c t s , i t is necessary t o determine t h e most s u i t a b l e o p e r a t i n g c o n d i t i o n s such a s pimping r a t e s , draw-down l i m i t s e t c . The t h e o r e t i c a l y i e l d formula

R

of groundwater ret.oiirces can be expressed by t h e

(m

Groundwater can be d e l i b e r a t e l y overpumped

3

irl

(3.7)

t h e period of high water de-

mand i n t h e knowledge t h a t i t w i l l h e recharged n a t u r a l l y o r a r t i f i c i a l l y i n the period of abundant water supply. Such an o v e r d r a f t has t h e c h a r a c t e r of mining minerals and is l i m i t e d by t h e volime of t h e groundwater reserves and by the d u r a t i o n of t h e overpumping:

(m3 .s -1

13.8)

219 - overpumping gm tm - duration of overpumping ( o v e r d r a f t )

G

The d i f f e r e n c e between the t h e o r e t i c a l yield

f m3 .s -1)

(s)

? and the economically u t i l i z a b l e

0ge

This reserve c o n s i s t s m i n l y of lowforms t h e non-utilizable reserve (? FJ’ q u a l i t y groundwater resources and resoclrces of unstable o r low y i e l d . The eco-

/

nomicall =

ge

/

u t i l i z a b l e y i e l d i s thus Gg d t +

zgr +

G . dt -

Pl

go

(m3)

(3.10)

The equilibrium of input and output of water within a n a t u r a l geographical area (catchment) over a long period forms s u i t a b l e conditions f o r t h e environmental equilibrium, i . e . f o r t h e s t a b i l i t y of regional ecosystems. Such a balance of water resources and n a t u r a l needs can be expressed by t h e equation

+I

3

C dt

!m )

(3.11)

0

Q, , Gg - s u r f a c e and groundwater inflow

(m3 .s -1)

P

- precipitation

L

- water conveyance from (+) and t o (-) o t h e r catchments

Os, 0g - s u r f a c e and groundwater outflow E

- evaporation

C

- water consumption (of Q,, P, L)

G

8’

(m3. s-’ )

The majority of these data i s measured, s y s t e m t i c a l l y c o l l e c t e d and processed. Data concerning evaporation E and water consumption C a r e generally incomplete. Groundwater inflow and outflow cannot be measured d i r e c t l y and have t o be determined from t h e changes i n t h e groundwater reserve. Any inaccuracy i n t h e estimate of r e l e v a n t values should correspond t o t h e p o s s i b i l i t i e s of reg u l a t i n g the outflow.

220 The degree of environmental changes and damges depends not only on t h e d e r r e e of disturbance of t h i s balance, on i t s d u r a t i o n , and p e r i o d , but a l s o on the tolerance of t h e r e l e v a n t ecosystems t o changes i n r e l e v a n t components P ,

Q, and L g’ quality.

G

a s w e l l a s on an induced or hazardous d e t e r i o r a t i o n of water

3.3 BAIANCE OF WATER RESOURCES APD NEEDS The balance of water resources and needs compares t h e q u a l i t y and quantity of a v a i l a b l e water resources, i . e . t h e economically u t i l i z a b l e y i e l d , with t h e water requirements, s o t h a t t h e measures which a r e necessary t o s a t i s f y the demnds can be analysed. These balances evaluate t h e a c t u a l or planned u t i l i z a t i o n of water, i t s l o c a l i z a t i o n , course and n e c e s s i t y . Each balance of water resources and needs r e l a t e s t o a c e r t a i n geographical u n i t . The most s u i t a b l e u n i t s f o r t h i s purpose a r e catchments, which o f f e r a v a i l a b l e hydrological d a t a and t h e p o s s i b i l i t y of synthesizing s u r f a c e and groundwater d a t a , a s well a s p a r t i a l r e s u l t s from t h e various neighbouring catchments. From the hydrological point of view a q u i f e r s , r e s e r v o i r s or t h e i r systems a r e a l s o s u i t a b l e . P r a c t i c a l purposes r e q u i r e water balances t o be compiled for d i f f e r e n t a d m i n i s t r a t i v e a r e a s , towns, c o u n t i e s . b u t a l s o f o r l a r g e farms and industrial estates. When danarcating the boundaries of such a water management d i s t r i c t , the rel a t i o n s t o t h e neighbouring water management u n i t s have t o be considered i n o r d e r t o incorporate these data h i e r a r c h i c a l l y i n t o those of l a r g e r geographical units . The o p e r a t i o n a l management of water resources u t i l i z a t i o n r e q u i r e s (a)

a c u r r e n t evaluation of the a c t u a l state of t h e water balance,

(b) a p e r i o d i c (yearly) evaluation of t h e balance of t h e previous year. Apart from t h i s , medium-tern ( f i v e years’ and long-term (twenty t o f i f t y y e a r s ) balances should be determined f o r planning purposes, I n t h e framework of t h e planning and investment process long-term, medium term and short-term water needs a r i s e , i.e. q u a n t i t i e s of water intended f o r a p a r t i c u l a r use i n i n d u s t r y , a g r i c u l t u r e , i n f r a s t r u c t u r e or f o r the population.

These needs c a l l f o r planning or, i f short-term, f o r immediate a c t i o n . They should be revised a s they change and become water demnds a f t e r t h e i r o f f i c i a l approval and a f t e r t h e construction of t h e r e l e v a n t p r o j e c t . These water needs and water demands exceed t h e r e a l water requirements (Fig. 3.1). The water requirement r e p r e s e n t s t h a t p a r t of water denland which must be s u p p l i e d f o r t h e given technological process. An i n e v i t a b l e water requirement r e p r e s e n t s t h a t p a r t of t h e water requirement which niust be supplied by applying an optimal water-saving technological process. The water withdrawal and the

22 1

WATER N E E D S N ( quality quantity)

+

WAT E R WITHD RAWALS W (quality +quantity)

WAT E R DEMANDS A (quality quantity)

+

MANAGEMENT OF THE COURSE OF WATER OCCURRENCE AND USE;

WATER DELIVERIES

P R O T E C T I O N OF WATER RESOURCES AGAINST DETERIORATION AND EXHAUST0N;FLOOD CONTROL: PROTECTION AGAINST HARMFUL EFFECTS OF

&

WATER SUPPLY j WASTE WATER DISPOSAL

WATER REQUIREMENTS R (quality +quantity)

Fig. 3.1. Schematic r e p r e s e n t a t i o n of .,water needs, demands, withdrawals, d e l i veries and requirements i n the framework of the planning, investment and operat i o n process. water d e l i v e r y generally exceed water requiranents d i f f e r i n g

from the amount of

water paid f o r . The r e l a t i o n between t h e mentioned categories can be expressed i n t h i s way:

N

$

A

7> la 7> D 7> R > R;

$

$ QP

(3.12)

The r e l a t i o n between t h e water q u a l i t y i n d i c a t o r s i n these categories can be expressed i n a s i m i l a r way:

N~ " l . . . n - planned water needs and planned water q u a l i t y i n d i c a t o r s , A, 7'

a l . . .n- o f f i c i a l l y approved water demand and approved q u a l i t y i n d i c a t o r s , Wl...n

- water withdrawal, a m u n t of water d i v e r t e d from a stream o r a groundwater resource and i t s water q u a l i t y i n d i c a t o r s ,

delivery,amount of water supplied t o t h e water u s e r and releD, d l . . . n - water vant water q u a l i t y i n d i c a t o r s ,

R, rl*..rl

' 'il..

- water

requirement, t h e amount of water required by t h e water user under t h e given economic and production conditions,

. i n - indispensable water requirement, t h e amount of water which i s indispensable t o .ensure t h e technological process, by applying a l l known water-saving techniques,

222 IJ’

U’’‘’n

QP, qp!.

- w a t e r u s e , the amount of water r e a l l y used f o r the r e l e v a n t purpose and a c t u a l water q u a l i t y i n d i c a t o r s ,

. .n

- a m u n t of water paid f o r and corresponding water q u a l i t y indicators.

The econoniy of the water development process depends on the m u t u a l r e l a t i o n s between the above values. The necessary water supply can be determined from the (indispensable) water requirements with a reserve f o r l o s s e s e t c . , deducing the amounts supplied from in-plant resources such a s water reiise and re-cycling, storage e t c . A c e r t a i n r e s e r v e , marked by the s i g n

>

between water demnd, water with-

drawal, water supply and water requirements forms the conditions f o r a f u t u r e extension of the production. Idhen t h e s i g n < occurs between these values, operational troubles m y occur. With regard t o water q u a l i t y i n d i c a t o r s , a reserve is necessary i n each case f o r manifold and multipurpose water use, o r to t r e a t water f o r any of these d i f f e r e n t purposes. The problem with t h e present p r a c t i c a l compilation of the balance of water resources and needs m i n l y a r i s e from t h e i r inadequacy i n r e s p e c t of the following p o i n t s : ( a ) r e l e v a n t s u r f a c e and groundwater resources a r e not analyzed from the point of view of t h e i r economic f e a s i b i l i t y , but i n the hierarchy of t h e i r c o g nizance/present u t i l i z a t i o n , depending mainly on the i n e r t i a of the p a s t development and on the e x t e r n a l influences of o t h e r braches of the n a t i o n a l economy, (b) t h e motivation of relevant water needs i s not s u f f i c i e n t l y analysed, r e s i l t i n g i n the approval of t h e excessive water demands and i n an extensive

development of i n d u s t r i a l o r a g r i c u l t u r a l production on account of the water (and o v e r a l l ) development, financed generally from s t a t e f i n a n c i a l resources, ‘c) d i f f e r e n t methodological conditions of occurrence and s t a t i s t i c a l i n t e r p r e t a t i o n of t h e s u r f a c e mter and groundwater ( e . g . groundwater and surface water including r e - u s e of waste waters both from s u r f a c e water and groundwater a r e analysed s e p a r a t e l y . The overdevelopment of one of these resource categories m y be a consequence of o r the reason f o r t h i s p r a c t i c e ) . ‘d) non-conventional water resources a r e n o t taken i n t o account s u f f i c i e n t l y . The problem of t h e compilation of t h e balance of water resources and needs does not concern s u r f a c e and groundwater resources only, b u t a l s o s o i l water and r a i n f a l l . S o i l water safeguards the majority of p l a n t water requirements. I n a r i d and s e m i a r i d a r e a s , t h e problem of the m i n t e n a n c e of t h e vegetative canopy has to be included i n t h e r e l e v a n t water balance considerations. The water requirements of t h e v e g e t a t i v e canopy can be included i n t h e framework of the i r r i g a t i o n water requirements. S o i l water including t h e stock of the

capillary r i s i n g groundwater can a l s o be excluded a t t h e beginning of the compi-

223 l a t i o n p r o c es s , because t h e water which i s a v a i l a b l e f o r the e va potra nspira tion depends on local co n d i t i o n s , thus forming

2

closed system of l o c a l water supply

and production, and water balances a r e ge ne ra lly compiled f o r s u p e r i o r land complexes. The h e t e r o g en ei t y of t h e a v a i l a b l e d a t a , t h e diffe re nc e s i n the e x t e n t and frequency of measuring, and t h e d i f f e r e n t methods of data recording and statist i c a l e v a l uat i o n a l l tend t o complicate t h e common compilation of s u r f a c e and groundwater balances. The b a s i c inequation f o r t h e compilation of water balances and needs is / m3 . s-l , m3 )

Q

$

N

Q

- a v a i l a b l e water resources

N

- w a t e r needs (water withdrawals W)

(3.14)

3 -1 , m3 ) ( m3.s-l , m3 ) (m .s

This b a s i c inequation can be

formulated f o r both t h e surfa c e and groundwater resources of a c e r t a i n geographical u n i t f o r a lim ite d pe riod i n t h e following way Qs + Qsr + G

.s

+ G

gr

+ L +

F

5

W

+

bQ + G (m 3 pe r period) go

13.15)

Qs - s u r f a c e water inflow Qsr - s u r f a c e wat er i n reservoirs G - groundwater inflow g G - groundwater r es er v e

F

L

- water conveyance i n t o t h e area

F

- r e t u r n flow - waste water

I4

- water withdrawals i n cl u d i n g water conveyance from the a r e a

l Q - r e q u i r ed minimum d i s ch ar g e G

go

-

groundwater outflow

The b a l a n ce f o r s u r f a c e water is expressed as follows: Q, + Qsr

+

L - I + F = Ids + N)

(m3 p e r pe riod)

(3.16)

(m’ pe r pe riod)

(3.17)

and f o r groundwater resources

G +G g

gr

+I

=

W +G g

go

I - i n f i l t r a t i o n i n t o groundwater resources from s u r f a c e re sourc e s, waste water and water conveyance

224 W

- w a t e r requirements covered by s u r f a c e water resources

LJ

-

S

F:

water requiremets withdrawn from groundwater resources.

Class

Water q u a l i t y

Characteristic suitability

TJsage

I.

a . very clean

drinking water

b . clean slightly polluted

domestic uses l i v e s t o c k breeding

urban and r u r a l supply, food and p h a m c e u t i c a l i n d u s t r y , swimming pools l i v e s t o c k breeding, water s p o r t s and recreation

111.

intensively polluted

o t h e r uses

i n d u s t r i a l supply, irrigation

IV.

deteriorated

s e l e c t e d in-stream uses

n o t s u i t a b l e f o r withdrawal uses, only f o r n a v i g a t i o n , hydropower generation, waste disposal

11.

Categories of water q u a l i t y according t o i t s e f f i c i e n t usage ( s e e Tab. I . 2 4 ) . TABLE 3.5

Group

Characteristics

A.

Water acceptable f o r r e l e v a n t purposes of usage without treatment o r a f t e r simple pre-treatment

B.

Water acceptable f o r relevant purpose of usage a f t e r inexpensive, simple treatment

C.

Water acceptable f o r r e l e v a n t purpose of usage a f t e r s p e c i a l , but economical l y f eas i b 1e treatment

D.

Water acceptable f o r r e l e v a n t purposes of usage a f t e r an economic a l l v u n f e a s i b l e treatment

Groups of water q u a l i t y according t o t h e f e a s i b i l i t y of water treatment f o r t h e required purpose of usage. The purpose of the compilation f o r m t h e b a s i c d i f f e r e n c e between t h e hydrol o g i c a l balance and t h e balance of water resources and needs: The hydrological balance analyses t h e q u a n t i t y of water i n t h e hydrologic c y c l e , i . e . t h e inflow i n t o and t h e outflow from c e r t a i n geographical u n i t and simultaneously the increment o r decrement of water i n s i d e . The balance of water resources and needs analyses t h e q u a l i t y and q u a n t i t y of a v a i l a b l e water resources and t h e i r seasonal f l u c t u a t i o n , comparing them with t h e course o r development of t h e r e l e v a n t water needs (demands, with-

225 drawals, requirements) i n relevant categories of water q u a l i t y (Tab. 3 . 4 ) . I n addition to t h i s available water resources can f o r water development purposes be categorized according t o the f e a s i b i l i t y of water treatment for the required purpose of usage (Tab. 3 . 5 ) .

3.4

PIINIMUM WATER TABLE AND MINIElUM DISCHARGES

The functions of water a r e manifold and any u t i l i z a t i o n of water resources must not be allowed to hinder e i t h e r the natural functions of water o r i t s genera1 u t i l i z a t i o n by human society. It i s , therefore, of paramount importance to safeguard the s o c i a l functions of water and i t s e s s e n t i a l ecological functions, especially f o r

( a ? the conservation of the natural ecosystem i n the rived bed, (b) the conservation of the sediment transport, (c) the conservation of the hygienic and a e s t h e t i c functions of water, Id> the conservation of the natural vegetative canopy within the sphere of influence of groundwater withdrawals, ( e j conservation of the groundwater t a b l e and the natural ecosystems along water courses. The water regime has a b a s i c influence on the biological balance i n ecosystens. Changes i n the water regime occur a s changes i n flooding, the season of i t s occurrence, i t s duration and frequency, the

-

depth and velocity of flow i n the flooded area, the water and sediment q u a l i t y ,

-

i n the groundwater regime: i n the groundwater recharge, groundwater level

fluctuation and q u a l i t y , especially i f t h i s water supplies the s o i l moisture of the s u p e r f i c i a l layer. The occurrence of a minimum water table i n a r i v e r , and a minimum groundwater table along i t s course, depends on the occurrence of minimum discharges, provided t h a t the water t a b l e is not impounded a r t i f i c i a l l y . Therefore, during minimum discharges a c r i t i c i a l s i t u a t i o n occurs, whose long-term influence on the e x i s t i n g naturzl conditions determines the c q o s i tion of the relevant ecosystems. When the values of water discharges influenced by human a c t i v i t i e s such as reservoir operation o r water withdrawals exceed the yearly minimum, the balance of ecosystems m y not be disturbed, even i n the case of an increase i n the frequency of the occurrence of low discharges o r i n the case of an extension of t h e i r duration. In many cases, depending on the n a t u r a l conditions and adaptability of ecosystems, even a decrease i n n a t u r a l discharges below the value of t h e yearly minimum need not necessarily have a s i g n i f i c a n t l y harmful e f f e c t . Taking t h i s i n t o account, the value of t h e admissible minimum discharge can be derived from the minimum yearly discharges i n the following way:

226

Im3 . s -7 )

(3.78)

PQ

- minimum admissible discharge (minimum acceptable flow?

r

t h e n a t u r a l minimum y e a r l y discharge, usually 9 355d the r a t e of minimum discharge reduction ( r 5 1)

sin-

I n t h i s way the minimum acceptable flow can be derived frcm t h e minimum monitored discharees only (Tab. 3 . 6 ) . I n rmny cases such a n o v e r s i m p l i f i c a t i o n does not lead t o a p p r o p r i a t e res u l t s . The r a t e of minimum admissible discharge reduction i s a function of - climatic factors

*C

-

geomorphological f a c t o r s ‘m b i o l o g i c a l f a c t o r s ( a d a p t a b i l i t y , drought r e s i s t a n c e ) Xb - groundwater regime and s u r f a c e water regime

%d

- water q u a l i t y ( n a t u r a l p o l l u t i o n ) X 9 - anthropogenic f a c t o r s ( a r t i f i c i a l p o l l u t i o n , required water u t i l i z a t i o n

xx

etc.) I t goes without saying t h a t t h e minimum admissible discharge o f t e n depends

on t h e season and may, t h e r e f o r e ,

Xn=fm (Xc

Xm

>

m - month (1,2,3

xb

Xw

3

Xq

d i f f e r f o r each month Xx)

.

m Qmin (m3.S-l)

,....... 12)

(3.19)

ctm

Furthermore, t h e maximum admissible duration of t h e minimum discharges a l s o depends on t h e season and can be expressed a s a function of t h e degree of the discharge reduction tm= Fm (XC

, xm , xb , xw , xq , XX) “tn

!days?

(3.20)

Tnin

Vmin- n a t u r a l

minimum discharge i n t h e month m

The above f a c t o r s o r t h e r a t e of t h e minimum discharge reduction and its adm i s s i b l e d u r a t i o n h a s , t h e r e f o r e , t o be derived on the b a s i s of t h r e e groups o€ criteria : (1) c r i t e r i a of environmental p r o t e c t i o n , (2) criteria of in-stream water u t i l i z a t i o n ,

(3)

criteria of withdrawal p r i o r i t i e s .

The criteria of environmental p r o t e c t i o n include:

227 (a)

t h e c r i t e r i o n o f b i o l o g i c a l equilibrium i n t h e stream channel, i.e. corn

p l i c a t e d problems w i t h regard t o t h e undistrubed development of a q u a t i c l i f e , ‘b)

t h e c r i t e r i o n o f t h e e x t e r n a l e q u i l i b r i u m i n t h e landscape, i . e . con-

s e r v a t i o n o f n a t u r a l t e r r e s t r i a l ecosystems, ( c ) t h e c r i t e r i o n o f t h e physical e q u i l i b r i u m i . e . determination of minimum discharges which do n o t upset t h e balance of t h e erosion and sedimentation processes i n t h e r i v e r bed, Id)

t h e f i r s t c r i t e r i o n of w a t e r q u a l i t y , i . e . n o t allowing i t t o exceed t h e

mximum a d m i s s i b l e chemical, b i o l o g i c a l and h e a t p o l l u t i o n l e v e l s , i n o r d e r t o p r o t e c t groundwater resources ( e ) t h e f i r s t c r i t e r i o n of water t a b l e a l t i t u d e , required f o r a e s t h e t i c enj oymen t . The c r i t e r i a of in-stream water u t i l i z a t i o n i n c l u d e : (a)

t h e c r i t e r i o n of hydrolof.ica1 balance, i .e. deterinination of minimum

discharges which l i m i t e x c e s s i v e drainage of groundwater o r permit t h e i n e v i t able i n f i l t r a t i o n , (b’

t h e second c r i t e r i o n of t h e m t e r t a b l e , required f o r t h e general water

u t i l i z a t i o n i n t h e r i v e r channel, a s w e l l a s f o r navigation and r e c r e a t i o n . fc)

t h e f i r s t c r i t e r i o n of d i s c h a r g e s , necessary f o r power g e n e r a t i o c , t h e second c r i t e r i o n of water q u a l i t y , i . e . determination of the nece-

(d) ssary d i l u t i o n of waste waters t o safeguard t h e undisturbed course of n a t u r a l

s e l f - p r i r i f i c a t i o n processes and enable general water u t i l i z a t i o n , f i s h e r y . recreation e t c . , The c r i t e r i a of withdrawal p r i o r i t i e s i n c l u d e : la)

t h e second c r i t e r i o n of discharges t o cover r e l e v a n t downstream water

withdrawals, (b)

t h e t h i r d c r i t e r i o n o f water q u a l i t y , i . e . determination of t h e waste

water d i l u t i o n which would permit s a f e and economic water treatment processes f o r f u r t h e r water u t i l i z a t i o n by the p o l l u t i o n and i n d u s t r y . A l l these c r i t e r i a depend on l o c a l c o n d i t i o n s . Tne e s t a b l i s h e d values may d i f f e r , depending on t h e above f a c t o r s (Xc,. . . .Xx). The problem of minimum adm i s s i b l e discharge is g e n e r a l l y considered as a hygienic and economic one. I n such a way, t h e environmental f a c t o r s a r e n o t accordingly taken i n t o account. Tne a p p r o p r i a t e determination of t h e minimum admissible discharge is hampered by inadequate information, i n a d d i t i o n t o t h e economic o b s t a c l e s , l e g i s l a t i v e and i n s t i t u t i o n a l problems and t h e lack of r e s p o n s i b i l i t y of t h e a u t h o r i t i e s towards t h e needs of t h e s o c i e t y . Depending on t h e given economic p o s s i b i l Lties, t h e approved minimum admissib l e discharge can be used t o s e r v e environmental purposes, o r t o cover e s s e n t i a l withdrawals, i . ? . t o f u l f i l l only some or a l l t h e above-mentioned c r i t e r i a . Taking mainly economic f a c t o r s i n t o account, minimum admissible discharges a r e

228 determined on t h e b a s i s of a compromise between t h e c o s t of waste water t r e a t ment on t h e one hand and the economic l o s s e s which m y occur a s a r e s u l t of t h e d e t e r i o r a t i o n i n water q u a l i t y and t h e subsequent l i m i t a t i o n s of water supply t o lower r i p a r i a n users on the o t h e r hand. A p r a c t i c a l assessment of t h e minimum acceptable flow depends i n t e r a l i a on water requirements f o r e f f l u e n t d i l u t i o n t o achieve t h e requested water q u a l i t y , characterized e . g . by 8 mg of t h e b i o l o g i c a l oxygen demand BOD5 i n e f f l u e n t s , whose q u a l i t y depends on t h e admissible waste water p o l l u t i o n i n t h e a r e a i n question. Discharges w i t h i n t h e l i m i t s of Q355d

t o Q270dcan a l s o be assessed,

depending on the type and s t a t e of geological formations which do n o t destroy the groundwater regime andlor which safeguard the conservation of the charact e r i s t i c ecosystem e t c . !Tab 3.6). TABLE 3 . 6 \dater course

Minimun discharge

Mountain creeks

0.'

Water courses with a r e l a t i v e l y steady flow

0.5 0.8 - '1.0Omin

Other water courses

%in

Rin

Minimum acceptable discharges MQ according to t h e recomnendation t o the Economic Conmission f o r Europe of the United Nations (1970). When t h e minimum admissible discharge i s e s t a b l i s h e d , n o t respecting the c r i t e r i a of in-stream water u t i l i z a t i o n and t h e c r i t e r i a of withdrawal p r i o r i t i e s , p r a c t i c a l discharge l i m i t s should be determined f o r each stream s e c t o r t o safeguard a l l e s s e n t i a l requirements f o r in-stream water u t i l i z a t i o n and essent i a l water withdrawals. I n such a way a minimum value of n o t less than Q355d

can be accepted a s

l i m i t i n g j u s t below t h e d a m p r o f i l e . Corresponding t o t h i s i n a s e c t o r of a stream n o t influenced by t h e e f f e c t of a r e s e r v o i r the minimum admissible discharge may be assessed w i t h i n t h e l i m i t s (3.21) I n t h e intermediate s e c t o r s , t h e r e l e v a n t values decrease down t o the p r o f i l e , where the reservoir impact i s n o t apparent. I n any case, the minimum admissible discharge should a l s o depend on t h e water q u a l i t y , i.e. be higher f o r low water

I quality, e.g. Q355d i n s t e a d of I Q364d. An assessment of the minimum admissible discharge m y make i t necessary t o take measures t o change e x i s t i n g r e s e r v o i r operation and t o l i m i t water withdrawals so as t o r e s p e c t t h i s value e t c . A u t h o r i t i e s might approve of a drop

229 below these values i n exception c a s e s , b u t l i m i t it t o some lower values. Every appropriate measure should be taken t o safeguard the necessary minimum discharge including t h e construction of r e s e r v o i r s o r conjunctive use of groundwater and surface water discharges whenever t h e p o s s i b i l i t y of f u r t h e r water withdrawals occurs. ACTIVE AND PASSIVE WATER B A M C E

3.5

The equilibrium of water balances and needs s i g n i f i e s t h a t no a c t i o n has t o be taken t o s a t i s f y e x i s t i n g needs i f no f u r t h e r uses a r e planned. For such a s t a t e an i n t e r v a l of 2 10%has t o be introduced t o make allowances f o r the elast i c i t y of demand and i t s adaptation t o water shortages and a l s o f o r the unc e r t a i n t i e s of data c o l l e c t i o n and processing. Water demands can be c u t by up t o 20%without any important negative operational and economic consequences (Fig. 3.2). The minimum admissible discharge f o r environmental p r o t e c t i o n and in-stream water u t i l i z a t i o n (not including any withdrawals) has t o be regarded a s an indispensable water need. Bearing t h i s i n mind, t h e balance of water resources

and needs may be considered t o be i n equilirbium i f

(3.22)

i n each of t h e l o c a l i t i e s ( r i v e r s e c t o r s ) considered Wi - water withdrawals (W. <

Q

-

Q-

PQ)

d a i l y dischargesfgroundwater y i e l d

(daily

- rn3

p e r day)

(m3 p e r day)

Fi - o u t l e t discharge ( r e t u r n flow) FQ - minimum admissible discharge

!Q

- MQ)

- usable water resources

(m3 p e r day) 3 (m p e r day)

This balance is t h e r e f o r e favourable ( a c t i v e ) i f

f f Wi-

i=l

Fi ( 0 . 9 Q - P Q

(3.23)

i=l

and unfavourable (passive) i f

f f Wi -

i-1

Fi> 1.1 Q

- PQ

(3.24)

i=1

A favourable balance of water resources and needs i n d i c a t e s t h a t a b s t r a c t i o n

f o r e x i s t i n g water uses can be extended and new uses can be s a t i s f i e d , including water conveyance i n t o neighbouring a r e a s with passive balances. The unfa-

230 Water d e l i v e r y

Average decrement

Losses of water u s e r s

Measures

No economic

Un im p o r t o , ti only short- t e r m 'decrease

Nil

losses

Medium decrease o r long p e r i o d o f low

of decrease

Substantial but short-term decrease *

Substantial and long term limitation or c u t t i n g the delivery

-

Losses do not excees the expenses for emergency water supply

-

for development of new resources

Losses exceed the development expenses for additional resources

Genera I l i m i t a t ion of d e l i v e r y

Emergency delivery, general substantial limifations

Development of additional resources, their mutual interconnection

*

Fig. 3.2. Consequences of a decrease i n water d e l i v e r y and necessary operational o r investment measures (p - r a t e of guarantee, R - water reqtiirements). vourable 'passive) water balance i n d i c a t e s t h e need f o r a development of new water resources o r f o r water conveyance from neighboilring catchments with an a c t i v e water balance. From t h e operational point of view i t i n d i c a t e s the need f o r r e s t r i c t i n g present water uses and f o r c u t t i n g down e x i s t i n g water uses e . g . by excluding i n e f f i c i e n t uses and through the introduction of water-saving techniques. 'when compiling

balances of water resources and needs, the balancing e f f e c t of

o u t l e t discharges should be taken i n t o account F

=

C

- water consumption

Id-C

("3 \,

(3.25)

(m3)

The compilation of s t a t i s t i c s of the i n t e r r e l a t i o n s h i p s between water supply (amour.t of water siipplied) and water conslimption gives a b a s i c p i c t u r e of deve-

23 1 lopment p o s s i b i l i t i e s by t h e a p p l i c a t i o n of water re-use and recycling techniques i n the sphere of water u s e r s , Nevertheless, i t does n o t mirror the possibi-

l i t i e s of o t h e r water-saving techniques which a r e t o be considered s e p a r a t e l y , i n connection with r e l e v a n t technological processes (Tab. 3.7). TABLE 3.7 ~

Balance of water resources and needs

Basic equation

c)

Favourabl e (active) In equilibrium Ilnfavourab l e (passive)

>

1.1 I\r

Q

< 0.9 ld

>

~~~

Measures

9

New water uses can be developed

0.1 Q

1x1 < 0.1 x

~

Coefficient of usage of water resources

/do.

x>O X

Q 5 1 .lId

0.9W

Water surplus or deficit

0.9&p& 3.1

Q

NO a c t i o n necessary

Water .us: restriction, water r e s o u r ces development

( 0

1x1 > 0.1

p1.1

Q

~~~~~

Q u a n t i t a t i v e indices of t h e balance of water resources and needs. I n p r a c t i c e , t h e d i f f e r e n c e between usable water resources and demnds i s o f t e n used a s an important q u a n t i t a t i v e i n d i c a t o r . It i s c a l l e d water s u r p l u s i f p o s i t i v e , o r water d e f i c i t i f negative, and is t o be derived from s t a t i s t i c a l records i n t h e following m n n e r

X

Q-W+F

x

=

X

- water

i.e. (,,3 , m 3. s -1

Q-c surplus f + ) , water d e f i c i t (-)

(3.26)

(m3 , m3 .s -1 )

On t h i s b a s i s , t h e r a t e of usage of a water resource i s t o be defined by the

ratio

f W; i=l

0

n

t F;

i=1

(3.27)

(3.28) expresses t h e degree o f water re-use of r e l e v a n t resources. The reversed value of t h i s r a t i o , applied t o the whole country and covering an average year, was introduced by Balcerski (1968) for comparing water resources u t i l i z a t i o n i n different countries:

232

(3.29)

cm- index of water management k

Qi - mean annual surface and groundwater (m3 per year)

J=1

f i=1

runoff of the whole country IJi - annual water needs of the whole

(m3 per year)

country

This index of water management does not express the a c t i v i t y or passivity of water balances and needs. It characterises the r a t i o of surface and groundwater resources development and u t i l i z a t i o n - a t the beginning of economic development and - the re-use of water a t further stages of development. This index does not include the internal recycling, i . e . the repeated use of the same water inside a closed c i r c u i t of different water users. It characterizes the development of water management i n the relevant country/area and the coordination of the repeated use of the same water by the different users, but does not characterize the efficiency of water use by relevant water users. Quantitative indices of water u t i l i z a t i o n depend on the season, especially i f i r r i g a t i o n requirements prevail. This unevenness can be expressed by the r a t i o of a summer r (April to September) and wlnter rw (October t o March) w i t h drawals o r by the r a t i o of summer cs and winter water consumption cw: n ws; ww; iwa; r = i=l r = i=1 1=1 (3.30)

f

S

W

f

i=l wai

f f wa;

1

i=I

i=l

(3.31)

c S

IJai - annual water withdrawals Idsi,

Idwi - water withdrawals i n the summer

3 !m ? (m3)

and winter season

3

Fai - return flows

(m per year)

Fsi,Fwi- return flows i n the sumer and winter season

rm'

per season)

23.3 PROBABILITY OF THE SATISFACTION OF WATER REQUIREPEN'S

3.6

The course of water a v a i l a b i l i t i e s Q and of water consumption C can be ex-

pressed as a function of t i m e

(3.32)

Their d i f f e r e n c e water s u r p l u s o r d e f i c i t X i s , t h e r e f o r e , a l s o a function of time

X

=

Q - C

=

fl (t) - f2 (t)

=

f

(3.33)

3 (t)

The p o i n t s of i n t e r s e c t i o n of t h e time function of a v a i l a b l e water resources and the time function of t h e i r consTmption d i v i d e the period of the a c t i v e and passive water balance. The d u r a t i o n of the p a s s i v e balance, i . e . of nonguaranteed water supply, depends n o t only on t h e q u a n t i t a t i v e v a r i a t i o n of water resources i n time, b u t a l s o on the course of water withdrawals and consumption, i . e . on the s t r u c t u r e of water u s e r s . S i m i l a r s t r u c t u r e s of water users under the same c l i m a t i c conditions produce similar time functions of water consumption. RATE OF GUARANTEE FOR DIFFERENT DELIVERY REGIMES

FLUCTUATION OF WATER DELIVERIES (REQUIREMENTS) AND WATER AVAIL ABI L IT IE S

equi-

equilibriurn for DI

equilibriurn for D2

.....- ...... ........- ............. .............. passive balance ective balance for DI

b

%

t

rate of guarontee

for DI

Fig. 3 . 3 . Chronological r e p r e s e n t a t i o n of the course of water d e l i v e r i e s . (requirements), water resources a v a i l a b i l i t y and the d u r a t i o n curve of r e l e v a n t water balance states: DL-3 - water d e l i v e r i e s (requirements), 3 average values, Q - a v a i l a b l e wa er r e s o u r c e s , t - time.

234 Fluctuation i n water consumption can therefore be characterized by average values and by the r a t e of t h e non-guaranteed water supply evaluated i n the same rranner as t h e course of discharges i n hydrology: by the duration curve. Such a duration curve i n d i c a t e s t h e duration of the non-guaranteed water supply (%) i n the given long-term period f o r the relevant course of the water consumption, characterized by t h e average value (Fig. 3.3). The decrease i n water requirements increases t h e r a t e of guarantee and extends t h e duration of t h e favoura b l e balance of water resources aiid needs [requirements). P r a c t i c a l l y , the i n t e r v a l

2

10% f o r t h e equilibrium of water balances and

needs has t o be considered and r e l e v a n t curves derived from values correspondi n g t o t h e increased values of water a v a i l a b i l i t y by 10%and average values of

water consumption ( o r f o r c h a r a c t e r i s t i c water resources data and water consump t i o n ) decreased by 10%. The r a t e of guarantee of t h e water supply has t o be economically considered from t h e p o i n t of view of - t h e water u s e r , - the w a t e r supply o r g a n i s a t i o n , - t h e n a t i o n a l economy. The c o s t of water f o r i t s u s e r can be expressed a s t h e function M = f(W) M

W

(3.34)

- c o s t p e r u n i t o f production ($ p e r t ) - amount of water suppljed t o t h e (per u n i t of product m p e r t , m .etc. water withdrawal W, d e l i v e r y D , or water demand A, depending on methods of payment and nasurement)

yter

A g r i c u l t u r e and industry can operate without r e s t r i c t i o n o r i n t e r r u p t i o n s ,

i . e . a t f u l l capacity, when D => R i =< R Ri - t h e minimum discharge with which the user is a b l e t o operate without l i m i t i n g t h e production f indispensable water requirement) ( 2 . s - l , m

D - water d e l i v e r y R

-

(D

< W)

t h e discharge which meets t h e user's requirenents without using watersaving techniques

.t-1 )

f r n3 .s -1)

(m3 .s -1 )

A l i m i t a t i o n o r i n t e r r u p t i o n of t h e water supply causes economic losses i n industry and a g r i c u l t u r e . A decrease i n t h e water supply beneath the lower l i m i t R . r e s u l t s i n a n inmediate, non-proportional increase i n c o s t s p e r u n i t of production '%I. The production r a t e decreases , a l s o o f t e n influencing the

235 q u a l i t y of production, both i n a g r i c u l t u r e and i n industry. A f u r t h e r decrease i n water supply can r e s u l t i n a similar non-proportional inc re a se i n c o s t s

Of3>, because production can be ensured e . g . by a n emergency w a te r supply only, and i n a g r i c u l t u r e by c u t t i n g down t h e a r e a under i r r i g z t i o n . I t is q u i t e obvious t h a t a decrease i n water supply below a c e r t a i n l i m i t i n g value de finit e l y i n t e r r u p t s t h e production p r o ces s , b u t a minimum discharge Rmin may s t i l l be r e q u i r e d f o r t h e maintenance of some processes i n industry and f o r conserv a t i o n a l purposes i n a g r i c u l t u r e !Fig. 3 . 4 ) .

3 m nax

PRODUCTION R~GIME c

c

Fig. 3 . 4 . Graphical r ep r es en t at i o n of t h e influe nc e of l i m i t i n g water d e l i v e r i e s on o p er at i n g c o s t : Rmin - i n d i s p e nsa ble water requirements (e .g. with - water requirements w ith no re c yc ling, Ro t rmximum r e c y c l i n g ) , ,R, optimum discharge t o be a b s t r a c t e d fronrr! t h e u s e r s viewpoints, M 1 - operating c o s t s under d i f f e r e n t production and water de live ry regimes, )&,in - minimum c o s t f o r t h e u s er .

4

The guarantee rate of water requirements s a t i s f a c t i o n is simply t h e proba b i l i t y of s a t i s f y i n g t h e q u a n t i t a t i v e conditions of water requirements L

P

= L1 t . 100%

p

- t h e guarantee rate of water requirements s a t i s f a c t i o n

(3.36)

tl - t h e d u rat i o n of t h e s a t i s f a c t i o n of water requirements (days) t

- t h e analysed long-term period

(days)

236 By optimizing water use i n a g r i c u l t u r e and i n d u s t r y , a n optimum discharge can be determined, thus safeguarding the required production a t minimum c o s t f o r t h e u s e r , 5 . e . optimum discharge t o be a b s t r a c t e d from the u s e r ' s viewpoint, o r f o r the n a t i o n a l economy, i . e . from the s u p e r i o r nation-wide p o i n t of view ( R . ) . m e o v e r a l l e f f i c i e n c y of the water supply does n o t depend on the water c o s t borne by t h e water u s e r , b u t on the r e l e v a n t c o s t of t h e water resources development and operation and on t h e losses r e s u l t i n g from t h e c u t t i n g down of production borne by t h e n a t i o n a l economy. But t h e economic r e l a t i o n s between the water iisers and organisations respons i b l e f o r the water supply a r e one-way. Relevant economic and l e g a l feedback is not s u f f i c i e n t t o p r o j e c t accordingly t h e l o s s e s t o t h e water s u p p l i e r : These organisations a r e only a f f e c t e d by t h e decrease i n income from r e s t r i c t e d water siipply o r by t h e p o s s i b l e duty t o safeguard a compensatory emergency water supply. A decision on t h e r a t e o f guarantee has t o be taken from t h e over-all p o i n t of view of t h e n a t i o n a l economy: Supplementary water resources development, generally borne by the national economy, i s economically f e a s i b l e i f the t o t a l losses cause by the i n t e r r u p t i o n o r the decrease i n the water supply exceed t h e t o t a l construction and operation c o s t s . TAB11 3 . 8

Water u s e r

Rate of guarantee (%)

Population:

Water u s e r

Rate of guarantee (%)

Power production :

Big c i t i e s

95

I n t e r s t a t e sys tem

99

Small c e n t r e s

so

Local system

90

Agriculture:

Industry :

F i e l d crops

75

Intensive cultivation

85

Interstate importance

97

Local importance ~

Water t r a n s p o r t :

Int e r m tiona 1 National Local importance

Recreation

90

~~~

80

95 85 60

The recomiended guarantee rate of water requirements s a t i s f a c t i o n f o r b a s i c categories of water u s e r s . The f u l l s a t i s f a c t i o n (100%) of water requirenients f o r t h e n a t i o n a l economy is completely uneconomic, r e q u i r i n g a disproportionate developnent of water resources, i n c e r t a i n cases a l s o emergency r e s e r v o i r s and networlts. It is very

237 important t h a t an increase i n the guarantee r a t e of a few per cent within the l i m i t s from 80 t o 95, and especially from 95 t o 99 per cent r e s u l t s i n a disproportionate increase, i n a doubling o r even i n a higher increase of construction and operation c o s t s . I t is therefore indispensable to accept t h a t the water supply could be decreased and even interrupted during periods of a lack of water o r during necessary maintenance and reconstruction works. The l i m i t s of t h i s guarantee r a t e depend on the relevant economic and s o c i a l losses (Tab.

3.8). The r a t e of guarantee does not only depend on q u a n t i t a t i v e , but a l s o on q u a l i t a t i v e parameters. The conditions f o r s a t i s f y i n g the quality requirenients With the necessary degree of probability a r e of two types; i . e . for quality indicators, which must (a)

2

q;

-

be g r e a t e r than the necessary concentration (oxygen content e t c . )

q;,

(3.37)

not be g r e a t e r than the allowable concentration

(b)

(3.38)

(i= 1,2..., n-l,n

thermal, chemical, biological and bacteriological pollution).

The r a t e of guarantee f o r q u a l i t a t i v e conditions represents the probability of exceeding the necessary and not exceeding the admissible indicators. The guarantee r a t e of water requirements s a t i s f a c t i o n i s therefore a function of many randcm variables f(R)

=-

probability

(Q

2

R

,

' I '

To determine t h i s probability with the necessary accuracy requires daily records of q u a n t i t a t i v e data concerning water resources and water requirements. The density of water q u a l i t y data need not be even, but must embrace any occurrence of pollution which exceeds the accepted l i m i t s . The guarantee r a t e of water requirements s a t i s f a c t i o n m y be p r a c t i c a l l y expressed i n three ways: ( a ) guarantee of duration (b)

guarantee of volume

(c)

guarantee of frequency

X

t

xV

xf The guarantee of frequency, expressed by the r a t i o of the number of years (or days) with a c t i v e balance o r balance i n equilibrium and the t o t a l nunber of years of the given period, defines n e i t h e r the r e a l frequency of the interruption of the water supply, nor the depth of the water deficiency, nor i t s r e a l

238 duration. The economic e f f e c t i s q u i t e d i f f e r e n t i f these days a r e spread o r accumulated. The r a t e expressed by the r a t i o of the number of years, though used q u i t e o f t e n , is almost without p r a c t i c a l use (Tab. 3.9). TABTX 3.9 Rate of guarantee

Formula

Guarantee of duration

x

t

t' = --

t

Guarantee of volume

%=F

Guarantee of frequency

Xf

=

Y' y-

Remarks

t - t o t a l duration of the period t ' - accumulated duration of the periods i n which the use i s s a t i s f i e d

w

- t o t a l volume of water requirements W ' - volume of water a c t u a l l y supplied Y - t o t a l number of years i n the period Y ' - number of years i n which the water use is completely s a t i s f i e d

Rate of guarantee f o r q u a l i t a t i v e water requirements expressed a s a percentage o r f r a c t i o n of the whole according t o the Economic Commission f o r Europe (1973). The guarantee of duration and of volume have the same disadvantage, namely t h a t of expressing neither the frequency nor the duration of the relevant disturbances of supply. The r e l a t i o n between the three mentioned r a t e s i s : Xf

<

Xt

"V

(3.40)

The r a t e of @larantee of volume may exceed 1 (one), exceeding the guarantee of duration i n a l l cases. The guarantee of frequency, expressed by numbers of years, represents the smallest value, i l l o g i c a l l y accepting the t o t a l annual period as passive, i f only a few days occur with a passive water balance. To characterize the guarantee r a t e of water requirements s a t i s f a c t i o n by mostly appropriate figures, i t i s necessary to determine the c h a r a c t e r i s t i c s i n t e r r e l a t i o n s between the three indicators mentioned i n the following way : - t o find the year With the highest number of days with a passive water balance, - t o s e l e c t the longest period of the passive balance within t h i s year,

-

t o determine the guarantee of volume during t h i s period,

-

t o check whether a lower value of guarantee does n o t occur i n sane other

period. The appropriate value of the guarantee r a t e of water requirements s a t i s f a c tion is expressed by the figure selected i n t h i s way.

239 FLOW CONTROL AND OPERATING SCHEDULES

3.7

The d e s i r e d d a i l y equilibrium o r a c t i v e balance of water requirements and water a v a i l a b i l i t i e s has t o be achieved by flow and groundwater a b s t r a c t i o n cont r o l . Schedules and guides f o r both s u r f a c e and groundwater withdrawal and the regulation of flow and r e s e r v o i r operation should be developed i n advance i n order t o determine the most e f f e c t i v e methods of water u t i l i z a t i o n . Operating procedures form a complex of fixed and conditioned r u l e s , whose aim

i t is t o influence the l o c a t i o n and t h e t i m e d i s t r i b u t i o n of water occurrence and i t s q u a l i t y . These o p e r a t i n g procedures include r u l e s f o r s u r f a c e and groundwater withdrawal, t h e s t o r a g e of excess water i n r e s e r v o i r s and a q u i f e r s ,

its i n f i l t r a t i o n , pumping and conveyance, t h e r e l e a s e of s t o r e d water, the cont r o l of i t s q u a l i t y by the control of the r e t u r n flow and i t s b e n e f i c i a l use f o r t h e sake of the s o c i e t y . Surface water bodies d i f f e r frcm underground water bodies by t h e i r flood detention e f f e c t . River beds, r e s e r v o i r s , polders and r i v e r valleys o f f e r storage f o r the immediate accumulation of water discharges, prism s t o r a g e and, during the advance of a flood wave, a l s o wedge s t o r a g e . The degree of flood control o f f e r e d by t h e r e s e r v o i r depends on t h e r a t i o of the flood volume t o the detention s t o r a g e o f f e r e d a t the moment of any harmful overtopping of the n a t u r a l and a r t i f i c i a l banks i n a given reach of stream. The degree of flood control can be characterized by t h e frequency of the flood volume occurrence, when the s t o r a g e

F

=

V

I 'Qf

0

(3.41)

- Qo, dt

- s t o r a g e volume of the r e s e r v o i r

Q, - flood discharges

(m3 ) (m

3 s-l

maxinum discharge, n o t causing harmfal I'm overtopping of r i v e r banks

Qo

-

t

- time (duration of the flood)

3 .s-l )

.

)

A l m o s t a l l modern r e s e r v o i r s a r e m u l t i p u r p s e . The e f f e c t i v e storage capacity of such a r e s e r v o i r can be t h e o r e t i c a l l y divided i n t o t h e flood-control

storage

and the s t o r a g e capacity reserved f o r b e n e f i c i a l use. I t i s e s s e n t i a l t h a t the r e s e r v o i r capacity reserved f o r the s t o r a g e of flood water should be emptied a s soon a s p r a c t i c a b l e a f t e r a flood. I n s u f f i c i e n t flood-storage capacity m y re-

sult i n a concentration of maximum discharge from t r i b u t a r i e s , thus increasing the maximum flood discharge i n s t e a d of decreasing i t . The storage f i l l e d up bef o r e the a r r i v a l of the peak flood reduces the d u r a t i o n , b u t n o t the extent of imunda t i o n .

240 To optimize t h e operating procedures f o r t h e multipurpose u t i l i z a t i o n of res e r v o i r s , the modifying e f f e c t s on discharges including floods passing through a r e s e r v o i r , polder e t c . have t o be determined by routing on the b a s i s of (a\] c o l l e c t e d chronological sequences of hydrological data and data on crater use, chronological sequences of s y n t h e t i c hydrological d a t a and water needs, general p r o b a b i l i s t i c data on water requirements and water a v a i l a b i l i -

(b) (c) ties,

(d) frequency a n a l y s i s of t h e s t o r a g e volume a t the boundary of t h e time intervals. Operating schedules, r u l e s and guides depend on t h e lay-out and technical equipment of r e l e v a n t p r o j e c t s and systems. Depending on t h e r e l e v a n t lay-out and equipment, t h e function of water development p r o j e c t s and systems is (a)

c o n t r o l l a b l e and thus c o n t r o l l e d o r uncontrolled, u n c o n t r o l l a b l e , i . e . r i g i d and not dependent on t h e decisions of the

(b) o p e r a t i n g personnel.

Consequently, t h e o p e r a t i n g r u l e s a r e e i t h e r r i g i d o r f l e x i b l e . Rigid schedules depend mostly on ungated s t r u c t u r e s o r on unconditional binding operat i o n s . The day-to-day

operation i s o f t e n based on semi-rigid schedules, on

conditional rules dependent on t h e flow and the water requirements, on t h e i r c u r r e n t and forecasted s t a t e . Tne decision can be determined beforehand and expressed i n t h e form of graphs and t a b u l a t i o n , f o m l a t e d by t h e operating c e n t r e o r done on s i t e by r e l e v a n t decision-makers o r by the operating person n e l , a s t h i s should be l a i d down beforehand on t h e b a s i s of t h e t h e o r e t i c a l s t u d i e s o r of previous experiences. To increase t h e flood control e f f e c t of

a r e s e r v o i r , the a c t i v e storage

capacity reserved f o r b e n e f i c i a l use m y be p a r t i a l l y emptied, depending on t h e flow f o r e c a s t . Such a r e l e a s e and b e n e f i c i a l use of water is a l s o useful f o r l i m i t i n g t h e expected b u t n o t b e n e f i c i a l l y usable s p i l l ( f o r power generation), which m y occur e s p e c i a l l y when the r e s e r v o i r is f u l l before the beginning of t h e new cycle of r e s e r v o i r operation. Under such circumstances, the release of water i s economically f e a s i b l e i f the economic e f f e c t from the b e n e f i c i a l u t i l i z a t i o n of such water balances the r i s k of l o s s e s which m y occur i n t h e next period of r e s e r v o i r operation (Fig.

3.5;. According t o Hugh-Blair Smith !1960), t h i s condition may be formulated as follows :

O,,+-

a d d i t i o n a l r e l e a s e of water during the month Ic

(m3)

241

s-k - forecasted inflow i n t h e remaining (m-k) month period of t h e operation

(m3)

cyc 1e

V - t o t a l active storage

\i - volume a v a i l a b l e om+

(rn 3 )

i n the r e s e r v o i r i n the month k

- outflow from t h e r e s e r v o i r according (m3 ) t o t h e b a s i c operation

Idhen On+

< 0,

the a d d i t i o n a l r e l e a s e of water = 0. An a d d i t i o n a l l i m i t a t i o n f o r

water p a r e r generation is

(3.43)

-

unused capacity of t h e power p l a n t according t o the b a s i c operation

Q

MONTHS

Fig. 3.5. Supplementary outflow from a r e s e r v o i r on t h e b a s i s of a medium-tern inflow f o r e c a s t increases the e f f i c i e n c y of water u t i l i z a t i o n i n comparison with a r i g i d operating schedule, based on a c t u a l water a v a i l a b i l i t i e s . 1 - supplementary outflow, 2 - water s u rplus (nonavailable o p e r a t i v e l y ) , 3 - water surplus a v a i l a b l e . o p e r a t i v e l y , 4 - unused capacity of the system (reserve f o r seasonal i n c r e a s e i n requirements). The a d d i t i o n a l r e l e a s e of water is not economically f e a s i b l e i f t h e economic e f f e c t from t h e f i l l e d r e s e r v o i r exceeds t h e economic e f f e c t from t h e b e n e f i c i a l u t i l i z a t i o n of water damstream. The economization of r e s e r v o i r u t i l i z a t i o n can a l s o be achieved by the reduct i o n of withdrawals t o safeguard water i n s t o r a g e f o r l a t e r use. The f e a s i b i l i t y of such a decision has t o be proved on t h e b a s i s of t h e b e n e f i t s a r i s i n g from t h e decreased r i s k of a water lack i n t h e next period. The e f f i c i e n c y of such operation can be proved when t h e function of t h e economic l o s s e s i s n o t l i n e a r . Under such circumstances, t h e lowering of water withdrawals i n t h e period pre-

242 ceding t h e period of t h e expected water deficiency i s motivated by the higher b e n e f i t s t o accrue from t h e same amount of water. Such a reduction of water withdrawals i s j u s t i f i e d i n the period of reduced useful s t o r a g e (Fig. 3.6) and is u s e f u l i n the course of a short-term period, because hydrological and meteorological f o r e c a s t s f o r longer periods a r e not sufficiently reliable.

3 -I m. s

-rrrrrr

WATER DELIVERY

PREVIOUS REDUCTION IN DELIVERIES

MONTHS LACK OF WATER

Fig. 3.6. The decrease i n economic l o s s e s from water deficiency by reducing water d e l i v e r i e s before t h e period of unfavourable balances of water resoiirces needs: a . o r i g i n a l values without previous reduction i n water d e l i v e r i e s , b . reduced values of water d e l i v e r i e s before the period of the forecasted drought, r e s u l t i n g i n a rediiction i n the lack of water i n the period of water deficiency. W a t e r d e l i v e r i e s marked black, deficiency hatched). For the optimum u t i l i z a t i o n of the mximim volume of water i n water r e s e r v o i r systems i t is necessary t o d i s t r i b u t e t h e r e l e a s e of water among the relevant r e s e r v o i r s , s o t h a t t h e empty p a r t of t h e useful storages i s i n r e l a t i o n to the inflow expected on the b a s i s of a statistical and p r o b a b i l i t y a n a l y s i s i n the remaining period before the beginning of t h e next operation cycle. Shoemaker (1960

9

expressed t h i s p r i n c i p l e inlathematically on the b a s i s of the

q u a l i t y of the r a t i o of the empty s t o r a g e of one r e s e r v o i r to the empty s t o r a ges o f a l l t h e r e s e r v o i r s , and t h e r a t i o of t h e expected inflow of one reservoir to t h e expected inflow of a l l the r e s e r v o i r s i n the system as follows:

243

(3.44)

n.

- number

m

- number of months i n the operation cycle

of reservoirs

Vj - useful storage of the reservuir j

v.'Ic - the volume of water

3 (m

Q. - the inflow of water i n t o reservoir j during the month k

(m3)

i n the storage of reservoir j i n the month 1c

-

3

outflow from the reservoir j during j k the m n t h k

(m )

Or - controlled increase of runoff i n the

fm j

0

r e s t of the period Qjcm-,c) - the expected inflow i n t o the reservoir j i n t h e - r e s t of the cycle of the reservoir operation

3

(m3)

Supposing t h a t Qr

=

0j k

=

(vjk

+

Qjk),

(3.45)

the release from reservoir j during the month k i s

The benefits from operation on the basis of t h i s principle a r i s e i n practice only i f the hydrological forecast is s u f f i c i e n t l y r e l i a b l e , i. e . mainly during spring discharges caused by the melting of snow. The formulation of a similar analog for water power generation requires programing, because relevant dams o f f e r difEerent heads , resulting i n the differences i n the benefits to a r i s e from a u t i l i z a t i o n of the same amount of water by the power stations of d i f f e r e n t dams. For the e f f i c i e n t use of the useful storage capacity i t i s indispensable (a, to release water e i t h e r f o r beneficial uses o r t o increase the floodcontrol storage i n the period of the expected surplus of water, to decrease the extent of floods o r the amount of water not beneficially used, (b) to decrease water withdrawals i n the period before the water deficiency, carefully balancing the r e s t r i c t e d benefits against the decrease i n expected

244 losses, ( c ? to manage the operation of a l l reservoirs which a r e capable of controlling and increasing the discharges i n the relevant water management profile i n such a way as to balance their empty storage against the inflow expected i n the next period, (d’ to increase the yield by a conjunctive use of surface and groundwater resources, to meet most needs i n normal and wet years by surface storage, to retain groundwater f o r use during years of low surface runoff and a l s o recharge t h i s a r t i f i c i a l l y i n periods of excess surface flow. In r e a l i t y , reservoirs and water resources systems are mnaged on the basis of incomplete knowledge. Operational decisions a r e taken on the basis of what the future s t a t e is expected to be, rather than of what it is known t o be. The optimal control of the outflow depends (a)

on the a b i l i t y to forecast future flow sequences,

(b) on the in€luence of the intermediate catchment: the prism and wedge storage of the river bed, inflows from unmeasured t r i b u t a r i e s , gains and losses due t o groundwater drainage, losses and evaporation, water withdrawals e t c . (c)

on the useful storage available a t the r i g h t moment,

(d)

on the control of the reservoir sluices.

MONITORING OF

FORECAST O F

THE ACTUAL STATE

THE FUTURE STATE

DETERMINATION O F

0 P E R AT10 N THE OPERATION PROCESS

Fig. 3.7. Schemtic representation of a cycle f o r tuning-the reservoir operation on the basis of results achieved by single steps of operation. Success i n managing a multi-purpose reservoir or a reservoir system i n real tine depends on a minimal delay between the measured change of s t a t e and the implementation of the appropriate control decision implemented (Fig. 3.7).

This delay depends above a l l on the equipment and the state of (a! the signalling system (hydrological and meteorological) (b) the decision making system (programing, simulation or brain-trust only),

245 ' c ; the operation system (communication, press-button reniote, centralized remote-control e t c . )

control on s i t e or

The degree of water losses a r i s i n g from current control i n comparison with the data of computerized centralized remote-control often exceeds 20%. The ext e n t and technical standard of the s i g n a l l i n g , decisionmalting and operation sys tem safeguarding the r e a l f l e x i b i l i t y of opemtion schedules should be determined by analyzing the relevant purchase and operation costs. The sum of these costs should exceed neither the increase of the induced benefits, nor the inves tment and opera tion costs of the emergency water supply.

3.8

SYSTENS I N WATER RESOURCES FIANAGDIENT

The framework i n which water management a c t i v i t i e s e x i s t forms a complex of r i v e r network systems, groundwater s t r a t a systems, water supply systems, irrigation systems, drainage and water disposal systems, flood control systems, water transport systems, water power generation systems e t c . , but a l s o the a b i o t i c , b i o l o g i c a l , l e g a l , economic, administrative, informational and other system of the environment (Fig. 3.5). This complex can be characterized by and subdivided i n t o /a)

the natural systems of catchments and aquifers,

Ib)

technical systems of i n l e t works, wells and g a l l e r i e s , reservoirs,

canal and pipeline networks e t c . with relevant signalling and control systems, ( c ) water supply, d i s t r i b u t i o n and disposal systems of water u s e r s , s i t u a t e d e i t h e r inside or outside water resources systems, {d) economic and administrative systems of water management, n a t u r a l , technical and socio-economic systems of the environment.

'e)

A system i s a s e t of elements whose i n t e r r e l a t i o n s h i p i s f a r more important

than t h e i r r e l a t i o n s t o the elements of the other systems which form i t s environment. The s e t of elements and l i n k s forms the s t r u c t u r e of a system (Fig.

3.9'. Important links i n water resources systems can be distinguished a s - material (hydraulic and hydrological - Fig. 3.11) - energetical (enabling the operation) - i m t e r i a l (economic, l e g a l , informational e t c . )

.

(n-I) n elements of a system can be connected mutually by not more than n links of the same type. An open system has a t least one l i n k with the environment. A closed system has no links With the environment and can be characterized by the Cartesian product S

=

{X?lcR}

x

=

{ x1 x2 .... .... xn}

R

=

{Rl

R2

(3.47)

.... .... Rn}

xi

- s e t s of elements xi

Ri - s e t s of elements ri

246

/ r , e Rl,

r2e R2, ...

. . . ,rnf

Rn)

H y d r o g r a p h i c o I ( w a t e r management\systems HYDROSPHERE CONTIENTAL WATER S Y S T E M INTERBASIN S Y S T E M

a R I V E R BASIN SYSTEM WATER RESOURCES S Y S T E M WATERWORK S Y S T E M

E n v i ronmental s y s t e m s

Socio- economic systems

Fig. 3.8. Hierarchy o f b a s i c systems.for water supply i n r e l a t i o n t o the n a t u r a l and s o c i a l systems which form t h e environment of the water supply and disposal sys tern . To achieve the optimum s a t i s f a c t i o n of the defined o b j e c t i v e s of water re-

sources s y s t e m , t o f i n d t h e i r most economic lay-out and function and t o achieve t h e i r harmony with t h e i r environment, water resources systems and t h e i r function sholild be optimized a t t h r e e d i f f e r e n t s t a g e s of t h e i r development: l a ) a t the. planning s t a g e - t o i d e n t i f y t h e optimum s t r u c t u r e of t h e system which s a t i s f i e s the needs w i t h i n t h e c o n s t r a i n t s imposed, i . e . t o a l l o c a t e resources so t h a t r e l e v a n t preconceived goals a r e a t t a i n e d as f a r a s p o s s i b l e , ( b ) a t t h e design s t a g e - t o optimize the s i z e of the components mainly on

the b a s i s of t h e topographic and hydrological data, e.g. t o select t h e l e a s t c o s t s o l u t i o n imposing minimum c o n s t r a i n t s on t h e f u t u r e development, or the s o l u t i o n of c r e a t i n g an i n t e g r a l component of t h e f i n a l development s t a g e , ( c ) a t the operational s t a g e - t o mnage a system i n such a way t h a t t h e a c t u a l needs a r e s a t i s f i e d up t o t h e design sr;ar?dard and the economic l o s s e s

(sometimes a l s o operational c o s t s ’ a r e minimized and the maximum b e n e f i t s achieved.

247

Mi

Fig. 3 -9. Schematic representation of hydraulic i n t e r r e l a t i o n s of one element i n a water resources system: a ) with the water users who form the eiivironment of the system, b \ With the water users incorporated i n t o the system. Q - water resources, R - water withdrawals, F - e f f l u e n t .

3.9

ANALYSIS &ID MIDELLING OF Iv'ATFX RESOURCES SYSTEMS Desirable functions of water resources systems can be achieved i n balanced

i n t e r r e l a t i o n s i n t h e i r subsys terns only, simultaneously f u l f i l l i n g d i f f e r e n t functions i n other systems, especially i n the technical and economic ones and i n the administrative system of water resources mnagement. To achieve these desired goals in an optimum way, h e u r i s t i c methods have t o be used. These methods, r e s t r i c t i n g the extent of searching and helping to formulate the solution, include s c i e n t i f i c appraisals i n the f i r s t extreme and exact algorithms i n the second. I n t h i s s p e c i f i c case it is unlikely t h a t any algorithm, a prescription f o r a s e r i e s of calculations t o be performed one a f t e r another, o r any s i m i l a r a n a l y t i c a l technique, would be capable of leading from the entry data t o the optimum solution. A hiera-chical approach i s needed, enabling many a l t e r n a t i v e solutions to be considered without a t t e n t i o n t o d e t a i l , i n order t o examine the best of them i n d e t a i l during subsequent stages. The complex problems of water resources require the use of d i f f e r e n t research and investigation methods (Tab. 3.10) and

248

.

various o t h e r techniques such a s p r o b a b i l i t y theory, modelling and mathemtical programming, operation research/systems a n a l y s i s e t c . TABZE 3.10

Sethod of research and i n v e s t i g a t i o n I

I

1

Studies and measurements i n prototype, v i g i l , benchmark b a s i n s , c a l i b r a t e d and paired catchments, u n i t source a r e a s and o t h e r e erimental p l o t s

Compilation and e x t r a p o l a t i o n of e x i s t i n g i n f o m a t i o n (graphical, single- and m u 1 t i v a r i a b l e analysis) I

!KIDEL STI'DIES: Model is a s i m p l i f i e d r e p r e s e n t a t i o n of t h e physical process;

only f e a t u r e s which a r e n o t e s s e n t i a l t o the study a r e omitted. Runoff and s t o r a g e

+ + +

+

Channel Reservoir Groundwater Land IIJater use

+ + +

+

+

I Physical model b u i l t to s u i t a b l e s c a l e t o r e w e s e n t the followl e d k p process s a t i s -

Water q u a l i t y

I

I

I

Clogging, waterlogging, erosion, sedimentation

+

+

+ + +

1

MODEL

MATHEMTICAL HODEL

A"1,E

Solution of mathemat i c a l equations reDres en t i n 2 the 'followed-:IT, process. I

Model of a s i m i l a r process from d i f f e r e n t physical phenomena which is e a s i e r t o follow up. ANALOGUE COblP1TEK

.4EORITFiN and t r a d i t i o n a l a r i thmetical c a l c u l a t i o n s .

D I G I T U L CObIF'LTER

I

HYBRID SOLUTION

s o l v i n g equations by means of electronic circuits

I

Research methods and m d e l s i n water resources management. Relevant methods a r e a p p r o p r i a t e t o d i f f e r e n t circumstances: Simulation methods use mathematical systems analogous t o t h e physical s y s t e m under study, which m y be manipulated t o produce o u t p u t data s i m i l a r t o observed d a t a . The v a r i a b l e s of i n t e r e s t i n t h e former correspond t o physical v a r i a b l e s . Mathemat i c a l p r o g r a m i n g is a technique f o r finding t h e optimun way t o accomplish t h e given purpose.

249

Fig. 3.10. Basic inputs and outputs i n systems of water resources and users: P - p r e c i p i t a t i o n , J - energy, Q - r u n o f f , a - water q u a l i t y i n d i c a t o r s , E evaporation, W P - water p u r i f i c a t i o n p l a n t , MflP - waste water treatment p l a n t . 1 - n a t u r a l systems, 2 - water resources systems: a ) channel and r e s e r v o i r network, b) w e l l s y s t e m , 3 - d i s t r i b u t i o n and waste water disposal systems of water u s e r s . The l i n e a r programing method i s a systematic procedure f o r t r y i n g various combinations of elements i n such a way t h a t t h e c o n t r o l v a r i a b l e comes nearer to each goal a t each try, always keeping w i t h i n t h e e s t a b l i s h e d l i m i t when a l l the r e l a t i o n s h i p s a r e l i n e a r . I n t e g e r p r o g r a m i n g i s used when t h e q u a n t i t i e s involved a r e l i m i t e d t o i n t e g e r v a l u e s . Dynamic programing i s the a p p l i c a t i o n of t h e theory of multi-stage decision processes. It leads t o an optimal policy by s t e p s , i n ways t h a t o f t e n correspond t o methods by decisions a r e made. Models a f f o r d a deep understanding o f the behaviour of the r e a l system, providing the p o s s i b i l i t y of introducing the necessary changes i n t h e s t r u c t u r e and operation of t h e system t o produce higher b e n e f i t s , decrease t h e relevant costs and reduce t h e r e l e v a n t negative e f f e c t s . Tne model of a water resources system i s a combknation of r i v e r s , c a n a l s ,

250

A

reservoirs aquifers diversion dams

-

______

rivers and streams signalling

---

Retwerk Cantrol network

a :%:' 0

+

water users Pumps

*gauging station rain-golge artificial infiltration

Y I

Fig. 3. 11. Schematic representation of a system of surface and groundwater resources . The monitoring and control systems a r e depicted for two water resources and one of the water users only. and pipelines, pumping, water purification and water treatment plants, hydropower s t a t i o n s (and t h e i r d e s i m heads) etc. Utilization variables concern the water supply f o r population and industry, areas under i r r i g a t i o n , power production e t c . and a r e mainly expressed i n cubic meters, kilowatt hours e t c . per year. Constraints r e l a t e mainly to the volume of water available i n reservoirs a t the beginning of the operation season or a t the beginning of each month, as well as to minimum f l m , the monthly demand of energy e t c . and to the nonnegat i v i t y of flow. The i t e r a t i v e computations with d i f f e r e n t combinations of components and different operating schedules make it possible to s e l e c t the optimum solution. Ihe capacity of computers as w e l l as practical reasons of the natural regulation of flow i n reservoirs and channels make it possible t o use ten daily or monthly averages as entry data for the analysis of the water supply, power generation

251

Fig. 3.12. Schematic r e p r e s e n t a t i o n of a s u r f a c e and groiindwater system f o r i r r i g a t i o n supply a t t h e confluence of two r i v e r s .

outputs y ( t

InDuts x ( t )

I Decision :

solution found.

I .nopt

Fig. 3.13. Flow c h a r t diagram f o r the s e l e c t i o n of t h e optimum combination of p r o j e c t parameters according t o P l a t e (1975).

252 etc. The b r e a k u p d a t a f o r f l o o d p r o t e c t i o n purposes should be i n more d e t a i l , a t l e a s t f o r s i x hour i n t e r v a l s , depending on t h e s i z e of t h e c a t c h e r i t and t h e course of floods (Fig. 3.13’. An i n c r e a s e i n t h e r e l i a b i l i t y of the r e s u l t s of optimization can be achieved by: (a\

a systematic s e l e c t i o n ar.d construction of a l t e r n a t i v e s , not by t r i a l

and e r r o r , ‘b) formulating and programing operating schedules i n such a way a s to form t h e v a r i a b l e p a r t of t h e model, o r s e l e c t i n g t h e optimum operating schedule on the b a s i s of a s y s t e m approach, (d generating a long-term series of s y n t h e t i c hydrological d a t a ( e . g . f o r f i v e hundred years ) , o r probable c h a r a c t e r i s t i c hydrological s i t u a t i o n s which d i d not occur i n the series observed, improving i n t h i s way t h e r e l i a b i l i t y of these e n t r y data f o r f u t u r e s i t u a t i o n s , e s p e c i a l l y i n periods of mininm and maximum r u n o f f , (d) e v a l u a t i n g t h e b e n e f i t s of r e l e v a n t water resources s y s t e m on t h e b a s i s of data whose s t a b i l i t y and r e l i a b i l i t y o r progressive i n c r e a s e o r dec r e a s e can a l s o be s p e c i f i e d p r e c i s e l y enough ir, periods t o come. These relia b l e d a t a have to be derived from t h e population growth and development of l i v i n g s t a n d a r d s , based on t h e optimum needs of one i n d i v i d u a l , -

( e ) employing a s e n s i t i v i t y a v a l y s i s , whose goal i t is to d e f i n e t h e d i s p e r s i o n i n t e r v a l of t h e entry d a t a , safeguarding t h e genera-

t i o n of the output d a t a i n t h e sphere of t h e optimum s o l u t i o n , - t o i d e n t i f y t h e group of c r i t e r i a which has the mst important influence on the s e l e c t i o n of t h e optimum s o l u t i o n and t o analyse t h e i r i n t e r r e l a t i o n s h i p , - t o maximize the functional s t a b i l i t y of the system by optimizing i t s s t r u c t u r e , l i n k s an’d management. Benefits and l o s s e s a r i s i n g from t h e operation of d i f f e r e n t water resources systems can be c h a r a c t e r i z e d by t h e s e t of a f f e c t e d hydrological data, by a s e t of geographical and economic d a t a , or by f i n a n c i a l i n d i c a t o r s . Benefits and l o s s e s , a s well a s t h e pay-off, are functions of t h e parameters of t h e system (Fig. 3 . 1 4 ) . Bi BI X1

=

Fi

(X1

5.......X n )

, B2 , . . . .,Bn - b e n e f i t s

3 , ....,Xn

(3.48) and l o s s e s

- parameters of t h e system

On t h e b a s i s of t h e d e c i s i o n c r i t e r i a f o r any combination of t h e entry data

and elements of t h e analyzed system a s e t of outcomes may be determined, each outcome with a determined degree o f p r o b a b i l i t y .

253

2 4 3

0

occurrence

Fig. 3.14. S i m p l i f i e d flowchart diagram f o r modelling o f a system o f multipurpose r e s e r v o i r s : A - number of i n v e s t i g a t e d conibinations a , B - number of i n v e s t i q a t e d o p e r a t i n g schediiles b , C - number of a i a l y s e d y e a r s n . System a n a l v s i s i s a r a t i o n a l approach e n t a i l i n g any o f t h e folloilring s t e p s (Fig. 3.15): ( a ) Analysing t h e problem a r e a , i d e n t i f y i n g i t s boundary and b a s i c i n t e r connections t o o t h e r problems, (b) Simplifying t h e problems tc t h e p o i n t of a n a l y t i c a l t r a c t a b i l i t v , pres e r v i n g a l l i n p o r t a n t a s p e c t s a f f e c t e d by varioiis p o s s i b l e s o l u t i o n s , defining the system, (c)

Defining t h e h i e r a r c h y of o b j e c t i v e s and g o a l s ,

(d)

I d e n t i f y i n g c r i t e r i a f o r decision-making, employing feedback mechanism,

254

2 Start

GOAL FORMULATION

, 1 SYSTEM DEFINITION

I

r I CRITERIA IDENTIFICATION .~ I

( \

I

I I

Yes

Can g o a l s b e c h a n g e d

Goals implemented? W es

Selection

bI

No

of t h e solution

OPTIMIZATION

I Selectior I

1

I

SENSITIVITY ANALYSIS

I

I -Chanaes I I I

\

~

IM odeis \ Goals i m p l e m e n t e d ?

w

,

L__r;l Changes accepted

1

Fig. 3.15. Flowchart diagram f o r the s e l e c t i o n and cptimization o f water resources sys tems

.

( e ) Modelling the system, examining appropriate a1 t e r n a t i v e s , i n o r d e r to optimize t h e s t r u c t u r e of t h e system, ( f ) Optimizing t h e function of t h e system, not omitting any dynamic interr e l a t i o n s h i p s a m n g t h e various components, (g) I n v e s t i g a t i n g the s e n s i t i v i t y of the r e s u l t s t o t h e assumptions made, including the i n c l u s i o n o r exclusion of t h e problem components, (h) Verifying t h a t t h e s e l e c t e d s o l u t i o n s a t i s f i e s t h e defined objectives and goals. The hierarchy of decision c r i t e r i a f o r development goals mainly includes ( a ) p o l i t i c a l c r i t e r i a , such a s f u l l employment, higher income and i t s b e t t e r d i s t r i b u t i o n , increased standards of l i f e , p r o m t i o n of i n d u s t r i a l / a g r i -

255 cultural development, e l e c t r i f i c a t i o n e t c . , (b) water management c r i t e r i a , e.g. - the increase of the r a t e of guarantee of water delivery for different categories of water users, - the increase of the r a t e of guarantee of flood protection, - economic u t i l i z a t i o n of resources available, (c) economic c r i t e r i a , e.g. fixed target a t l e a s t cost, benefit maximization, cost-benefit optimization. (d) environmental c r i t e r i a etc. The identification o f these c r i t e r i a determkes the relevant p o l i t i c a l , water mnagement, economic, envirmmental and other consequences : e.g. the minimization of relevant costs, expressed and realized a s the minimization of present costs to achieve the requested goals, forms obstacles to future development trends. Systems analysis with adequate entry data i s to be used for solving problems of multipurpose projects and i n conditions with a lack of data to identify problems. The possibility of a successful optimization is threatened by (a) tives,

not including the really optimum solution among the selected alterna-

not identifying the r e a l l y optimum function of the system, ( c ) the possibility t h a t the hydrological data a r e not sufficiently representative f o r the given task, (b)

(d) the low r e l i a b i l i t y of the economic data for the future period of the functioning of the system, (e)

unexpected environmental consequences, especially those with a substan-

t i a l economic impact. The mst common errors leading t o the f a i l u r e of systems analysis include - selecting the wrong models, - neglecting important components, links and feedbacks - constructing mdels which a r e too detailed and exhaustive, making i t d i f f i c u l t to s e l e c t the optimum solution, - using the process too rigidly o r using the wrong c r i t e r i a , i . e . those which do not lead to the requested decision, - analysing relationships i n the selected solutions which w i l l be altered i n the r e a l situation o r i f a problem solution is obvious. 3.10 ECONOMIC OPTMZATION AND FINANCIAL ANALYSIS Economic evaluationloptimization i s a method of selecting the o p t i m s o h tion for a useful u t i l i z a t i o n of limited resources such as capital, labour, land, water and other natural resources f o r different uses i n the interests of h m n society. It consists i n the selection of such a combination of structural

256 variables as t o minimize losses and maxi-mize benefits. I t s replacement by a minimization of investment costs i s not adequate. Investment costs should be used as one of the c r i t e r i o n furctions (Tab. 3.11). TABLE 3.11 Economic evaluation

Financial analysis

Goal

Growth of national income Better income distribution

Financ emen t bfoney p r o f i t

Objective

Select the project, enabling maxirnuni efficiency i n using c a p i t a l and natural resources available

Assessment of financial viabil i t y of economically o p t i n m pro j ec t

Viewpoint

(National) economy

Capital available t o the project-undertaking e n t i t y

Input

1.

Costs and benefits t o the economy 1.1 d i r e c t l y to the projectundertaking e n t i t y 1.2 affecting other e n t i t i e s and individuals 2 . secondary effects (transfer payments, sunk costs and i n f l a t i o n excluded)

Expenditures and revenues to the e n t i t y , external and secondary e f f e c t s excluded. Transfer payments, taxes, custom duties, subsidies and depreciation, interes t and amortization, sunk costs and general i n f l a t i o n excluded.

Prices

Shadow prices used, i f market prices do not r e f l e c t the true values of projects e f f e c t s N e t present worth “pw): Discounted costs and benefits, subtracted former from the latter.

Market prices used.

Result

EConomic r a t e of return (ERR): The discount r a t e equalizing the present worth of benefits and costs.

Estirfation of t o t a l c a p i t a l requirements, s p l i t up i n t o - local currency, - foreign exchange. Income statement, statement of financial sources, cash flow, balance sheet. Financial r a t e of return (FTX). Fimncial ratios : - return of fixed i s s e t s , - debt-service coverage by internal cash generation, - debt/equity r a t i o .

Characteristics of economic waluation/optimization and financial analysis Financial analysis is a method of assessing whether o r not the relevant entity o r e n t i t i e s intending t o undertake the project is capable of financing its construction and operation. The investment costs of a multipurpose project financed by several participants a r e generally expected t o be l e s s than the total of the costs of the single-purpose project t h a t would produce equivalent outputs. I n multipurpose projects there a r e

257 (a: separable costs which can be c l e a r l y separated and allocated to one of the participants S1' s2.....sn ib) common costs which a r e a l s o to be shared equitably by these p a r t i e s

ol,

02....o

The t o t a l cost of a multipurpose project i s , therefore T

=

f

(Sk -+ Oki

-t-

I

(3.49)

k=1

I

- irrecoverable subsidies.

TABLE 3 .12 Activities

Input o r output

I d e n t i f i c a t i o n 1. Direct costs and of benefits benefits - of the projectand costs undertaking e n t i ties, - of other e n t i t i e s and persons 2 . Transfer payments !taxes, subsidies and custom d u t i e s , i n t e r e s t and amortization, - i n f l a t i o n and deprecia tion excluded 3. Secondary e f f e c t s

Methods and tools

Other e f f e c t s and criteria

Comparison of s i t ~ t i o nw i t h and without p r o j e c t (no s t a t u s quo since even without the project development is l i k e l y )

Secondary e f f e c t s stemming f r m - project inputs f diiring cons truction) - project outputs ( a f t e r completion) expressed - e x p l i c i t l y by mu1 t i p l i c a t o r s applied t o p r i c e s , - implicitly by using shadow prices

Measurement of benefits and costs

Shadow prices based on opportunity cost principle OCC ( i f mrked prices a r e d i s t o r t e d ) - efficiency shadow prices - t o achieve income growth and i t s improved d i s t r i b u t i o n between consumption and investment, - s o c i a l shadow prices - t o distinguish between costs and benefits accrued t o poor and r i c h to achieve improved income d i s t r i b u t i o n

Comparison of benefits and costs

C r i t e r i o n of economic v i a b i l i t y : = difference between Absolute merit present worth of (single pro'ect) . benefits and t h a t of m d a t OCC ? = 0, costs using disERR -2 OCC counting technique. Relative merit (several proj ec ts ) Economic rate of M ax NEW a t OCC return (ERR) m$ o low t a r i f f = discount r a t e a t leading to waste which NPW = 0 High NPW - impedes Discount r a t e = economic growth opportunity c o s t of c a p i t a l (OCC) defined by Authoritv. Net present worth ("ld)

s e n s i t i v i t y analysis to deal with uncertainties affecting input data. Risk .analysis using probability d i s tributions for i m p o r tant projects. Qualitative .assessment of intangible aspects.

I d e n t i f i c a t i o n : measurement and comparison of benefits and costs.

258 There a r e a number of cost sharing methods, b u t the practical cost sharing is a r e s u l t of negotiations. Participants i n multipurpose projects a r e prepared to pay t h e i r separable costs and t h e i r share of c m n costs provided that t h e i r sum does not exceed the cost J (S,

+ ,0

< Jm) and prwided

ni

of an equivalent single-purpose project

t h e i r benefits exceed o r equal the costs

(3.50)

In mny countr:.es t a r i f f s a r e not well related t o costs of production and inves tmeiit i s often subsidized. IJnder such circumstances the expected n e t benef i t s of the relevant uridertalting cannot therefore be used as a scale for sharing the c o m n costs. The participants should, therefore, share the comon costs i n proportion t o t h e i r saving, r e s u l t i n g from the j o i n t project, i . e . i n proportion t o the equivalent single-purpose costs l e s s t h e i r separable costs i n the multipurpose project.. The range within which it i s reasonable t o negotiate the share of c o m n costs i s therefore

(3.51) k=l

J, , J2.. . .,Jn

-

costs of eqCiva1ent single-purpose projects

Costs and benefits must r e f l e c t the true value of project inputs, outputs and other e f f e c t s on the economy as a whole. Idher: the t a r i f f s do not r e f e r to the actual costs of resources used o r saved by consumer decisions, they a r e based on sunk costs and the backward-looking pricing approach of calculating accounting costs i s used. Price system d i s t o r t i o n s , namely - price control imposed by the government, - under- and overvalued currencies, - protectionist measures by import quota and customs duties, -

taxes and subsidies hidden i n prices,

-

mnopoly o r government control over c e r t a i n markets, i n t e r e s t r a t e s distorted by i n f l a t i o n e t c .

my lead t o the f a i l u r e of the law of supply and demand to operate freely. The valuation of resources requires a forward-looking pricing approach for calcul a t i n g future margiml costs, reconciling the t a r i f f and cost structure /Tab.

3.121.

259

,s PUNNING PIODELS BASED ON PHYSICAL PARAMETFR 3.11 Physical parameters can a l r e a d y be adopted a s a c r i t e r i o n i n the planning s t a g e . A simple planning model i n which s u r f a c e water and groundwater i n t e r a c t i o n s a r e e x p l i c i t l y included i n t h e p r o j e c t screening and sequencing process d i v e r s i o n s , r e s e r v o i r s , well f i e l d s , water c o n s i s t s of a set of run-of-river treatment p l a n t s and water conveyance p r o j e c t s (Fig. 3.16). The area may be divided i n t o N planning d i s t r i c t s . Water balances a r e t o be analyzed i n T years.

i I

II

I

i

i I

I

i

i

F i g . 3.16. Schematic r e p r e s e n t a t i o n of t h e m-th region i n t h e planning model according t o Maddock and Moody (1973); completed: ‘ Q - withdrawal of uncontrolled discharges, 2Q - withdrawal of c o n t r o l l e d dis-

water, 8Q losses, U

-

-

5

Q

- water

7

re-use, 6Q, ’ Q - conveyed waste water, water groundwater inflow, 9Q - t r e a t e d water, “Q water u s e r s , E - evaporation, P - p r e c i p i t a t i o n .

charges, 3Q - groundwater withdrawal, 4Q,

The planning process can be modelled by a mixed-integer programe whose objective functions minimize - t h e volume and d i s t a n c e of water conveyed,

-

t h e volume and l i f t of water pumped ( o r maximize t h e head and volume used

f o r power generation).

260 ' h e f i r s t o b j e c t i v e function may be w r i t t e n

I

N

tmin

c

-

(3.55)

category of t h e resource

a,Ac - index and total nur
t,T - index and t o t a l number of planning p e r i o d s m,n, N - i n d i c e s and t o t a l number of planning d i s t r i c t s (Ictma - volume of water supplied by p r o j e c t c d u r i n g t h e p e r i o d t from r e s c u r c e a

ip

district

dmac - d i s t a n c e of water conveyance by p r o j e c t c from t h e resource a i n d i s trict m

Qctman

- volume of water conveysd from (+) t h e resource a d i s t r i c t n t o dist r i c t m by p r o j e c t c during t h e period t

The second o b j e c t i v e f u n c t i o n d i f f e r s only i n t h e v a r i a b l e s T r e p r e s e n t i n g head

Adopting the minimum c o s t a s a c r i t e r i o n , t h e o b j e c t i v e function minimizes t h e p r e s e n t value of t h e c a p i t a l c o s t s and o p e r a t i n g c o s t s over the planning period. According t o Moody and Ehddock (1972) t h e o b j e c t i v e f u n c t i o n m y be adopted

2 [t

n-I

t=l

a=l

N

c=1

5

Qctma

*

Octma

+

5

hJ

Ictma

*

Kctm

+

Fn=Q1 c t m a n .

1 (3.57)

Octm

- o p e r a t i n g , maintenance and replacement c o s t s p e r u n i t of water supplied by p r o j e c t number a of t h e resource c i n planning d i s t r i c t m p e r planni n g period t d i t t o from planning d i s t r i c t n

Octmn-

Icm

-

t h e p r e s e n t v a l u e of c o n s t r u c t i o n c o s t s of p r o j e c t number a of t h e resource c i n planning d i s t r i c t rn

Imn - d i t t o i n planning d i s t r i c t n Kcm

-

i n t e g e r column v a r i a b l e - i f K = 1 , t h e c o n s t r u c t i o n of p r o j e c t numbera of t h e resource c i n planning d i s t r i c t m is completed a t t h e beginning of t h e planning p e r i o d t . Otherwise, K = 0.

261 This o b j e c t i v e function is s u b j e c t t o t h e following c o n s t r a i n t s : (a\

T o t a l water demand c o n s t r a i n t s : Total volume of water supplied and t h e

imports minus t h e exports must be g r e a t e r o r equal t o t h e t o t a l water demands i n planning region m during t h e planning p e r i o d t .

a=

Dm PQat

7

N

c=6

n=m

-

watcr needs i n planning d i s t r i c t m during the period t

-

volume of t h e minimum runoff of t h e resource c during t h e period t

fb)

P r o j e c t i n i t i a t i o n c o n s t r a i n t : No water may be supplied f r a n p r o j e c t a

of t h e resource c i n planning region m u n t i l t h e p r o j e c t has been completed. Once c o n s t r u c t e d , i t cannot provide more w a t e r than i t s y i e l d . ( c ) Processing c o n s t r a i n t s : The volume of t r e a t e d water produced by w e l l f i e l d s and water treatment p l a n t s and t h e volume o f t r e a t e d water imports must be g r e a t e r or equal t o t h e t r e a t e d water denlands. (d)

Flow requirement c o n s t r a i n t : The s i m of unregulated upland stream flows

i n planning d i s t r i c t m which d i s c h a r g e t o a stream segment r s , minus t h e withdrawals by d i v e r s i o n s and r e s e r v o i r s upstream of t h i s segment and t h e volume of water l o s t from t h e stream t o t h e underlying a q u i f e r due t o groundwater pumping, must be g r e a t e r o r equal t o t h e r e q u i r e d flows downstream of t h e segment rs. The values i n t h e flow requirement c o n s t r a i n t imply c e r t a i n seasonal p a t t e r n s of s u r f a c e water flows and downstream flow requirements, i . e . a set of o p e r a t i n g r u l e s which may be used t o a l t e r t h e timing of s u r f a c e water withdrawals due t o groundwater punping.

262 Chapter 4

IMPACT OF DEVEMPMENT A C T I V I T I E S ON THE HYDROIDGIC CYCLE

4.1

CfIANGES I N THE HYDROLOGICAL DATA

The long-term geomorphological development has formed s t a b l e , but s e a s o n a l l y v a r i a b l e conditions f o r t h e l i f e of t y p i c a l ecosystems i n d i f f e r e n t p a r t s of the n a t u r a l environment. A family of these s t a b i l i z e d , l o c a l ecosystems forms t h e r e g i o n a l ecosystem, which i s c h a r a c t e r i s t i c f o r t h e r e l e v a n t landscape and c l i matological c o n d i t i o n s . Inputs t o and o u t p u t s from t h e ecosystem a r e moved by t h e hydrologic cycle. This c y c l e a l s o serves a s t h e p r i n c i p a l v e h i c l e of m t t e r and energy i n s i d e t h e ecosystem. The s e t of l i n k s of t h e hydrologic c y c l e , i n f l u e n c i n g t h e l i f e and development of ecosystems, i s formed by t h e hydrometeorological regime, which is c h a r a c t e r i s e d mainly by p r e c i p i t a t i o n , w a t e r q i i a l i t y , groundwater t a b l e , r u n o f f , i c e and sediment d r i f t d a t a , temperature and sunshine. Human a c t i v i t i e s which take p l a c e i n t h e framework of t h e n a t u r a l environment i n f l u e n c e t h e d i f f e r e n t components of t h i s svstem. I f t h i s i n f l u e n c e d i f f e r e n t components of t h e ecosystem

on the

does n o t exceed the l i m i t s of thP homeo-

s t a s i s o f t h e system, t h e system i s a b l e t o achieve t h e o r i g i n a l equilibrium a g a i n i n t h e l o n r t e r m . But o f t e n human a c t i v i t i e s a l s o i n f l u e n c e t h e s t r u c t r i r e of t h e system. These s t r u c t u r a l changes, above a l l t h e change i n t h e water regime (water q u a l i t y , r u n o f f , groundwater tzible, i c e and sediment d r i f t ) , r e s u l t i n sudden o r long-term n e g a t i v e changes, i . e . i n the degradation of l o c a l o r regional ecosystems. The e f f e c t s of human a c t i v i t i e s on t h e hydrologic c y c l e can be d i s t i n g u i s h e d as

( a ) p u r p o s e f u l , i . e . requested consequences of water development p r o j e c t s and measures, (b)

non-requested,

i . e . t h e secondary e f f e c t s o f a c t i v i t i e s which have

another piirpose o r u n i n t e n t i o n a l e f f e c t s . Both t h e s e e f f e c t s can be e i t h e r d e s i r a b l e o r u n d e s i r a b l e . Because of t h e a s y e t uncoordinated economic development on a global s c a l e , t h e undesirable e f f e c t s o f t e n p r e v a i l . The e f f e c t s of human a c t i v i t i e s cause a change i n both t h e quant i t a t i v e and t h e q u a l i t a t i v e a s p e c t s of t h e hydrologic cycle. The q u a n t i t a t i v e and q u a l i t a t i v e a s p e c t s a r e mutually interconnected. A change i n t h e volume of water i n one process of the hydrologic cycle r e s u l t s i n a change i n t h e concent r a t i o n o f d i s s o l v e d and suspended m a t t e r as w e l l , i . e . i n t h e water q u a l i t y . Chanpes i n w a t e r q u a l i t y i n f l u e n c e t h e course o f t h e s e hydrological processes (water p o l l u t i o n decreases t h e i n f i l t r a t i o n and evaporation rate e t c . )

~

thus

2h3 TABLE 4.1 Phenomenon Sirrpli f i e d equation

Remrks

Rain fa 11

k

-

c o e f f i c i e n t of condensation

E

-

evaporation

P = k .E C

Influenced f a c t o r s and causes of t h e i r change k

C

E

P Te S I2

-

Depression and detention storage

k

- detention coefficient

D

A

- area s u r f a c e

Interception

I = P - P e P = R + S - I2

= kd.A

Infiltration -$ 1 v = -- . S t + v,< f 2

.

-

effective rainfall throughfall stemflow l i t t e r interception loss

kd

A

k'

-

kf

-

"Y

-

c o e f f i c i e n t of t h e I unsaturated flow c o e f f i c i e n t of hydr a u l i c conductivity s o i l water p o t e n t i a l kf

kx

-

kx

K

-

ET

. EbJ

= kx

Overland flow Qs = K

. H"

m -

H

Concentrated s u r f a c e ninof f Qr = A vs

.

2

R+ vs=-*

w

n

.[ZgAh+k(vt

c o e f f i c i e n t of the land s u r f a c e - evaporation from f r e e water s u r f a c e

- v;)]

R L

-

n h

-

k

-

%

c o e f f i c i e n t of K rainfall intensity, slope and roughness m depth of flow H c o e f f i c i e n t of flow

-

by changes i n the land s u r f a c e and i n t h e veget a t i v e canopy and l i t t e r

-

changes i n t h e land surface construction of channels and r e s e r v o i r s , s u r f a c e drainage - changes i n t h e area surface

vf - a c t u a l i n f i l t r a t i o n S S - sorptivity v , ~- constant i n f i l t r a tion rate t - t i m e from the beginning of t h e process vk -

C =A.vf g 1 vf = k f . g r a d y

Evaporation and evapotranspiration

-

changes i n energy balance changes i n t h e quantity of condensation nuclei changes i n a i r motion s e e evaporation and evapotranspiration

I,T,S,D

Subsurface runoff

vf = kfl. I

-

changes i n t h e hydraulic cond u c t i v i t y and i n o t h e r s o i l p r o p e r t i e s including the m i s t u r e content and i n t h e overland flow depth Changes i n permeability

-

by changes i n t h e head r e s u l t i n g from water withdrawals, i r r i g a t i o n

- by

clogging e t c .

-

changes i n the land surface including canopy

-

chances i n t h e land roughness and slope r e s u l t i n g changes i n t h e flow r e s u l t i n g changes i n t h e flow depth

-

hydraulic radius v l , v2,R,k,&- change i n t h e chanlength of the stream nel cross s e c t i o n stretch L - changes i n t h e length of the c o e f f i c i e n t of channel s t r e t c h channel roughness n - changes i n the channel d i f f e r e n c e i n water roughness tables reduction c o e f f i c i e n t

Hydrological processes and f a c t o r s of t h e i r equations, influences of human activities.

264 i n f l u e n c i n g the r e l e v a n t q u a n t i t y of water ( T a b . 4 . l ) . The q u a n t i t a t i v e i n f l u e n c e on t h e course of the hydrologic c y c l e is a r e s u l t of

( a ) a n a c c e l e r a t i o n , extension o r f a c i l i t a t i o n of any process of the hydrol o g i c c y c l e i n t h e p a r t i c u l a r space, ( b ) a r e t a r d a t i o n , l i m i t a t i o n , suppression o r d i s c o n t i n u a t i o n of any of the hydrologic processes i n the p a r t i c u l a r space. Such a n extension o r suppression r e s u l t s i n t h e a b s o r p t i o n o r r e l e a s e of energy, thus i n f l u e n c i n g the course o f o t h e r hydrological processes i n s i t u and/ o r i n another a f f e c t e d space.

The q u a l i t a t i v e i n f l u e n c e on t h e course of t h e hydrologic c y c l e i s a r e s u l t of ( a ) an i n c r e a s e o r decrease i n t h e compounds of the hydrologic c y c l e , which have a l s o previously been i t s n a t u r a l component, ( b ) the i n t r o d u c t i o n of such new elements and compounds i n t o the c y c l e and a contingent i n c r e a s e of t h e i r c o n t e n t i n t h e c y c l e . These compounds o r elements may become (a, a n enduring o r temporary accessory component of a l l the processes of the hydrologic c y c l e , t h e i r c o n t e n t being thinned o r decomposed during these processes, ( b ) an enduring component of water r e s o u r c e s , the a i r mass o r t h e l i v i n g m t t e r , t h e i r c o n t e n t beinp g r a d u a l l y accumulated. The change i n any v a l u e of the hydrological d a t a , i n c l u d i n g t h e change i n water q u a l i t y i n d i c a t o r s , can be expressed by t h e equation

91

=

qo

-

qo

+

(m 3

k=l Ak

)

.

m3 s-l

, m.a.s.l.,

g.m-3 )

(4.1)

the n a t u r a l value o f any parameter of t h e hydrologic c y c l e n o t influenced by human activities

41

-

t h e a c t u a l value of the hydrometeorological parameter influenced by human activities

A1, An

-

increments/decrements a r i s i n g from d i f f e r e n t human a c t i v i t i e s

1, 2 ,

......., n

I t i s r a t h e r d i f f i c u l t t o determine t h e exact values of these increments o r decrements. They can be s e p a r a t e l y measured o r a s s e s s e d by some mathematical method, o r by modelling i n exceptional cases only. They are provoked by many f a c t o r s , whose i n f l u e n c e is long-term, v a r i a b l e and sometimes a l s o e r r a t i c .

"heir i n t e r p l a y is extremely d i f f i c u l t t o follow up i n d e t a i l and appears t o be s t o c h a s t i c . T h e i r usual determination is t h e r e f o r e based on a comparison of the n a t u r a l and transformed values k=l rLl- q1

-

qo

(m, m'.s-l,

m.a.s.l., g.m -3 1

(4.2)

265 The increments/decrements have to be assessed by methods of water balance research on experimental r i v e r basins methods of hydrological analogy s t a t i s t i c a l methods mathematical or physical modelling

4.2

comparing data of the a f f e c t e d and non-affected

period

comparing d a t a of the a f f e c t e d and non-affected

s i m i l a r catchment

CHANGES I N THE HYDROLOGICAL BAIANCE To a s c e r t a i n the q u a n t i t a t i v e e f f e c t s of h m n a c t i v i t i e s on the hydrolopic

c y c l e , i t appears p r a c t i c a b l e t o subdivide the area i n

question i n t o elements

which correspond t o , f o r example, r e l e v a n t sub-catchments and t o s e p a r a t e the atmospheric and l i t h o s p h e r i c branch of the hydrologic cycle (Fig. 4.1.).

Qn Gn

Gn-1

Fig. 4.1. Schematic r e p r e s e n t a t i o n of the atmospheric (a) and t e r r e s t r i a l (b) branch of the water cycle: A - input and output of water vapour, P - precipitation, E evapotranspiration, Q - s u r f a c e water discharge, G - groundwater discharge, A G, A E - s t o r a g e , Cn - water consumption

-

Elements of the hydrological balance which r e p r e s e n t the deep percolation and s t o r a g e i n f l o r a and fauna can be omitted to simplify the problem. Bearing t h i s i n mind, t h e hydrologica1 balance in the atmospheric branch of the hydrologic cycle can be modelled by the equation

An-1 Pn

+ En =

- E

Pn En

-

n

An + Pn + AEn

=-E

n

+ A

n-1 - *n

v e r t i c a l and h o r i z o n t a l p r e c i p i t a t i o n i n the element n evaporation

i n the element n

(4.3)

266

-

AF,

increment i n t h e water vapour content i n the atmosphere of the element n

h-l - water

vapour i n p u t of the element n

A, - water

vapour output of the element n .

The balance of t h e l i t h o s p h e r i c branch of the hydrologic cycle can be expressed as follows: Pn

+

Qn-1

+

Gn-1

En + Qn + Gn +ACm + C&

Q,-l

-

surface water inflow

Qn

-

s u r f a c e water outflow

(4.4)

&-1 - groundwater inflow

-

groundwater outflow

AG,

-

increment o r decrement i n the groundwater content

C,

- water

,C

consumption i n s i d e the area i n question

Depending on the hydrological conditions, the terms of t h e equation 4.4 Cm-l and Gn, which express t h e groundwater inflow and outflow, can be omitted because t h e i r d i f f e r e n c e is n o t important. The water consumption G, may a l s o o f t e n be omitted, being mainly the component of the evaporation

G . I n t h i s way, the

equation 4.4 can be s i m p l i f i e d t o

(4.5) Analysing a long-term period, t h e increment i n t h e groundwater storage does n o t change: I n t h i s way

This equation, expressed f o r the o v e r a l l catchment a r e a , can be expressed very

s imp 1y :

(4.7) because i n t h i s case Qn-l = 0. The e x a c t average value of t h e evaporation (and a l s o of the s o i l moisture) cannot be measured and evaluated d i r e c t l y , because i t changes considerably during the day and from place t o p l a c e . They can therefore be derived from the long-term average values of p r e c i p i t a t i o n and surface flow, which a r e measured d a i l y and a r e r e l i a b l e enough. The equations of t h e hydrological balance make i t p o s s i b l e , t h e r e f o r e , t o check the r e l i a b i l i t y and accuracy of the c h a r a c t e r i s t i c averages of the hydro-

267 l o g i c a l parameters. Connecting the equations 4.3 and 4 . 5 i t follows that

and f o r a closed catchment a r e a Gn

=

-En

+

An-1

+

An

-

Qn

(4.9)

Rearing i n mind the s t a b l p water content i n t h e l i t h o s p h e r e and atmosphere over waste a r e a s i n the long-term, the d i r e c t r e l a t i o n of t h e long-term averaEes f o r a b i g catchment i s

Under these conditions, which a r e n o t a p p l i c a b l e f o r short-term d a t a , the s o i l water increment equals the decrease i n t h e humidity i n the atmosphere and vice-versa. Analysing the above equations, the following conditional conclusions can be derived f o r l a r g e catchments: ( a ) As a r e s u l t of an increase i n the outflow from the catchment, the water vapour outcome is decreased, causing a decrease i n the p r o b a b i l i t y of precipit a t i o n occurrence i n the a r e a a f f e c t e d , whose p o s i t i o n depends on the d i r e c t i o n of the p r e v a i l i n g

a i r mss movement. A decrease i n the water outflow causes an

increase i n the mentioned p r o b a b i l i t y (Eq. 4.10). ( b ) As a r e s u l t of an i n c r e a s e i n evaporation i n the catchment, the probab i l i t y of p r e c i p i t a t i o n occurrence i n t h i s catchment i s increased, a s f a r a s the conditions f o r i t s condensation have not changed, i . e . the increase i n evaporation does n o t n e c e s s a r i l y lead t o a decrease i n outflow (Eq.4.7). ( c ) An increase i n outflow decreases t h e average p r e c i p i t a t i o n of the area i n question. A decrease i n outflow increases the p r o b a b i l i t y of i t s occurrence. Equations of the hydrological balance make i t p o s s i b l e t o define a l o t of s i m i l a r conditioned r e l a t i o n s , but the r e s u l t i n g hydrome teorological s i t u a t i o n a l s o depends on the influence of t h e neighbouring a r e a s . The f a c t o r s AE - t h e increment i n water vapour i n the atmosphere - and AG the increment i n the s o i l and groundwater - a c t a s r e g u l a t o r s . The increase i n the vapour content of the a i r leads to i t s oversaturation. The increase i n the water c o n t e n t o f r e s e r v o i r s and s o i l may have the same r e s u l t when the supply of energy enables an increase i n evaporation. Changes i n the hydrologic cycle do n o t , t h e r e f o r e , depend on the hydrological balance alone. They a r e a l s o determined by the b a s i c laws of physics. An a n a l y s i s of t h e q u a n t i t a t i v e influence of man on the hydrologic c y c l e has to be based on the equations of the r e l e v a n t hydrological processes and on changes i n the r e l e v a n t e n t r y data (Tab. 4.1).

268

F i g . 4 . 2 . Basic i n t e r r e l a t i o n s h i p s of t h e main processes i n the atmospheric, l i t h o (and pedo)spheric and hydrospheric system The changes which i n f l u e n c e the elements of t h e hydrologic c y c l e can be categorized i n t o mutually interconnected (a) changes i n the E a r t h ' s s u r f a c e , (b)

changes i n t h e e n e r g e t i c balance,

(c) changes i n f l u e n c i n g the process of p r e c i p i t a t i o n ( F i g . l . 2 ) . The changes i n the E a r t h ' s s u r f a c e - a s the consequences of c l e a r i n g , a g r i -

c u l t u r a l production, u r b a n i z a t i o n , i n d u s t r i a l i z a t i o n and t r a n s p o r t - influence the d i s t r i b u t i o n of t h e volume of water among the d i f f e r e n t processes of the hydrologic cycle: i n t e r c e p t i o n , depression and d e t e n t i o n s t o r a g e , evaporation, i n f i l t r a t i o n , groundwater r u n o f f , d i s p e r s e d and concentrated s u r f a c e r u n o f f . They a l s o i n f l u e n c e t h e i r i n t e n s i t y and pace. The changes i n t h e enerpy balance a s a r e s u l t of human a c t i v i t i e s occur with-

269

i n the framework of the n a t u r a l processes, whose i n t e n s i t y i s enormoiis. I n the f a i r l y regular t r a n s i t i o n s between warm i n t e r g l a c i a l and

p a s t there have been

g l a c i a l years about every 100,000 y e a r s . I n t e r - g l a c i a l periods have been relat i v e l y s h o r t e r , l a s t i n g some 10,000 y e a r s . The present epoque seems t o s t a r t i n next g l a c i a l period. The average global temperature i s a t p r e s e n t + 14.8OC. Man's a c t i v i t i e s increase the energy input i n t o the atmosphere through ( a ) the increasing hothouse e f f e c t of t h e atmosphere a s a r e s u l t of the increasinp q u a n t i t y of carbon dioxide i n the a i r and through p o l l u t i o n of the a i r by o t h e r gases and a e r o s o l s , (b) the h e a t production (Tab. 4 . 2 ) . TABLE 4.2

Mankind ' influence

Time period

E s t i m t e of Relevant the increment surface temperature increment OC

Rate of change towards the end of the time period ('C/decade)

Carbon dioxide

2000 AD

+ 25%

+0.5 t o 2

0.2 to 0.8

content of the

2050 AD

+ 100%

+1.5 to 6

0.3 to 1.2

2000 AD 2050 Ad

0.8 ppbv 2.5 ppbv

+0.1 t o 0.4

0.04 to 0.2

0.25 t o 1

0.02 to 0.1

0.25 to 1

0.02 to 0 . 1

0.5 t o 2

0.05 t o 0.2

?

?

a thmosphere Adding chlorofluorocarbons to the troposphere ~~

Nitrous oxide N 2 0

2050 AD

~

+ 100%

~

content of the a thosphere Direct addition

2100 AD

of h e a t

50-fold increase

?

?

Total expected

2000 AD

-

changes

2050 AD

Adding a e r o s o l s , p a t t e r n s of land use

+

1.2

+

+

4.0

+ 0.7

0.5

S m r y of anthropogenetic influences on the global mean s u r f a c e temperature according to Kellogg (1977). The changes i n the energy balance a r e interconnected with a i r mss movement. They influence not only the evaporation r a t e , but a l s o the water vapour condensation. During t h i s second process, the l a t e n t h e a t of vaporization/fusion

270 is r e l e a s e d

. Thus,

precipitation is conditioned n o t only by the presence of

condensation n u c l e i , b u t a l s o by the t r a n s f e r of t h i s l a t e n t h e a t to o t h e r a i r masses. The changes i n the energy input a l s o depend on changes on the E a r t h ' s surface. Changes i n the s o l a r r a d i a t i o n absorbed by the surface have an e f f e c t on the h e a t balance, a s w e l l a s on the l o c a l climate. They a r e completely heterogeneous, a s a r e t h e i r consequences, too, r e s u l t i n g from the influence of o t h e r f a c t o r s . TABLE

4.3

Land s u r f a c e

Albedo ( X )

Snow: f r e s h

85 70 30-65

old me1 t i n g Water (depending on the angle of incidence )

2-78

Chalk and limestone (white)

45 12-18

S i l i c e o u s sand(white,yellow) dry 34-25 wet 29 Clay dry wet

Albedo (%)

Forest : deciduous i n autumn i n spring oak i n s p r i n g & summer pine f o r e s t spruce fir

S o i l and rocks:

Granit and s i m i l a r rocks

Land s u r f a c e

33-38 16-27 18 6-19 14 10

Grassland: dry green

16-30 8-27

Fields : Cereals(depending on ripeness) 10-25

29-3 1

ploughed dry

16

ploughed w e t

12-20 5-14

Albedo, the c o e f f i c i e n t of the r e f l e c t a n c e of s o l a r e n e r w according to Lamb

(1972). An increase i n the surface m i s t u r e and a change i n the colour of the e a r t h ' s

surface from b r i g h t t o dark, f o r example, causes a decrease i n the albedo (Tab.

4.3). Flooding m y cause by i t s water t a b l e a n increase i n the albedo, depending on the angle of d i p of the h e a t rays. A g r i c u l t u r a l a c t i v i t i e s influence the albedo n o t only through the type of p l a n t , but a l s o through r e l e v a n t a g r i c u l t u r a l p r a c t i c e s . Thus, wan's a c t i v i t i e s both increase and decrease the value of the albedo. The chain of consequences (Fig.4.4) depends on many l o c a l f a c t o r s , while the r e s u l t i n g consequences may be q u i t e d i f f e r e n t . I n t h e case of t h e i r important influence on the h e a t balance of t h e Earth, they m y even cause important changes in distant areas. The t h i r d category of changes t o a f f e c t the hydrologic cycle includes f a c t o r s which d i r e c t l y influence t h e process of p r e c i p i t a t i o n , such a s :

271 (a)

changes i n the s o i l and a i r humidity, a r i s e i n the number of condensation n u c l e i , r e s u l t i n g i n increased

(b) p r e c i p i t a t i o n i n the d i r e c t i o n of the a i r mass movement from the e n t r y of the pollution, ( c ) r a d i o a c t i v e elements (Krypton K r , T r i t i u m T r , Radon Rn and o t h e r products of Uranium U ) , e n t e r i n g t h e atmosphere n o t only a s a r e s u l t of the generation of nuclear power and e n r i c h i n g the nuclear f u e l , b u t a l s o through the incomplete combustion of l o w q u a l i t y coal. An i o n i z a t i o n of the mentioned elements increases the e l e c t r i c a l conductivity of the a m s p h e r e , decreasing i t s e l e c t r i c a l charge. Rain can occur under a s t r o n g e l e c t r i c a l char* of clouds only. The occurrence of r a d i o a c t i v e gases i n the atmosphere decreases the p r o b a b i l i t y of r a i n occurrence and i t s i n t e n s i t y . The e f f e c t of the mentioned f a c t o r s m y a l s o be contradictory: the a i r pollut i o n aggravates the condensation of the water vapour by increasing i t s temperat u r e , b u t simultaneously forms t h e condensation n u c l e i which f a c i l i t a t e t h i s process. Owing t o these complicated r e l a t i o n s h i p s and feedbacks, the course of hydrological processes and the influence of anthropogenetic f a c t o r s a r e remrkably s t o c h a s t i c : D i f f e r e n t consequences correspond t o i d e n t i c a l causes, each of them having a d i f f e r e n t p r o b a b i l i t y of occurrence, depending on the influence of the o t h e r elements of the system. INFLUENCE OF FORESTRY AND AGRICULTURE

4.3

Vegetative canopy a s a component o f t h e s t r u c t u r e of the hydrologic system influences the a v a i l a b i l i t y of water resources and the negative e f f e c t s of water occurrence. D i f f e r e n t types of vegetation, the d e n s i t y and s t r u c t u r e of the growth, the topography of the s u r f a c e , the q u a l i t y and q u a n t i t y of the l i t t e r , humus and s o i l l a y e r have a considerable e f f e c t on ( a ) the short-term r e t e n t i o n , whose consequence is a decrease i n flood discharges, (b) the long-term accumulation, whose consequence is a decreased f l u c t u a t i o n i n runoff and increased minimum discharges, ( c ) the p r o t e c t i o n of the land surface a g a i n s t e r o s i o n , (d) the water q u a l i t y . This e f f e c t c o n s i s t s i n ( a ) decreasing the concentration of the s u r f a c e runoff and i t s v e l o c i t y , (b) changing the dispersed s u r f a c e runoff from the n a t u r a l recharge of prec i p i t a t i o n to groundwater runoff, (c)

slackening the pace of the melting of snow,

(d)

causing water l o s s e s through high evapotranspiration,

(e)

catching the h o r i z o n t a l r a i n f a l l i n mountainous a r e a s .

272

Hv

F i g . 4.3. Retention, r e t a r d a t i o n and anti-erosion e f f e c t of the biosphere and i t s influence on r a i n f a l l and evaporation: ( a ) region w i t h vegetative cover, (b) region without vegetative cover: Pev iPh < P,; Qmxv << Qmaxh; E v > Eh;

Iev

Iek,;

HV

min Gh

Hh;

<

min Gv.

I n t h i s way v e g e t a t i v e canopy i n f l u e n c e s , i n p a r t i c u l a r , (Fig.4.4)

#nax

flood discharges minimum discharges

Qmin

t o t a l annual runoff

Qa

the groundwater regime the e r o s i o n process and i t s i n t e n s i t y

Gg

the water q u a l i t y

ql-n Pa

t o t a l annual r a i n f a l l

Ie

and the r a i n f a l l occurrence P The i n t e r r e l a t i o n s h i p of these e n t r y data of the runoff process and of the r a i n f a l l can be expressed by the equation Qlpax, Qmin, Q a , Gg, I,, 91-n

=

P

.

fl-6 (Xc,X,Js,X~,Xg,X~)

(4.11)

Xc - climatological f a c t o r , including the energy i n p u t ,

Xv Xs

-

f a c t o r of the vegetative canopy, depending on i t s composition, age and s t a t e s o i l f a c t o r , depending on t h e s o i l type, s t r u c t u r e and permeability, charect e r i z e d by the course of t h e s u c t i o n pressure o r by the s a t u r a t i o n and the c o e f f i c i e n t of the hydraulic conductivity,

Xm - morphological f a c t o r , including t h e shape of the s l o p e and its p o s i t i o n , b u t a l s o the l o c a t i o n of erosion r i l l s and channels,

XR - geological f a c t o r , including the s t r u c t u r e and permeability of t h e geolog i c a l formations and t h e i r communication with the land s u r f a c e ,

Xx - water management

f a c t o r , including a l l o t h e r p o s i t i v e and negative influ-

ences t o a r i s e from human a c t i v i t i e s , e.g. from the production of h e a t , land and s o i l management, mining, thus having an impact on a l l previous factors.

273

I J

I DEFORESTATION

OF TROPICAL A R E A S

INCREASED A L B E D O

DECREASE IN ENERGY INPUT

DECREASE IN EVAPORATION AND RADIATION OF ENERGY FROM L A N D SURFACE

DECREASE IN AIR MOTION AND PRECIPITATION

1

D E C R E A S E D TRANSFER OF T H E L A T E N T HEAT COOLING OF THE M I D D L E A N D UPPER TROPOSPHERE I N TROPICAL A R E A S

I

SOUTHERN A N D NORTHERN LATITUDE, DECREASE OF THE EQUATOR TO P O L E TEMPERATURE GRADIENT

DECREASE I N H u t i i D i T Y A*T,,, DIRECTION OF MERIDIANS

T R A N S F E R IN T H E

GENERAL DECREASE I N TEMPERATURE A N D P R E C I P I T A T I O N B E T W E E N 45 A N D 8 5 O O F T H E N O R T H E R N 40 A N D 6 0 ° 0 F THE SOUTHERN L A T I T U D E

Fig. 4 . 4 . Chain of consequences of d e f o r e s t a t i o n i n t r o p i c a l regions according to P o t t e r e t a l . (1975). The i n t e n s i t y of hydrological processes on the boundary of the pedosphere and atmosphere can a l s o be derived from the material and enerrry balance of the r e l e v a n t ecosys tern. I n t e r c e p t i o n i s a l s o important, depending on the composition of the v e g e t a t i v e canopy, i t s age, d e n s i t y and s t a t e and on climatological fact o r s , e s p e c i a l l y on the r a i n f a l l regime. T r a n s p i r a t i o n , depending on the biomass q u a n t i t y and a l s o on the c h a r a c t e r i s t i c s of t h e vegetative canopy, is f a r l e s s impor tan t . The influence of the vegetative canopy on the hydrologic cycle can be charact e r i z e d by simple parameters such as i t s composition, d e n s i t y , h e i g h t and volume i n the

system of the atmosphere and by the d e n s i t y and depth of t h e r o o t system

i n the pedosphere. But o t h e r i n t e r r e l a t e d f a c t o r s , such a s pedological, geologic a l and topographical f a c t o r s , may exceed t h e i r importance under s p e c i f i c local conditions of change i n the vegetative canopy. Due t o these complex i n t e r -

274 r e l a t i o n s h i p s , changes

i n the vegetative canopy over v a s t a r e a s m y a l s o provoke

global consequences (Fig. 4 . 5 ) .

4.3.1

I n t e r c e p t i o n , Evapotranspiration

and I n f i l t r a t i o n

The e x t e n t of i n t e r c e p t i o n depends very much on the c h a r a c t e r i s t i c s o f the vegetation. The d i f f e r e n c e between the s m e r and winter values and t h e i r averages depends on t h e type of p r e c i p i t a t i o n , r a i n f a l l and snowfall. I n f o r e s t s a t low a l t i t u d e s i n t e r c e p t i o n i s an important negative component of the water balance. Under conditions of p r e v a i l i n g evaporation, i n t e r c e p t i o n decreases the t o t a l r u n o f f . A t higher a l t i t u d e s , when h o r i z o n t a l p r e c i p i t a t i o n from mountain fogs p r e v a i l s , i n t e r c e p t i o n increases the t o t a l p r e c i p i t a t i o n : d r i p and stemflow exceeds the value of evaporation of the i n t e r c e p t e d water. (Tab. 4 . 4 ) . TABLE 4.4 ~~

Precipitation ( seas on)

650 m ( s u m e r ) 550 mn (winter) Rainfall intensity

Low Medium High

-

I n t e r c e p t i o n (%) Young growth

Pole tree

Timber tree

Noble tree

12

20

10

22

30 26

39 32

Spruce

Beech

81.7 54.8 24.1

71.9 24.8 17.7

Increase i n average i n t e r c e p t i o n with the age of t h e v e g e t a t i v e canopy according t o Delfs (1956) and values of t h e a c t u a l i n t e r c e p t i o n i n coniferous and deciduous f o r e s t s (%) according t o Eidmn (1968). The a c t u a l t r a n s p i r a t i o n of t h e vegetation depends on the r a i n f a l l , the a v a i l a b i l i t y of water i n the s o i l , the energy i n p u t , and t h e q u a n t i t y and funct i o n of t h e biomass. D i f f e r e n t species of v e g e t a t i o n , e . g . a g r i c u l t u r a l products have d i f f e r e n t water requirements, depending on t h e i r s t n x t u r e , e s p e c i a l l y on the r s t i o of t h e i r underground and s u r f a c e p a r t s .

The water requirements of wood

species do n o t d i f f e r as much. The difference

between the water requirements of hardwood and softwood, of quickly and slowly growing l o c a l wood species i n Central European conditions i s reported t o be comparatively small, f o r water requirements depend on the d e n s i t y and development stage of t h e r e l e v a n t wood: they i n c r e a s e noticeably with age. Only some e x o t i c s p e c i e s a r e reported t o have low water requirements, but not e x o t i c i n d u s t r i a l wood, which i s r a r e l i k e l y t o be planted i n these conditions.

275 The l e v e l of evapotranspiration i n f o r e s t s i s , under c u r r e n t climatological conditions, higher than t h a t of o t h e r types of vegetative canopy, depending not only on the wood species and the v a r i e t y of d i f f e r e n t s t o r i e s of o t h e r p l a n t s , but a l s o on f o r e s t r y p r a c t i c e s . Actual evapotranspiration from highly productive a g r i c u l t u r a l land i s lower, under t h e same c l i m t o l o n i c a l conditions, than the evapotranspiration of a f o r e s t with r a t i o n r a t i o of f o r e s t on the

l i t t l e wood production. The evapotranspi-

and a g r i c u l t u r a l land depends t o a s i g n i f i c a n t e x t e n t

energy input required t o evaporate t h e t o t a l y e a r l y r a i n f a l l (Fig. 4.5).

TROPIC, TUNDRA

D R Y , SUBTROPIC

Jt

Fig. 4.5. The r a t i o of evaporation from f o r e s t s Ef and from f i e l d s E, i n r e l a t i o n t o the r a t i o of the energy i n p u t Jef and the energy J t needed t o evaporate the t o t a l yearly r a i n f a l l P according t o Rudyko (1973).

Two b a s i c t h e o r e t i c a l , but contradictory cases of the water mamgement function

3f

s o i l and vegetative canopy

can be distinguished:

( a ) The i n f i l t r a t i o n increases with the growing accumulation c a p a b i l i t y of the s o i l and the v e q e t a t i v e canopy, ( b ) The i n f i l t r a t i o n r a t e decreases with the growing accumulation capacity of the s o i l and vegetative l a y e r .

I n the f i r s t case of a simultaneous increase i n the i n f i l t r a t i o n and accumul a t i o n c a p a c i t y , the amount of the evaporated r a i n f a l l grows with the increasing accumulation c a p a c i t y , thereby reducing the s u r f a c e runoff. In such s o i l s

the

h i g h e s t groundwater runoff occurs a t medium values of i n f i l t r a t i o n and accumul a t i o n , and runoff f o r both high and low values of i n f i l t r a t i o n and accumulation decreases t o almost zero. In such s o i l s , given

s u f f i c i e n t supply of energy, the high i n f i l t r a t i o n r a t e enables almost a l l s o i l water t o be evaporated. The

surface

r u n o f f , whose values decrease with the increase i n evaporation (Fig.

4 . 6 ) , is supplemented by the groundwater runoff rrainly f o r medium values of i n f i l t r a t i o n and accumulation. I n the second case,

where the i n f i l t r a t i o n r a t e of the s o i l cover is low,

although i t s accumulation capacity is high, most of the r a i n f a l l flows away a s

276

Fig. 4 . 6 . The t h e o r e t i c a l impact of perviousness and of the accumulating e f f e c t of the s o i l l a y e r on t h e d i s t r i b u t i o n of the r a i n f a l l P a t s u r f a c e runoff Qs, groundwater runoff Gg and on the formation of r i v e r discharges Qr and evaporat i o n E according t o h o w i t c h (1970). dispersed or Concentrated surface runoff. The values of both groundwater runo f f and evaporation a r e low f o r low i n f i l t r a t i o n r a t e s . With the growing i n f i l tration

r a t e and simultaneously decreasing accumulation capacity, the dispersed

s u r f a c e runoff decreases and t h e groundwater runoff increases. Evaporation is low f o r both high and low values of i n f i l t r a t i o n : the r a i n f a l l changes i n t o surface runoff o r p e r c o l a t e s i n t o lower geological l a y e r s . The h i g h e s t evapor a t i o n values and the lowes values of t h e concentrated runoff occur a t medium values of i n f i l t r a t i o n and accumulation. Under conditions of a l o w i n f i l t r a t i o n r a t e of t h e s o i l , the s u r f a c e runoff concentrates without any important influence of the groundwater runoff. TJnder conditions of a high i n f i l t r a t i o n r a t e , the surface runoff concentrates with an important i n f l u m c e of the groundwater: the f l u c t u a t i o n of i t s values is smaller, provided the accumulation capacity of the s o i l i s s u f f i c i e n t . The above a n a l y s i s was based on a t h e o r e t i c a l hypothesis of s t a b l e physical, chemical and b i o l o g i c a l p r o p e r t i e s of the s o i l l a y e r and the vegetative canopy. I n r e a l i t y , these p r o p e r t i e s depend on t h e s o i l s t r u c t u r e and its state, a s well a s on the development s t a g e of the vegetation and i t s s t a t e . Cultivated agric u l t u r a l land u n d e r p e s comparatively more important and more frequent changes than f o r e s t land, which u n d e r s e s b a s i c changes during c l e a r i n g . The changes of the a g r i c u l t u r a l land a r e seasonal, depending on the p a r t i c u l a r c u l t i v a t i o n practices. The i n f i l t r a t i o n p r o p e r t i e s of a g r i c u l t u r a l land a r e a f f e c t e d e s p e c i a l l y by ploughing, and depend t o a l a r g e e x t e n t on the duration of t h e period between ploughing and r a i n f a l l . Primitive ploughing loosens the s o i l till down t o a depth of 0.12 m, horse ploughing t o 0.16 m , and mechanized ploughing t o 0.3 m. ploughing slows down the winter r u n o f f , changing a s u b s t a n t i a l

Mechanized autumn

277 p a r t of the surface runoff i n t o gromdwater runoff, simultaneously increasinp the volume of the s t o r e d r a i n f a l l and snowfall. This P o s i t i v e influence can be reduced o r d i s t o r t e d by the weight of t r a c t o r s packinp the lower s o i l l a y e r s . The e x t e n t of the influence of mechanized ploughing on the i n f i l t r a t i o n r a t e depends n o t only on the s t a t e of a r g r e g a t i o n , but a l s o on the climate and the nature of the p r e c i p i t a t i o n . I t appears t o be more important i n a r e a s with a low t o t a l y e a r l y r a i n f a l l and a low s o i l humidity. Concerning the influence of p l a n t s p e c i e s , the continuous cultivation

of c e r e a l s decreases the i n f i l t r a t i o n

r a t e to a minimum value. The

e f f e c t of the c u l t i v a t i o n of c e r e a l s i n r o t a t i o n is more favourable from t h i s p o i n t of View, and t h e c u l t i v a t i o n of fodder crops i n r o t a t i o n most favourable of a l l . The i n f i l t r a t i o n r a t e of pastures and f o r e s t s tends, on average, t o exceed t h i s property of a m i c u l t u r a l o r urbanized land. These lands d i s t i n g u i s h thems e l v e s from the a p r i c u l t u r a l land by t h e i r extensive and dense root system. I n f o r e s t s , not only species of the lower p l a n t s t o r i e s and the l i t t e r l a y e r cont r i b u t e t o t h i s property, b u t a l s o the favourable biochemical p r o p e r t i e s of the f o r e s t s o i l , which generally has a good s t r u c t u r e and a high humus content. The i n f i l t r a t i o n p r o p e r t i e s of f o r e s t land a l s o depend on the p l a n t species

and t h e i r age, a s w e l l a s on c u l t i v a t i o n and c l e a r i n g p r a c t i c e s . The h i g h e s t i n f i l t r a t i o n r a t e is produced by t h e s o i l of mixed tive

property i n comparison with a g r i c u l t u r a l and

helped by

f o r e s t c u l t u r e s . This posipasture land is f u r t h e r

the less s i g n i f i c a n t e f f e c t of f r e e z i n g , which penetrates i n t o the

upmost s o i l l a y e r only.

4.3.2

Influence of the Vegetative Canopy on Floods and Erosion

The r a t e of surface

runoff depends e s p e c i a l l y on the topography, the i n f i l -

t r a t i o n r a t e and, t o a lesser degree, a l s o on i n t e r c e p t i o n l o s s e s . On agricultural

lands these p r o p e r t i e s

depend on the a g r i c u l t u r a l p r a c t i c e s , especially

on the depth and method of ploughinp, a s w e l l a s on t h e p l a n t species and t h e i r development s t a g e . I n f o r e s t s s u r f a c e runoff

i s almost imperceptible, even a f t e r

heavy r a i n s . I n spruce and deciduous f o r e s t s surface runoff m y appear under extreme topographical and s o i l conditions and during heavy r a i n s , when the, s o i l and l i t t e r l a y e r is destroyed by improper c l e a r i n g p r a c t i c e s . The p r o t e c t i v e e f f e c t of the vegptation canopy form of accumulation and ret a r d a t i o n . The accumulation e f f e c t , o r s t o r a g e of water, i s a l s o aided by the r o o t system and the depth of t h e s o i l l a y e r . The r e t a r d a t i o n of the runoff i s caused by t h e

change of the s u r f a c e runoff i n t o groundwater r u n o f f , by the

i n t e r c e p t i o n of the p l a n t s and l i t t e r , and by the roughness of the land surface. This e f f e c t a l s o decreases the erosion r a t e and the concentration of the surface runoff. I n

f o r e s t s the concentration of surface runoff i n t o r i l l s and channels

occurs l a t e r

than on p s s t u r e s and a g r i c u l t u r a l land (Fig. 4 . 8 ) .

278

0.

P

. d.

C.

Fig. 4.7. The impact of v e n e t a t i v e canopy on the rainfall-runoff process: ( a ) multistage f o r e s t , (b) s i n g l e stage f o r e s t , ( c ) grassland and f i e l d s , (d)urbanized a r e a . The values of the r e l e v a n t hydrological phenomena a r e proportional t o the width of r e l e v a n t arrows: Pa = p b > P c < P d ; E a > % > E c > E d ; Q s a < Q s b < Q s c < Q s d ;G a > C;b’ G c ) d ‘ Q b < Q a Hb> H c > Hd P - p r e c i p i t a t i o n , H - vapour condensation, E - w a p o r a t i o n , QS - surface r u n o f f , G - poundwater r u n o f f , 9 - t o t a l runoff and maxirnuni discharges.

n

Accumulation on a f f o r e s t e d land occurs to a more s i g n i f i c a n t e x t e n t during lower r a i n f a l l and runoff than during extreme r a i n f a l l and maximum floods. Floods with a one y e a r frequency of occurrence may increase a f t e r c l e a r i n g more than t e n times

and floods with a hundred

y e a r frequency of occurrence s e v e r a l times,

i n i n h e r e n t dependence on t h e s i z e of the catchment, the depth of the s o i l and i t s moisture before the r a i n f a l l . Forests with shallow s o i l s have no important i n f l u e n c e on the decrease i n discharges i n comparison with deforested a r e a s . The accumulation and r e t a r d a t i o n e f f e c t l a r g e l y depends on the s a t u r a t i o n of the s o i l s , i . e . on the frequency of r a i n occurrences and on the i n t e r v a l between them. I f the accumulation capacity is exceeded, t h i s causes a n immediate increase in

the s u r f a c e runoff.

The water management function of f o r e s t s depends considerably on h m n a c t i v i t i e s and e s p e c i a l l y on f o r e s t management. IJndis turbed f o r e s t c u l t u r e s a r e character-

279 ized by t h e i r important

protection effects

a e a i n s t floods and erosion. Multi-

s t o r e y f o r e s t s c u l t u r e s transform floods more e f f e c t i v e l y than c u l t i v a t e d s i n g l e s t o r e y monocul t u r e s , and f a r more

efficiently

than pastures o r

cultivated

a g r i c u l t u r a l land (Fig. 4 . 8 ) .

600

400

200

0

C A N O P Y REDUCTION

Fig. 4 . 8 . (a) The increase i n the t o t a l annual s u r f a c e runoff and i n the f l u c t u a t i o n of discharges a s a consequence of c l e a r i n g an a f f o r e s t e d catchment according t o Zelen9, KPeEek and Kretmer (1979); p - the decrease i n the biomass ( % ) , Qr - t o t a l y e a r l y r u n o f f , ()f - flood discharfres. (b) The increase i n t h e t o t a l annual runoff Qa as a consequence of c l e a r i n g accordine to Rosch and Hewlett (1982): 1 - coniferous, 2 - deciduous, 3 - bush.

Mechanized

c l e a r i n g , the t r a n s p o r t of timber and the network of t r a n s p o r t

c o m n i c a t i o n s decrease t h i s p o s i t i v e function. The a c t i v i t i e s of c l e a r i n g , tend t o compact the s o i l , destroying

h a r v e s t i n g , t r a n s p o r t and o t h e r machines

i t s s t r u c t u r e , which is conducive t o i n f i l t r a t i o n , both i n f o r e s t r y and agric u l t u r e . The movement of t r a n s p o r t machines, such a s f o r towing logs, form

r i l l s , g u l l i e s and channels f o r t h e concentration of surface r u n o f f , whose increased

tractive

force a c c e l e r a t e s the erosion process.

The d i r e c t r e l a t i o n s h i p between t h e runoff c o e f f i c i e n t and s o i l wash and t r a n s p o r t was proved by means land grading f o r the

of measurement. Murzaev (1977) i n d i c a t e s t h a t the

mechanized a f f o r e s t a t i o n increases the runoff c o e f f i c i e n t

of f o r e s t land by up to 0.8 (Tab. 4 . 5 ) . VeEetative canopy forms an e f f e c t i v e p r o t e c t i o n a g a i n s t

erosion f o r the land

s u r f a c e . The b e s t p r o t e c t i o n i s formed by n a t u r a l ecosystems. The r e s i s t a n c e of c u l t i v a t e d f o r e s t s without

comprehensive anti-erosion measures i s r e l a t i v e l y

s m a l l e r , because of t h e i r gecmetrical arrangement, monotonous p l a n t species and human a c t i v i t i e s during t h e i r c u l t i v a t i o n . an e f f i c i e n t

4.6).

Nevertheless, f o r e s t s generally form

p r o t e c t i o n a g a i n s t erosion, i f n o t destroyed by harvesting (Tab.

2 80 TABLE 4.5

croup

characteris tics

I

F o r e s t s of c a t c h ments used f o r

Water E~Mgeme tn function

Timber production

superior

inferior

Piirpose

Exclude s o i l e r o s i o n , n o t

rmmicipal w a t e r

t o r e s t r i c t runoff , s a f e guard the water q u a l i t y

supply F o r e s t i n zones of

Ia

s a n i t a r y protec-

exceptional conditioned

t i o n of water quality Forests in

I1

balanced

Balance the runoff fluctuat i o n , p r o t e c t the land

upper catchmen ts

a p a i n s t erosion

111

111-1

protectinp

S o i l p r o t e c t i o n , r i v e r bed

canopy

IIIa IIIb

IIIc

s t a b i l i z a t i o n , bank protec-

Rank. canopy

e x r e n t i o n a l condi tioTed t i o n , s a n i t a r y p r o t e c t i o n

Canopy protectin:. loca 1 water

of l o c a l water resources, exceptional conditioned t r a n s f o m t i o n of s u r f a c e

resources I n f i 1t r a t i o n forest belts

water i n to groundwater runoff excepticnal conditioned

Cateporization o f f o r e s t canopy a s a function of i t s water wnagenient function according t o KreEmer and BPle (1975).

Pastures have s i m i l a r p o s i t i v e e f f e c t s , i f n o t destroyed by being o v e r n a z e d o r trampled d m by herds. The r e s i s t a n c e of c u l t i v a t e d f i e l d s a g a i n s t e r o s i o n

is s u b s t a n t i a l l y Imier. The a n t i - e r o s i o n e f f e c t s of the v e g e t a t i v e canopy have a favourable e f f e c t on the q u a l i t y o f t h e s u r f a c e water. Its high i n f i l t r a t i o n c a p a b i l i t y s i m i l a r l y influences the proundwater of eroded m a t e r i a l i n w a t e r in brooks, creeks

q u a l i t y . The decreased e r o s i o n decreases the volume , thereby reducinp the d u r a t i o n of water t u r b i d i t y

and r i v e r s

. The

seven times due t o d e f o r e s t a t i o n .

c o n t e n t of sediments m y increase f i v e t o

Also important a r e o t h e r changes i n water

281

TABLE 4.6 t / 106 b 2 / y r

l a n d use

8.5

Forest

85

Grassland Abandoned s u r f a c e mines

850

Cropland

1700

Harvested f o r e s t

4250

Active s u r f a c e mines

17 000

Construction

17 000

Relative to forest = 1

1 10 100 200 500

2000 2000

R e p r e s e n t a t i v e r a t e s of e r o s i o n from various land uses according t o Canter (1983) quality a f t e r

clearing,

caused by the

decay of orpanic

increased l e a c h i n g of nutriments: - the i n c r e a s e i n the c o n c e n t r a t i o n of n i t r i d e s e . g . from (Hubbard Brook - IJSDA F o r e s t S e r v i c e 1975)

-

m a t t e r and by t h e lmg/l t o 60-80 mg/l

the i n c r e a s e i n the phenol c o n c e n t r a t i o n t o 0.6 m g / l (Kyomiqe,

Hart e t . a l . ,

1981).

-

f i v e t o t h i r t y f o l d i n c r e a s e i n the calcium, mgnesium and

potassium content

i n t h e outtlow (Sopper, 1975). The i n f l u e n c e of a q r i c i i l t u r e and s i l v i c u l t u r e on f l o o d s , e r o s i o n and water q u a l i t y can be mnaged, i n p a r t i c i i l a r : ( a ) by the s e l e c t i o n of s u i t a b l e p l a n t s and woods and by the arrangement of r e l e v a n t c u l t u r e s and p l o t s , and of the c o m n i c a t i o n and drainage network, by s u i t a b l e c u l t i v a t i o n p r a c t i c e s , namely by ploughing a l o n g isohyets and horizontal f r i r r m s , by sowing without plouging, by the r e s t r i c t i o n of land c u l t i v a t i o n , by a r a t i o n a l crop r o t a t i o n , by

c i i l t i v a t i o n i n s t r i p s , by i n f i l t r a t i o n s t r i p s

arranged a l o n g water c o u r s e s , by the

p r o t e c t i v e c u l t i v a t i o n of g r a s s , by wind

b e l t s , i n f i l t r a t i o n and overshadowing of f o r e s t b e l t s , c u l t i v a t i o n of r i l l s , by t e r r a c e s , d i k e s , channels and by

p r o t e c t i n g t h e d e s t r u c t e d land s u r f a c e to

l i m i t erosion, ( b ) by measiires which l i m i t the compacting of the s o i l s u r f a c e and improve the s o i l q u a l i t y and humus content s o a s t o i n c r e a s e the r a t e and t h e degree of e x p l o i t a t i o n of mineral

fertilizers,

by the c u l t i v a t i o n o f r e s i s t e n t f o r e s t c u l t u r e s , which remain s t a b l e i n

(c) winds and d i f f i c u l t snow and i c e c o n d i t i o n s , by pref f e r i n g s e l e c t i v e and p a r t i a l c l e a r i n p , and by t h e inmediate r e c u l t i v a t i o n of c l e a r i n g s i n vast a r e a s .

282 4.3.3

Influence of the Vegetative Canopy on R a i n f a l l and Runoff

The roughness of the f o r e s t cover, higher i n comparison with deforested a r e a s , has an important influence on the p r e c e p i t a t i o n process. I t decreases the r a t e of motion of the lowest l a y e r of the atmosphere and causes turbulence of the a i r , thus improving t h e conditions f o r the condensation of t h e water vapour. This influence has been proved n o t only t h e o r e t i c a l l y ,

but a l s o s t a t i s t i c a l l y , hcw-

ever f o r extremely v a s t f o r e s t a r e a s only. Kalinin (1968) mentions t h a t the influence of l a r g e pine f o r e s t s increases the level of p r e c i p i t a t i o n by about

20% i n the sumner season and by some 8-10% i n winter. The impact of deciduous and mixed f o r e s t s can be estimated a t about one h a l f of the above values. The influence of spruce f o r e s t s is higher, assessed a t a roughly 30% increase i n p r e c i p i t a t i o n i n the sumner season i n comparison with deforested a r e a s . This positive influence on r a i n f a l cannot be considered i n a r e a s With s c a t t e r e d , rel a t i v e l y small f o r e s t s . I n a d d i t i o n t o t h i s , f o r e s t s increase h o r i z o n t a l p r e c i p i t a t i o n , depending on the a l t i t u d e and d i s t a n c e from the sea. F o j t and KreEmer (1976) estimated, f o r c e n t r a l European conditions and mountanuous humid a r e a s , the influence of f o r e s t s a s having a supplement of almost 400 mn t o the values of v e r t i c a l r a i n f a l l i n comparison with deforested a r e a s . Karpov (1962) estimated the value of annual h o r i z o n t a l p r e c i p i t a t i o n by a 13%increase i n the yearly t o t a l r a i n f a l l (Fig.

4.7). The influence of f o r e s t s on a i r motion has a remarkable e f f e c t on snowfall d i s t r i b u t i o n . Snow accumulates i n f o r e s t s t o the detriment of deforested p l o t s . Roughton1(1970) mentions the following fundamental p o i n t s : ( a ) Snow accumulates mainly i n small openings i n f o r e s t s , e s p e c i a l l y a t l m e r a l t i t u d e s . The optimum s i z e of opening f o r snow accumulation i s about one t o ten

times the h e i g h t of the surrounding f o r e s t cover. Targe openings do not have such a p o s i t i v e i n f l u e n c e because of the wind e f f e c t . (b) The e f f e c t of f o r e s t s on snowfall i s more a r e d i s t r i b u t i o n of the snow, r a t h e r than any o v e r a l l i n c r e a s e i n p r e c i p i t a t i o n . It appears a s a p o s i t i v e supplement t o the water balance i n smll catchments only. The r e d i s t r i b u t i o n of snow i n t o deeper f a l l s over smaller a r e a s attenu-

(c)

ates

t h e runoff from t h e melting of the s n m , thus decreasing the s p r i n g peak

discharges, Forests with i n t e r m i t t e n t deforested p l o t s have a favourable e f f e c t on extending the duration of t h e s n m melt. The decreased r a t e of melting c o n t r i b u t e s t o the good accurmilation and r e t a r d a t i o n function of f o r e s t s , m n i f e s t a t e d by a more s t a b l e regime of noundwater, springs and s u r f a c e water. The runoff from a f f o r e s t e d a r e a s is g r e a t l y influenced by the high evapotranspiration

of ecosystems , generally

exceeding t h e c o n t r i b u t i o n of the increased

2 83 precipitation.

The i n c r e a s e i n t h e t o t a l y e a r l y runoff from a f o r e s t e d a r e a s i n

comparison w i t h a r e a s without f o r e s t has been s t a t i s t i c a l l y determined only f o r extremely l a r g e catchments w i t h moderate e v a p o t r a n s p i r a t i o n a s a consequence of h i g h e r v e r t i c a l and h o r i z o n t a l p r e c i p i t a t i o n . I n the c a s e of small a f f o r e s t e d a r e a s a lower y e a r l y runoff has been statist i c a l l y documented i n comparison w i t h a r e a s of the same s i z e and c h a r a c t e r , but without f o r e s t s , a s a consequence of h i g h e r e v a p o t r a n s p i r a t i o n . ‘lc Arthur and Cheney (1965) have measured a n i n c r e a s e i n the t o t a l y e a r l y runoff of between 43 and 235 of t h e h y p o t h e t i c a l runoff of the a f f o r e s t e d catchnent a f t e r a f o r e s t f i r e . Higher values have been measured i n t h e f i r s t years

a f t e r a con-

f lagra tion. The v a l u e s of t h e i n c r e a s e i n the t o t a l y e a r l y runoff due t o d e f o r e s t a t i o n depend n o t only on the percentage of the r e d u c t i o n i n the f o r e s t cover and i t s type ( c o n i f e r o u s , deciduous, b u s h ) , but also on the t o t a l annual p r e c i p i t a t i o n and i t s state of

aggreqation ( F i g . 4 . 9 ) .

The impact of the s i l v i c u l t u r a l a c t i v i t i e s on the runoff c o e f f i c i e n t c depends on t h e following groups of f a c t o r s

(4.12)

c

=

L

-

S

1

-

s i l v i c u l t u r a l p r a c t i c e s and conservation s e r v i c e s , namely the s t a n d d e n s i t y ,

S2

-

ratio

IPS(L’S1,S*,

R1’R2,P)

s t a b l e l o c a l f a c t o r s , e s p e c i a l l y t h e drainage a r e a shape and s l o p e i , s o i l depth and type

s and eeology g ,

type and d e n s i t y o f f o r e s t r o a d s , movement and type of t r a n s p o r t mechanisms, and type of d e f o r e s t e d p l o t s , extending the d u r a t i o n of snow melting,

R1 - type of c u l t u r e , i t s r o o t system and the amount of biomass,

R2 - the r a t i o of middle-aged tree c l a s s e s , which have the h i g h e s t i n t e r c e p t i o n and t r a n s p i r a t i o n l o s s e s , P - the s t a t e of a g g r e g a t i o n of t h e p r e c i p i t a t i o n and i t s coincidence w i t h the season and s a t u r a t i o n p e r i o d s . The decrease i n r a t i o on t h e a r e a s u r f a c e by 30% i n dependence on o t h e r cond i t i o n s causes a n i n c r e a s e i n flood discharges of s i x times o r even more. The f a c t t h a t r a i n f o r e s t s are being destroyed by man a t the r a t e o f about llxl06ha every Rut

y e a r appears a l s o a s a warning i n t h i s connection. under c o n d i t i o n s of a n i n t e n s i v e f o r e s t e x p l o i t a t i o n and f o r e s t manage-

ment, the r a t i o of a f f o r e s t e d a r e a s is n o t the only d e c i s i v e f a c t o r of the water regime. This depends s u b s t a n t i a l l y on t h e depth of t h e s o i l , the age, s p e c i e s and c o n d i t i o n of the f o r e s t , and on c u l t i v a t i o n p r a c t i c e s (Tab. 4 . 7 ) . F u l l y a f f o r e s t e d a r e a s may have a n i n s u f f i c i e n t i n f l u e n c e t o balance the water regime as a consequence of wrong f o r e s t r y p r a c t i c e s which c o n c e n t r a t e the runoff.

To i n c r e a s e the t o t a l y e a r l y runoff from a f f o r e s t e d areas where spruce i s the main wood, without i n c r e a s i n g the flood d i s c h a r g e s , P e r i n a and Krecmer (1973)

2 84 TABLE

Class

4.7

Years

Clearing period 100 years decreased f o r e s t density

Clearing period 120 years f u l l f o r e s t density

Area

Area

Biomass Annual water concen- consumption t r a tion

CX) I. 11. 111.

IV V. VI. I

(&.ha-’)

0-20 20-40 40-60

20

1.0

20 20

0.8

60-80

20 20 0

0.8

80-100 1oc-120

T o t a l annual consmpti on

100

0.8

0.9 0.0

-

3 60 520

(XI

Biomass Annual water concen- consumption tration factor (2.ha-l)

10

1.0

180

20

1.0

560 800 720

730 670

20

1.0

20

1.0

560 0

20 10

1.0 1.0

2 60

2840

100

-

3300

600

The impact of f o r e s t density ( b i o m s s concentration measured i n t per hectare and compared with theoretical values of f u l l density according t o Schwabach (1890) on t o t a l annual runoff. Pine f o r e s t i n area with t o t a l annual r a i n f a l l 1200 mm. r e c m e n d the following biotechnical measures : ( a ) The c u l t i v a t i o n of f o r e s t s with a low stand density i n areas with low horizontal p r e c i p i t a t i o n i n order to decrease the interception losses. (b) To increase the r a t i o of younger tree classes and the r a t i o of clearing (openina) surfaces, and to l i m i t the r a t i o of the middle-aged t r e e classes, which have highest interception and transpiration losses, i . e . to shorten o r to extend the period of clearing i n areas with low horizontal p r e c i p i t a t i o n . ( c ) The change of tree species i n areas with low horizontal p r e c i p i t a t i o n , i .e. t o replace species with high interception and transpiration losses with species which have low interception and transpiration, to s u b s t i t u t e deciduous trees f o r spruces. (d) A considerable increase i n the r a t i o of the old spruce forests i n areas with high horizontal p r e c i p i t a t i o n and high stand density, and a decrease i n the r a t i o of the youngest growth and clearings destined f o r a f f o r e s t a t i o n . ( e ) The deforestation of s u i t a b l e areas i n accordance with the planned extension of the cultivated land, pastures , towns, industry and recreation development

.

The runoff c o e f f i c i e n t on a g r i c u l t u r a l lands depends on the cultivated species, t h e i r r o o t system: deep, shallow, i n t e r m i t t e n t , surface e t c . , t h e i r stage of

285 TABLE 4.8 Month

4

5

6

7

a

9

10

Grass land

6

13

37

li

12

16

16

Winter r y e

2

4

0

0

0

3

25 24

8

Spring wheat and b a r l e y Po t a toes

17 10

16

0

0

0

0

2

9

26

30

14

The impact of f i e l d crops on water accumulation i n s o i l (%) according to Rulavko (1971). Erowth and on the course of the p-owth depending on the s o i l thickness and type, the aRricultiira1 p r a c t i c e s and the s t a t e of aggregation of p r e c i p i t a t i o n . Measurements on a g r i c u l t u r a l s o i l s docment a considerable l o s s of water accumulat i o n i n comparison with s a s s l a n d , whose value depends on the season (Tab. 4.8). The change of pastures with a deep r o o t system i n t o a g r i c u l t u r a l f i e l d s m y r e s u l t i n a 30% i n c r e a s e i n the t o t a l yearly r u n o f f , when the r a i n f a l l occurs mainly i n the vepetation period. Also important a r e a g r i c u l t u r a l p r a c t i c e s : crop r o t a t i o n , weed removal, the depth and period of ploughing, a g r i c u l t u r a l c o m e r vation s e r v i c e s . h o w i t c h (1968)

shows t h a t deep ploughing can decrease the

y e a r l y runoff depending a l s o on the r a i n f a l d i s t r i b u t i o n by sme 25 t o 75%. Nevertheless compacting of t h e deeper soil l a y e r s by heavy t r a c t o r s and o t h e r a g r i c u l t u r a l machinery increases the s u r f a c e runoff. The i n t e n s i f i c a t i o n of a p r i c u l t u r a l production, r e s u l t i n g i n a n increased yield: - is either

accompanied by a growing evapotranspiration, enabled by an increa-

sed i n f i l t r a t i o n r a t e and higher moisture content i n the r o o t zone due t o a g r i c i i l t u r a l p r a c t i c e s loosening the s o i l l a y e r , thus l i m i t i n g the interflow and decreasing the recharpe of the groundwater, which r e s u l t s i n a decrease i n the t o t a l annual runoff and a decrease i n low discharges i n water courses, - o r caused by b e t t e r u t i l i z a t i o n of water by p l a n t s . I n t h i s second c a s e , the change ( i n c r e a s e o r even decrease) of the evapotransp i r a t i o n is less important, because the i n f i l t r a t i o n r a t e enables a n adequate recharge of groundwater and hemp has no s i g n i f i c a n t impact on the t o t a l annual runoff.

The impact of a g r i c u l t u r a l a c t i v i t i e s on the runoff c o e f f i c i e n t depends on four groups of f a c t o r s

c = c

-

f a ( L , A, R, P

runoff c o e f f i c i e n t

(4.13)

286 L

-

s t a b l e l o c a l f a c t o r s , e s p e c i a l l y the drainage a r e a shape and slope i , s o i l depth and typp d , geology g ,

A - a g r i c u l t i i r a l p r a c t i c e s and conservation services, e.g. contour or o t h e r

method of ploughinp, i t s depth and p e r i o d ,

R - p l a n t s p e c i e s , the depth and type of t h e i r r o o t system, the i n t e n s i t y of c u l t i v a t i o n , e.g. the y i e l d - b i o m s s r a t i o , P

-

the p r e c i p i t a t i o n aggregation, occurrence, i n t e n s i t y , d u r a t i o n and coincidence with p l a n t growth, s o i l processing and s a t u r a t i o n periods e t c .

TABLE 4.9

Area

Decrease i n t o t a l annual runoff

steppe ( c u l t i v a t e d land) F i e l d s and f o r e s t s Southern edpe of f o r e s t s

66 - 74 40 - 66 20 - 40

The decrease i n t o t a l annual runoff a s a r e s u l t of deep ploughinp of f i e l d s , expressed a s a percentage of o r i p i n a l v a l u e s , according to h o w i t c h (1965). The s e l e c t i o n of the p l a n t s p e c i e s and v a r i e t y a l s o depends on a g r i c u l t u r a l p r a c t i c e s and on the p o s s i b i l i t y of conservation s e r v i c e s , which have a b a s i c impact on the runoff c o e f f i c i e n t . An e v a l u a t i o n o f the i n f l u e n c e of the v e g e t a t i v e canopy on runoff leads to the following conclusions: ( a ) The consunption of water by p l a n t a t i o n s , f o r e s t s and o t h e r p l a n t n i t i e s depends m i n l y on the amount a v a i l a b l e i n the s o i l .

COIITTNJ-

(h) P l a n t ccmnunities of t h e same e c o l o g i c a l o r d e r use approximately equal volumes of water. Fast-prowing tree s p e c i e s do n o t u s e more water than slow m m i n p ones. (c)

Tne decrease i n the volume of t h e biomass i n c r e a s e s the t o t a l y e a r l y

runoff i n the same way a s the change of deep-rooted s p e c i e s i n t o s h a l l o w r o o t e d ones. ( d ) Tne a f f o r e s t a t i o n of prassland o r c u l t i v a t e d land decreases both s u r f a c e runoff and i n f i l t r a t i o n i n t o the groundwater. ( e ) The chanpes of the water regime a s a consequence of t h e f o r e s t and a g r i c u l t u r a l p r a c t i c e s a r e heteroEeneous and depend on s o i l , geomorphological and climatological conditions.

?he v e g e t a t i v e canopy a l s o has a s i g n i f i c a n t i n f l u e n c e on t h e a l t i t u d e of the moundwater t a b l e . A developed f o r e s t can cause i t to drop to sane ten meters

287

below the land s u r f a c e . Clearinp and thinning r e s u l t s i n a rise i n the groundwater t a b l e , depending on the geomorphological , hydrogeological, c l i m t o l o g i c a l and s o i l conditions. The deep r o o t system of the f o r e s t cover takes o f f the water from the lower s o i l l a y e r s . A f t e r c l e a r i n g a f o r e s t t h e groundwater table may r i s e over the land s u r f a c e . Such a r i s e , i n the case of low water q u a l i t y o r i f the water rises through s a l t y l a y e r s , a f f e c t s the q u a l i t y of the s o i l , inc r e a s i n g its s a l i n i t y . INFLIJENCE OF URBANIZATION AND IND~JSTRIALI7ATION

4.4

Urbanization and i n d u s t r i a l i z a t i o n influence a l l t h e f a c t o r s i n the equation

( 4 . l o ) , determining peak discharpes QmX, t o t a l runoff Q , minimum discharges -erosion i n t e n s i t y I,, groundwater regime G , water q u a l i t y q and the t o t a l r a i n f a l l P i . e . climatological f a c t o r s Xc, the f a c t o r of the vegetative canopy Xv, s o i l f a c t o r X,, morphological f a c t o r G, geological f a c t o r X,, and the water management f a c t o r X ,.

amin,

3

2

min Q r w 1

4

5

6h

Fig. 4.3. 'The increase i n flood discharges a s a consequence of urbanization: P - r a i n f a l l curve, Q - r i v e r discharge, W - detention s t o r a g e and water accumulation i n the s o i l l a y e r , C, soundwater accumulation, A accumulation i n the seweraEe network. P = Wo + Go = W, + Ax + G,. IMXF'X maxPo; tp. >ho;

-

-

minQx

< rninQo; (& < Go;

tqx

< tqo;

ql0...

q,

<

qlx

.... .qnx

(pollution).

288 The b a s i c hydrological consequences of iirbanization and i n d u s t r i a l i z a t i o n a r e a s follows: ( a ) a r i s e i n water requirements, whose t o t a l m y exceed the capacity of the water resources of the a r e a i n question, n e c e s s i t a t i n g the diversion of water from upstream sources o r from e x t e r n a l r i v e r basins (Fig. 4.11) (b) a decrease i n i n f i l t r a t i o n on account of the built-up a r e a s ( c ) a f a l l i n the groundwater t a b l e and a decrease i n the n a t u r a l gmundwaLer outflow (d) a concentration of and a c c e l e r a t i o n i n the s u r f a c e runoff a s a r e s u l t of the change i n the n a t u r a l system of drainage, and a concentration of flow i n the sewerage sys tern ( e ) a r i s e i n peak discharges, and an increase i n t h e yearly t o t a l of

SUI

f a c e runoff ( f ) a rise i n erosion on land sLripped by c o n s t r u c t i o n a c t i v i t i e s (Tab.4.6) (g)

increased p o l l u t i o n of streams, a l s o caused by waste d i s p o s a l , which

exceeds the capacity of the n a t u r a l s e l f - p u r i f i c a t i o n processes and causes a steady increase i n groundwater p o l l u t i o n (h) a decrease i n the n a t u r a l flow capacity of r i v e r beds due to the urban i z a t i o n of t h e flood p l a i n and increased sediment t r a n s p o r t , thus exacerbating flood damage ( i ) a decrease i n evapotranspiration w i n g t o t h e r e s t r i c t i o n of bare s o i l and vegetation-covered

surfaces by built-up a r e a s , and an increase i n evapora-

t i o n due t o i n d u s t r i a l production ( j j h e a t production and a rise i n temperature i n the urbanized area ( k ) change of the albedo, owing to the change of the q u a l i t y of the landscape s u r f a c e (1) an increased p r o b a b i l i t y of r a i n f a l l occurrence a s a r e s u l t of the increased number' of condensation n u c l e i , owing to t h e a i r p o l l u t i o n (m) a change i n ecosystems a s a consequence of t h e previous changes.

'he increase i n s u r f a c e runoff r e s u l t s not only from the decrease i n i n f i l t r a t i o n , e s p e c i a l l y through the reduced surface permeability of t h e built-up, c m n i c a t i o n and o t h e r s u r f a c e s , but a l s o from the d e c l i n e i n surface roughness. This is caused by the replacement of the o r i g i n a l vegetative canopy by the smooth m a t e r i a l s of buildings and communication l i n e s . ' h e topography of t h e area i n question a l s o undergoes d r a s t i c changes, simplifying the complicated conditions of the o r i g i n a l unconcentrated flow by more s t r a i g h t and s h o r t ways. Tne rise i n s l o p e increases the v e l o c i t y of the overland flow and leads t o a higher concent r a t i o n of runoff. Land grading and the i n c r e a s e i n v e l o c i t y reduce the detention storage. The underground stora,qe has been reduced by the decline i n the i n f i l t r a t i o n

rate. Because t h e s u r f a c e and undereround s t o r a g e are d r a s t i c a l l y decreased, t h i s r e s u l t s i n an i n c r e a s e i n the frequency of flood occurrence and an increase

2 89 i n the v a l u e s of r e l e v a n t peak d i s ch ar g es. In such a way, even r a i n f a l l s occurring d u r i n g dry periods may cause high peak discharges and n o t s u f f i c i e n t l y supplement the groundwater s t o r ag e. Urbanization and i n d u s t r i a l i z a t i o n i n c re a se the t o t a l ye a rly runoff, proport i o n a l l y w i t h t h e uinpenneabi li ty of t h e land surfa c e and w ith the concentration of the outflow by t h e sewerage system. According to Costin and Dooge (1972), peak dischar,pes i n cr eas e f i v e to ten times with a corresponding reduction i n t h e i r d u r a t i o n , dependinp on t h e frequencv of t h e i r occurrence. The runoff coeff i c i e n t a l s o rises t h r ee t o f o u r t i m e s . The average inc re a se i n the t o t a l nino f f (5-:5%) i s thus comparatively lower than the r i s e i n peak discharges (Fig. (4.7). The development of changes i n the hydrologic cycle depends on the expansion of t h e urbanized a r e a , and on i t s development phase, interconnected with the a g r i c u l t u r a l development of t h e ad j o i n i n g region (Tab. 4.10). l.!rbanization and i n d u s t r i a l i z a t i o n g r e a t l y influe nc e the water regime a s well a s the values of l o w d i s ch ar g es . The reduced i n f i l t r a t i o n leads t o a f a l l i n the proundwater t a b l e and t o a decrease i n the volume of t h e groundwater re se rve , occasionaIly causing t e r r a i n s e t t l e m e n t s . Low discharges i n r i v e r courses a r e decreased by water withdrawals and by t h e reduced water recharge from groundwater r e so u r ces . W i l d i n g and t h e r e s u l t a n t o v er s h ad ming of plots decreases the a i r motion and hence t h e evaporation r a t e . Concerning the t o t a l y e a r l y e va potra nspira tion,

i t may be e i t h e r decreased, i n a r e a s with low evaporation l o s s e s , o r increased, e s p e c i a l l y i n i n d u s t r i a l a r e a s by evaporation from cooling sys terns and i n tropic a l and s u b t r o p i c a l regions by i n t e n s i v e i r r i g a t i o n of municipal parks and pardens. The development of vast i n d u s t r i a l i z e d and urbanized a re a s a l s o a f f e c t s the t o t a l y e a r l y r a i n f a l l . Costin and Dooge (1973) e stim a te i t s increase a t some 10%. This r i s e i s a consequence of the hi,pher i n t e n s i t y of a i r mass motion above the covered a r e a , i t s increased temperature, caused e s p e c i a l l y by he a t product i o n , a i r p o l l u t i o n and sometimes by t h e increased evaporation, e s p e c i a l l y from i n d u s t r i a l production p r o ces s es . The i n c r e a s e i n the t o t a l ye a rly r a i n f a l l has been proven s t a t i s t i c a l l y , b u t n o t the rise of m x h m values of p r e c i p i t a t i o n .

The i n c r e a s e i n t h e frequency of storm occurrence has a l s o been recorded. The increased r a i n f a l l co n t r i b u t es t o t h e frequency of flood occurrence and t h e i r duration. Tne most th r eat en i n g e f f e c t of u r b an i za tion and i n d u s t r i a l i z a t i o n is the pmduction of h e a t energy, which is i n cr eas inE by some 5% ye a rly on a globa l s c a l e . Tnis advancement means an increment of 500% i n 35 ye a rs. I n the ye a r 2000 m n y huge areas w i t h a s u r f a c e of some 103 t o lo5 sq. km w i l l 'emerge, where t h e i r am a r t i f i c i a l h e a t production w i l l exceed the acceptance of s o l a r energy.

290 TABLE 4.1C

Changes i n land o r water use

Hydrological e f f e c t

~~

Clearing, removal of

Decrease i n t r a n s p i r a t i o n , increase i n evaporation.

vegetation

Increase i n overland flow, flood frequency arid peak floods. Increased s o i l erosion and sedimentation of streams. Raised groundwater t a b l e . Change i n albedo.

Plou ph i n p

Change i n s o i l s t r u c t u r e . Increased i n f i l t r a t i o n and

Larpe-scale produc-

Liquidation of small streams and dry beds, increase

t i o n , rnechaniza t i o n

i n overland flow and erosion r a t e , increase i n

evaporation. Escape of carbon dioxide.

sedimentation of streams

~

environmental p o l l u t i o n .

Stream clogrring. Rise i n groundwater t a b l e . Increase i n i n evapotranspiration r a t e . Cooling of s o i l surface and a i r a i r temperature. Change i n albedo. Chanee i n s o i l s t r u c t u r e and q u a l i t y (increased s a l i n i t y ) . Dra i n a ge

Drop i n groundwater t a b l e . Decrease i n evapotransp i r a t i o n warming of a r e a , change i n albedo. Increased i n f i l t r a t i o n . Change of s o i l s t r u c t u r e and q u a l i t y (decrease i n s a l i n i t y ) . Impact on the q u a l i t y of the surface water.

well e r e c t i o n

Decrease i n eroundwa t e r t a b l e .

Sewage d i s p o s a l

Local increase i n s o i l moisture. Increasing p o l l u t i o n

of w e l l s and streams. h s s construction:

Increased erosion and sedimentation of streams.

Land grading and

Liquidation of small streams - flooding of land

excavations

during high r a i n f a l l .

Comnunica t i o n and

Decrease i n i n f i l t r a t i o n r a t e , drop i n groundwater

s tom drainage

t a b l e and land surface. Increase i n surface runoff

s y s tern cons truc t i o n

and flood occurrence. Lower base flow. Increased p o l l u t i o n of streams. Change i n albedo.

Construction of t h e

Increased water wastage. Rise of the groundwater

mass water supply

t a b l e around wells of the previous

and d i s t r i b u t i o n

supply, lowered

sys tern

water withdrawal. Decrease i n runoff a t p o i n t of with-

l o c a l water

water t a b l e i n l o c a t i o n of t h e mass

drawal and downstream. Problems o f waste water disposal

291

TABLE 4.10 (Cont'd) Changes i n land o r water use

Hydrological e f f e c t

Construction o f

Iand d r a i n a g e , decrease i n groundwater recharge.

sewage system

Increased p o l l u t i o n o f streams, e s p e c i a l l y during low discharges and when system a l s o used f o r t h e d i s p o s a l of i n d u s t r i a l waste water. Degradation of water f o r downstream u s e r s , loss o f a q u a t i c l i f e .

Waste water treatmerit

Decrease i n p o l l u t i o n of streams, improvement of

p l a n t construction

water q u a l i t y downstream, improved conditions f o r aquatic l i f e .

Late urban s t a g e

Room i n water requirements. Decrease i n water q u a l i t y .

L o n r d i s tance water

Increased ninoff i n a f f e c t e d streams. Increased

transfer

evaporation from the catchment.

Deep l a r g e c a p a c i t y

Overdraft r e s u l t s i n land subsidence.

wells

C h e c k l i s t of impact of u r b a n i z a t i o n a c t i v i t i e s and of interconnected land and water u s e on t h e hydrologic s c a l e and water a v a i l a b i l i t i e s . This w i l l l e a d t o a n unproportional i n c r e a s e i n t h e temperature over these s c a t t e r e d a r e a s and a l s o i n f l u e n c e t h e g l o b a l climate. The rise i n temperature i n t h e atmosphere w i l l i n c r e a s e evaporation from t h e oceans: thus t h e hydrologic c y c l e w i l l be more i n t e n s e . There w i l l be weakened e q u a t o r t o - p o l e temperature g r a d i e n t , so t h e general atmospheric c i r c u l a t i o n w i l l b e less vigorous, r e s u l t i n g i n more p r e c i p i t a t i o n i n t h e region of t h e p r e s e n t s u b t r o p i c a l d e s e r t s . The g r e a t e s t change may occur i n p o l a r r e g i o n s . The a r c t i c Ocean i c e pack, p r e s e n t l y h i g h l y r e f l e c t i n g , can, a f t e r p o l l u t i o n of i t s s u r f a c e , absorb more s o l a r e n e r a . I t may happen t h a t t h e wamiing e f f e c t described above might remove t h i s i c e pack completely. The r e l a t i v e l y f r e s h water from i t s melting has a lower d e n s i t y than nonnal sea water. Wave a c t i o n and water c u r r e n t s can mix i t with sea water, d e c r e a s i n g t h e p r o b a b i l i t y t h a t t h i s water will f r e e z e again. This w i l l l e a d to a f u r t h e r i n t e n s i f i c a t i o n o f evaporation and p r e c i p i t a t i o n . Conceining t h e r e l a t i v e l y l a r g e r i c e s h e e t s o f t h e A n t a r c t i c and Greenland, any s m l l change i n t h e i r i m e n s e volume would a f f e c t t h e mean sea l e v e l . Their m e l t i n e has been one of the reasons f o r t h e r i s e i n mean sea l e v e l of about

0.2 m from the heginning of t h i s century. A complcte melting would i n c r e a s e t h e

292

Fig. 4.10. Schematic representation of the impact of human a c t i v i t i e s on erosion, water q u a l i t y ar,d s e l e c t e d hydrological processes. mean sea l e v e l by about 70 m. B u t such an event would appear to be very unlikely durine the next 10 to 100 thousand years. The r i s e i n the average global temper a t u r e m y n o t even decrease t h e i r volume because of the increased r a i n and snowfall, which w i l l supplement t h e i r ice pack. The changes i n the energy balance a r e l i k e l y to increase the temperature i n polar regions by about + 10°C i n t h e year 2050, a l s o extending the local veget a t i o n period: a t the l a t i t u d e of 50' by about 15 days, a t 70' 30 days on average, depending on p r e c i p i t a t i o n occurrence. 4.5

by about some

CHANGES IN WATER QUALITY The physical, chemical and b i o l o g i c a l c h a r a c t e r i s t i c s of water a r e formed n o t

only during i t s penetration through the atmosphere, s o i l and rock environment, but a l s o during i t s c o n t a c t with the v e g e t a t i v e canopy,. F o r e s t s and o t h e r cultures therefore have an important e f f e c t on the b a c t e r i o l o g i c a l and chemical q u a l i t y of w a t e r , and on i t s t u r b i d i t y . This q u a l i t y a l s o depends on the p l a n t species, the composition of ecosystems, t h e s t a g e of growth and season; a l s o important are t h e impact of p o l l e n and t h e changes caused by harvesting, ploughing e t c . Changes i n t h e ecosystem of t h e v e g e t a t i v e canopy, i . e . changes i n t h e plant species o r c u l t i v a t i o n p r a c t i c e s , r e s u l t i n a change of water q u a l i t y .

293 Waters from a f f o r e s t e d areas a r e g e n e r a l l y of good quality,which a l s o depends on t h e h e t e r o g e n e i t y of t h e ecosys terns: the replacement of f o r e s t p o ~ y c u l t u r e s by monocultures leads t o a n i n c r e a s e i n a c i d i t y . Rut i n a r e a s with high r a i n f a l l decaying v e g e t a t i o n causes water contamination, d e p l e t i n g the d i s s o l v e d oxygen and i n c r e a s i n g t h e a c i d i t y e t c .

,

e s p e c i a l l y i n t r o p i c a l and s u b t r o p i c a l condi-

t i o n s of high temperatures. Water from a f f o r e s t e d catchments can a l s o become b a c t e r i o l o g i c a l l y contaminated by w i l d l i f e , and p a r t i c u l a r l y by b i r d s .

'he p o l l u t i o n of water resoiirces is a consequence of - n a t u r a l processes: e r o s i o n , v o l c a n i c a c t i v i t i e s and b i o l o g i c a l processes, and by human a c t i v i t i e s , e s p e c i a l l y by - incre2sing e r o s i o n owing t o d e f o r e s t a t i o n , wrong c u l t i v a t i o n p r a c t i c e s and urbanization, - washinp of a g r o c h m i c a l s from a g r i c u l t u r a l and s i l v i c u l t u r a l production ( f e r t i l i z e r s and pes t i c i d e d ) , - a c c i d e n t s during the t r a n s p o r t of f u e l and o t h e r chemicals,

- d i s p o s a l of gaseous, l i q u i d and s o l i d wastes from i n d u s t r y , t h e m 1 and nuclear power p m p r a t i o n , a g r i c r i l t u r ~ , dwelling a r e a s e t c . - subsequent leaching of wastes deposited on the s u r f a c e , under the grcund o r i n water, - i n f i l t r a t i o n of p o l l u t e d w a t e r from or t o groundwater resources e t c . The r a t i o of these processes t o t h e t o t a l water p o l l u t i o n depends on the n a t i i r a l c o n d i t i o n s , the development s t a g e and r e l e v a n t p r a c t i c e s . Erosion forms t h e p r e v a i l i w p a r t (90'7 o r even more) of p o l l u t i o n i n c o u n t r i e s with t r a d i t i o n a l i n t e n s i v e a g r i c u l t u r e . The washine of agrochemicals may c o n t r i b u t e by more than

50% t o the t o t a l p o l l u t i o n of s u r f a c e and groundwater r e s o u r c e s , even i n h i & l y i n d u s t r i a l i z e d c o u n t r i e s . llunicipal p o l l u t i o n , due t o i t s p a r t l y organic o r i g i n ,

i s l e s s harmful than t h e p o l l u t i o n from i n d u s t r y and t h e s t o c k i n g of chemicals. Hazardous a c c i d e n t s during the t r a n s p o r t a t i o n and s t o c k i n g of f u e l and o t h e r chemicals can be p a r t i c u l a r l y dangerous, owing t o t h e i r q u a n t i t i e s o r chemical properties,

as w e l l a s a c c i d e q t s i n nuclear power p l a n t s .

The term p o l l u t i o n r e f e r s t o u n d e s i r a b l e changes i n t h e p h y s i c a l , chemical and b i o l o g i c a l p r o p e r t i e s of a i r , s u r f a c e w a t e r , groundwater and the n a t u r a l environment which p r e j u d i c e the l i v i n g conditions of h m a n beings and d e s i r a b l e b i o l o g i c a l s p e c i e s and imperil these conditions i n f u t u r e , as w e l l a s lead t o a d e t e r i o r a t i o n i n n a t u r a l resources and neEatively a f f e c t production processes, a e s t h e t i c o r c u l t u r a l values and endanger them i n f u t u r e . The atmosphere and the q u a l i t y of p r e c i p i t a t i o n has been p o l l u t e d by carbon dioxide C02, n i t r o u s oxide N 2 0 , s u l p h u r dioxide SO2, o t h e r gases, s u l p h a t e s , chlorof luoromethanes and a e r o s o l s produced by i n d u s t r y , thermic power generation, t r a n s p o r t , space h e a t i n g , slash-and-bum and o t h e r a g r i c u l t u r a l p r a c t i c e s e t c . Mithin t h e framework of t h e hydrologic cycle p o l l u t i o n passes from a i r to water and f r m one e l e n e n t of t h e environment t o another.

2 94

. r

LEAD IN

UPPER ATHMOSPHERIC LAYERS

PETROL

25 O/o c

Evaporation

.

4

Pb

ROAD

40% Combustion r

ENVIRONMENT

WATER COURSES

Fip. 4.11. P e n e t r a t i o n of lead Pb, produced by combustion engines used i n p u b l i c t r a n s p o r t , i n t o the hydrologic c y c l e accorddng t o Fishbein (1976). P o l l u t a n t s can be categorized as: ( a ) harmless matter, which can e a s i l y be removed from water through f i l t r a t i o n and o t h e r s e l f - p u r i f i c a t i o n p r o c e s s e s , ( b ) t o x i c matter and m a t t e r causing s e n s o r i a l ( o r g a n o l e p t i c ) problems f o r organisms (Fig. 4.11). (c)

matter i n f l u e n c i n g the oxygen demand of w a t e r ,

(d)

anorganic p o l l u t a n t s , d i s s o l v e d o r i n s o l u b l e , i n c r e a s i n g t h e s a l i n i t y

of water. Toxic matter can cause problems o r breakdowns i n the various b i o l o p i c n l f m c t i o n s of an organism and i t s d i v e r s e organs (e.g. cancerogens), a s w e l l a s f u r t h e r p h y s i o l o g i c a l and psychical and e v o l u t i o n a l changes (mutagens and teratogens) depending on the c o n c e n t r a t i o n and accepted q u a n t i t y of t h i s matter, the i n f l u e n c e of o t h e r m a t t e r and on t h e age and h e a l t h s t a g e of the organism. These problems may occur n o t only s h o r t l y a f t e r the c o n t a c t , b u t a l s o i n t h e long term over a period exceeding even 40 years (Fig. 4 . 1 2 ) . Research i n t o t h e impact of d i f f e r e n t kinds of t o x i c m t t e r and, e s p e c i a l l y t h e i r s y n e r p e t i c e f f e c t , is s t i l l i n a n e a r l y stare. This e f f e c t can t h e r e f o r e be n e i t h e r q u a l i t a t i v e l y nor q u a n t i t a t i v e l y e s t a b l i s h e d . The problem i s very ccmplicated, e s p e c i a l l y because of the varyinp r e s i s t a n c e of the same organisms under s i m i l a r c o n d i t i o n s , because of the e f f e c t of o t h e r f a c t o r s , and because of

295

HAS04

ASH,

CH, ASH,

(CHJ ASH

-H

-H

Fig. 4.12. Changes i n a r s e n a t e compounds d u r i n e the course of t h e hydrologic cycle. the changes i n these matters during t h e i r passaae through the environment. Some chemicals a r e c h g l i c a l l y s t a b l e and pass through various b i o l o g i c a l and physical processes w i t h o u t change ( e . p . DDT

-

F i g . 4. i 3 ) , endangerinp e s p e c i a l l y

h i g h e r organisms by t h e i r accumulation, i . e . remaining i n t h e i r organs i n a s i i h s t n n t i n l l v c o n c m t r a t c d form i n canparison with t h e i r concentrations i n lmpr clarients in the hiolog,lcal chain.

Fig. 4.13. P e n e t r a t i o n of thp i n s e c t i c i d e DDT i n t o t h e hydrolopic c y c l e and i t c accumiulation i n h i g h e r organized organic m a t t e r accordinp to Woodwell (1965). Conccntration i s hatched.

296 The harmfulness o r harmlessness of r e l e v a n t p o l l u t a n t s depend on many f a c t o r s such a s t h e i r mutual e f f e c t , t h e i r d u r a t i o n , the p r e v a i l i n g h e a l t h s t a n d a r d s , i n d i v i d u a l r e s i s t a n c e e t c . The genera1 l e v e l of knowledge about these f a c t o r s is

s t i l l u n s a t i s f a c t o r y . I t i s e.p. presumed t h a t 50 t o 90% of the cases of cancer a r e a consequence of the s y n e r g e t i c i n f l u e n c e of cancerogens. The h i g h e s t c o n c e n t r a t i o n of t h e m t t e r supposed t o have a n undesirable e f f e c t

is the s a n i t a r y admissible concentration. These concentrations can b e d i s t i n g u ished f o r ( a ) i n d i r e c t l y harmful consequences, ( b ) s e n s o r i a l ( o r m n o l e p t i c ) consequences, ( c ) t o x i c consequences. TABLE 4.11 Ga t e g o r i e s of waste water

Comnents

1.

Intensively acid or i n tens i v e l y a l k a 1i n e

Contain a c i d s o r bases i n high concentrations.

2.

With high degree of minera 1i z a t i o n

Not s u f f i c i e n t l y s u i t a b l e f o r f u r t h e r u t i l i zation i n industry o r agriculture.

3.

With high content of suspended m a t t e r

Produce secondary p o l l u t i o n by i t s b i o l o g i c a l decay. I n j u r i o u s f o r f i s h e s .

~~

~~

~

4 . With nlatter i n f l u e n c i n g

Tenzids, o i l products, grease e t c .

t h e oxygen i n p u t

5.

With high c o n t e n t of b i o l o g i c a l l y degradable 'matter o r m a t t e r consuming oxygen chemically

D m e s t i c sewage. The change of a e r o b i c processes t o anaerobic ones. The lack of oxygen causes p e r i s h i n g of f i s h e s .

6.

With roa tter k f luencing the s e n s o r i a l p r o p e r t i e s

Chlorphenols, o i l products, s o l v e n t s etc.

7.

With t o x i c matter

Heavy metals, p e s t i c i d e s radioactive matter.

, n i trogenic

and ~

8. With pathogenic germs

Water from s a n i t a r y s e r v i c e s , t a n n e r i e s e t c .

9. With predominant n i t r o g e n

F e r t i l i z e r s , d e t e r g e n t s . Eutrophic influence.

and phosphorus compounds

10. Warn waters

Decrease i n oxygen c o n t e n t , i n c r e a s e i n metabolism of water fauna and its oxygen requirements, r e s u l t i n g i n a decrease i n the s e l f - p u r i f i c a t i o n c a p a c i t y , providing the a e r a t i o n is not predominant.

Categories of waste water depending on t h e predominant type of p o l l u t i o n accord i n g t o P i t t e r (1972).

297 Waste waters can be categorized on the b a s i s of t h e i r main cmponents, which a l s o c h a r a c t e r i z e t h e i r p r e v a i l i n g harmful e f f e c t s (Tab. 4.11). P o l l u t i o n direct l y caused by waste disposal is primary p o l l u t i o n . I f i t does not exterminate a l l organic l i f e , a development of some undesirable organisms, namely d e t r u e n t s , occurs. The mass decay of these organisms causes secondary p o l l u t i o n . Human a c t i v i t i e s draw new, mostly harmful components i n t o n a t u r a l cycles and thus influence the n a t u r a l c i r c u l a t i o n r a t e of t h e main biogeoelements. In such a way t h e volume of the nitrogen c i r c u l a t i o n i s increased, e s p e c i a l l y by ( a ) gazeous emissions and a e r o s o l s from burning and o t h e r chemical processes, (b) l i q u i d wastes from i n d u s t r i a l estates, ( c ) the use of n i t r a t e f e r t i l i z e r s , a c c e l e r a t i n g the b i o l o g i c a l production of n i t r o u s oxide. N i t r i d e s a r e quickly soluble and t h e r e f o r e mobile, i . e . i t i s d i f f i c u l t to keep them i n the s o i l and very easy t o wash them away. Losses by washing reach some 20 - 40% on average. Only a m n i a s a l t s can be bound i n the s o i l , but they a r e n o t s t a b l e , changing i n t o n i t r i d e s i n s o i l . A d i r e c t r e l a t i o n e x i s t s , t h e r e f o r e , between the content of nitrogen i n su1' face waters and i n the i n t e n s i t y of f e r t i l i z i n g . A s u b s t a n t i a l p a r t of such contamination comes from t h e groundwater, p o l l u t e d by p e r c o l a t i o n n i t r i d e s from fertilized fields. Five hundred m i l l i o n tons of n i t r o u s oxide N20 e n t e r s the atmosphere annually, mainly by b i o l o g i c a l decay and d e n i t r i f i c a t i o n processes taking place i n s o i l s and oceans. H m n a c t i v i t i e s p r e s e n t l y account f o r some 10%of t h i s f i g u r e . The r a t e of t h e d e n i t r i f i c a t i o n process by s o i l organisms depends on t h e s o i l ' s a c i d i t y . The r a t i o of N2 t o N 0 produced by s o i l b a c t e r i a increases from 0.05

2

t o 0.2 i n a c i d s o i l . The r a t e of nitrogen and n i t r o u s oxide production depends, t h e r e f o r e , on t h e production of sulphur dioxide and s u l p h a t e s , i . e . the i n t e r r e l a tionships of t h e biogeoelements ' c i r c u l a t i o n a r e complex. Human a c t i v i t i e s a l s o change t h e unbalanced c i r c u l a t i o n of phosphorus, namely by means of the waste water d i s p o s a l and by f e r t i l i z e r wash from a g r i c u l t u r a l a r e a s . The compounds of phosphorus a r e d i f f i c u l t to dissolve. They a r e fixed a s ferrum phosphates i n a c i d s o i l s and a s calcium phosphates i n a l k a l i n e s o i l s . Nevertheless, e s p e c i a l l y through the long-term a p p l i c a t i o n of phosphates on l i g h t or organic s o i l s with a low absorption capacity, they escape and p o l l u t e the

.

groundwater The i n c r e a s e i n the carbon oxide CO and carbon dioxide CO concentration re2 s u l t s mainly from ( a ) a g r i c u l t u r a l production processes, e s p e c i a l l y a s a consequence of plough inE, (b) the continued r i s e i n t h e burning of f o s s i l f u e l s . Six b i l l i o n tons of carbon oxide e n t e r s the a t m s p h e r e per annum through in-

298 TABLE 4.12 P o t e n t i a l impact (diseases) Pulmonary

Beryllium Be, Cadmium Cd, Chromium C r , Selenium Se, Manganese Mn

Liver

Selenium Se, Nickel Mi: carbon chloride CC14, chlorinated phenols

Kidney

T i thium L i , Lead Pb, S tronciim S r , Selenium Se, Nickel Ni, Cadmium Cd e s p e c i a l l y cadmium s u l p h a t e CdS04, e thylenglyco 1

Nervous system

Mercury Hg, Stroncium S r , Manganese Mn, Lead Pb, Calcium Ca, Cadmium Cd

Me taheanioglobinanemia

n i t r i t e s and n i t r a tes

Fluorisis

Fluorides

Canceerogens

tar, a s p h a l t and combus t i o n gases, Chromium C r , Nickel N i , Beryllium Be, n i t r i d e s and n i t r a t e s , nitrosamins, polyc h l o r i n a t e d biphenyles, petroleum, t r i a z i n , polyuretan, polyvinylchloride , benzene, polynuclear arcmatic. hydrocarbons, chlorophom, bromophoim, asbes t , p e s t i c i d e s endrine, d i e l d r i n e , chlordane, endring, DDT e t c . )

-

Selected t o x i c m a t t e r , occuring e s p e c i a l l y i n waste water and t h e i r possible impact on human h e a l t h .

complete combustion i n conditions of a r e s t r i c t e d access of oxygen

-

the share

of combustion engines i n t r a n s p o r t is more than 75%. The carbon dioxide i n the atmosphere has r i s e n from 0.028% i n 1860 to the present 0.033% and m y double by the next mid-century. Its content i n the atmosphere increases e s p e c i a l l y a s a r e s u l t of the change of a f f o r e s t e d areas i n t o a g r i c u l t u r a l land. According t o Wilson (1975) the percentage of t h e carbon dioxide i n t h e atmosphere has r i s e n by about 10% i n the period 1860-90 by ploughing v a s t a r e a s i n America, South A f r i c a , A u s t r a l i a and h s t e m Europe. The burning of f o s s i l f u e l s increases t h i s content by about 0.0001% y e a r l y , but the combustion of a l l f u e l s a v a i l a b l e would increase t h i s f i g u r e almost twenty times. Obvious a d d i t i o n s t o the atmosphere, produced by a combination of burning and the photochemical r e a c t i o n s i n the presence of u l t r a v i o l e t r a d i a t i o n , a r e aeros o l s , a combination of s o o t p a r t i c l e s , sulphur dioxide SO2, sulphates and unburned hydrocarbons. An important influence is had h e r e by sulphur dioxide SO2 and sulphur t r i o x i d e SOg, which

occure e s p e c i a l l y a s a product of low q u a l i t y

299

flip1 burninp. The n a t u r a l vulcanic production of sulphur dioxide is some 140 m i l . ton ad

R

y e a r l y , while power g e n e r a t i o n , space h e a t i n e and o t h e r human a c t i v i t i e s

sane 50%more t o t h i s f i g u r e .

A i r p o l l u t i o n i n f l u e n c e s water c i r c u l a t i o n i n a n important way, because (a)

carbon d i o x i d e , chlorofluorornethanes, n i t r o u s oxide and o t h e r i n f r a r e d

absorbing gases absorb t e r r e s t r i a l i n f r a r e d r a d i a t i o n i n several i n f r a r e d bands, thereby warminp the Farth ' s s u r f a c e , ( h ) a e r o s o l p a r t i c l e s over a dark s u r f a c e such as oceans i n c r e a s e the n e t albedo, b u t lower the albedo over the l a n d , althouph t h e i r o v e r a l l i n f l u e n c e is n o t known y e t , ( c ) a e r o s o l s produced by burninp and i n d u s t r y a c t a s good condensation and f r e e z i n p n u c l e i , thus i n c r e a s i n g the p r o b a b i l i t y of r a i n f a l l occurrence. The p o l l u t i o n frcm the a i r e n t e r s t h e s o i l and water e s p e c i a l l y through (a)

washing-out of gases and a e r o s o l s from the atmosphere by r a i n f a l l ,

(b)

a b s o r p t i o n o f gases by the s o i l , v e g e t a t i o n and water,

( c ) s e t t l i n g o f s o l i d p a r t i c l e s on the v e g e t a t i o n and s o i l and i n the water. One of t h e obvious r e s u l t s i s a n i n c r e a s e i n the a c i d i t y of r a i n f a l l and s u r f a c e waters including n a t u r a l l a k e s . The course of a i r p o l l u t i o n i s uneven, and t h a t of the a i r motion too, s o the a c i d i t y of r a i n f a l l a t one p l a c e fluctua t e s i n time. R u t t h e o v e r a l l r e s u l t on the s u r f a c e water q u a l i t y is a r i s e i n

i t s a c i d i t y , caused namely hy (a)

the inflow of a c i d r a i n f a l l ,

(b)

the leaching of a c i d geological l a y e r s ,

(c)

the inflow of a c i d waste w a t e r s ,

( d ) the supply of s a l t s from the s e a water through the atmosphere. The increased a c i d i t y of s u r f a c e water causes changes i n t h e r e l e v a n t ecosystems, manifested f i r s t by a reduction i n t h e i r d i v e r s i t y . The decrease of the

pH f a c t o r below 5.5 is a l s o c r i t i c a l f o r most f i s h s p e c i e s , decreasing the over-

a l l b i o l o g i c a l a c t i v i t y and changing t h e n u t r i t i o n chains. A s i m i l a r influence occurs on s o i l s . Rut t h e r i s e i n t h e s o i l a c i d i t y i s o f t e n a r t i f i c i a l l y neutral i z e d by liming i n o r d e r t o i n c r e a s e y i e l d . On the whole, t h e e f f e c t s of p o l l u t i o n a r e remarkably n e g a t i v e (Tab. 4.11). The r e l e v a n t i n t e r r e l a t i o n s h i p s are complex, and n o t y e t f u l l y qiiantified. Tne r e s u l t of anthropogenetic influences on t h e c l i m a t e

, environmental

q u a l i t y and

the hydrologic c y c l e , a l s o i n f l u e n c i n g l i v i n g conditions and human l i f e , cannot y e t be s u f f i c i e n t l y q u a n t i f i e d .

4.6

ENVIRONMENTAL IMPACTS OF WATER DEVEU)PM!SNT PROJECTS The e x p l o i t a t i o n of water resources is i n e v i t a b l y accompanied by a disturbance

of the n a t u r a l balance. The e x t e n t of the i n f l u e n c e of these p r o j e c t s on the environment depends on the e x t e n t o f t h e changes i n t h e water repime i n the a r e a concerned (Tab. 4 . 1 3 ) .

3 00 TABLE 4.13 Environmental f a c t o r s (external)

sys tern f a c t o r s ( i n t e r n a l )

Stable

Stable

Variable

Variable abiotic

climate peopraphical p o s i t i o n a1 t i tude morphology geo1ogy s o i l factors n a t u r a l water q u a l i t y

wea ther discharges ice phmomena human activities

project hydrological size meteorological purpose rnicroclima toopera tior? l o g i c a l o t h e r physical chemi ca1 propress of the p r o j e c t

biotic ecosys tms social sys tems

Categorization of b a s i c f a c t o r s wnich determine the impact of water development on the environmmt and on human s o c i e t y . The i d e n t i f i c a t i o n of environmental impacts should be an e a r l y a c t i v i t y i n the planning porcess. Environmental s t u d i e s a r e needed t o r e s t r i c t undesirable e f f e c t s and i d e n t i f y appropriate mitigation measures. An assessment' of the environmental impacts requires - a general knowledge of the impacts of s i m i l a r water development pro'jects under s i m i l a r gemorphological and climatological conditions, - a systematic approach based on the iise of c h e c k l i s t s , i n t e r s e c t i o n m t r i c e s and networks,

-

a q u a n t i t a t i v e approach based on mss balance and environmental d i l u t i o n

calculations ,

-

the u s e of m thema t i c a l models f o r mu1 t i p l e environmental f a c t o r s , case s t u d i e s and p i l o t p r o j e c t s . The purposes of constructing water development p r o j e c t s can be c l a s s i f i e d a s

(a) r e g u l a t i n g - provision of water f o r d i f f e r e n t purposes and safeguarding of i t s supply, a l s o i n periods of low n a t u r a l discharges and high water requirements, by accumulating water i n s u r f a c e and underground r e s e r v o i r s diiring p e r iods of s u r p l u s , or by its conveyance. (b) c o n t r o l - reduction of high discharges and high water t a b l e s , runoff r e t a r d a t i o n , s o i l conservation, reduction of e r o s i o n , c o n t r o l of s i l t load i n

streams by conservation s t o r a g e , r i v e r t r a i n i n g , water conveyance e t c . (c) d i s t r i b u t i o n and drainage - water supply f o r municipal, i n d i i s t r i a l and a g r i c u l t u r a l use, sewage c o l l e c t i o n and removal e t c .

(d)

q u a l i t y c o n t r o l - p o l l u t i o n abatement, improvement of water q u a l i t y ,

prevention of contamination f o r the p r o t e c t i o n of the environment and of public health.

301 ( e ) b e n e f i c i a l use of land/water space - urbanization, improvement of a g r i c u l t u r a l and i n d u s t r i a l production, t r a n s p o r t including inland navigation, water power u t i l i z a t i o n , r e c r e a t i o n a l use of water and a e s t h e t i c enjoyment. Currently water development p r o j e c t s are planned f o r s e v e r a l purposes (Tab. 4.14;. The s~unof a l l the b e n e f i t s of a multi-purpose p r o j e c t exceeds the maximum b e n e f i t of any one i n d i v i d u a l function, but t h e v a l u e of any one of i t s funct i o n s i s seldom the mximun one. Some of i t s functions m y even be contradictory (Tab. 4.15). These contradictions may occur a f t e r t h e constriiction of r e s e r v o i r s ,

for example because they a f f e c t an extensive a r e a and t h e i r e f f e c t s d i f f e r (a) i n t h e space of the r e s e r v o i r and i t s environment (Tab. 4 - 1 6 ) , (b) along the water coiirse downstream of t h e dam (Tab. 4 . 2 0 ) , ( c ) along the headrace o r t a i l r a c e (Tab. 4.21), ( d ) i n the area under supply (Tab. 4 . 1 7 ) . TABLE 4.14

-

1,2

2

1,2

0

2

29 3

293

Hydropower Fenera t i o n

1,2

-

2

1,2

2

2

2

2

NaviKa t i o n

2

2

-

0

3

3

0

0

2

0

3

0

Ida ter supply

Flood c o n t r o l

1,2

1,2

0

-

\dater q u a l i t y con t r o 1

0

2

3

2

-

0

3

3

Environmen t a 1 and a e s t h e t i c aspects

2

2

3

0

0

-

0

0

Recreation

2,3

2

0

3

3

0

-

3

Fish breeding

2,3

2

0

0

3

0

3

-

- no o r non-important variance 1 - variance i n reservo+ v o l m e . requirements 2 - variance i n reservoir operation requirements 3 - variance i n water q u a l i t y requirements 0

Matrix of variances f o r b a s i c purposes of reservoir construction and operation.

302 TABLE 4.15

~~~~

~

Reservoirs i n populated areas

1 1 1 2

1 3 2

0 2

1 1 0 3

6 3

Reservoir i n abarldoned areas

1 1 1 1 1 3 0 0 2 1 1 2 0 7 2

Flood c o n t r o l dikes R ive r tr a i n i n g

0 0 0 1 1 0 3 0 1 0 0 0 1 4 0 0 3 3 1 1 2 2 0 1 2 2 2 3 3 5

Bank s t a b i l i z a t i o n

0 0 0 1 1 0 0 1 1 0 0 0 1 5 0

Water ways

0

3

1

1

1

0

2

0

2

2

2

2

3

3

5

Irrigation projects Irriga tion

0

0

0

1

0

2

2

1

1

2

0

2

0

3

4

Dra ina ge

0

0

0

1

1

3

1

0

1

0

0

3

0

4

0

Fishponds

1

0

0

1

3

3

1

0

3

1

1

3

3

5

0

S a n i t a r y eng. p r o j e c t s LJa t emork s

1

0

Sewarage

0

0

Groundwater development Water r e c y c l i n g

0 0 1 0 0 1 0 0

1 0 2 0 0 0 0 0 0 0 2 1 1 0 2+0 1 0 0 0 0 0 2 1 1 0 0 3 0 3

0 0 3

0 2

0

1

0

0

0

0

1

0

0

0

0

0

3

Water management measures Afforestation

0 0 0 3 1 1 1 1 2 1 0 1 0 6 1 0 0 0 3 1 1 1 1 2 1 0 1 0 6 1

Managed a a i c u l t u r e

0 0 0 1 0 0 1 1 1 2 0 2 0 4 2

DiverEencies i n the impact of s e l e c t e d water p r o j e c t s and measures: 0 - no o r unimportant infl,.ience, 1 - p o s i t i v e impact 2 - negative impact, 3 - depends on l o c a l conditions, + with a waste water treatment 'plant

303

4.6.1

E f f e c t s of Reservoirs and I r r i g a t i o n 9;stems on C1imt:e

The flooding of an area a f t e r p u t t i n g a r e s e r v o i r i n t o operation changes ' t h e c h a r a c t e r of the landscape. A uniform, compact water t a b l e takes t h e place of d i v e r s e surfaces of d i f f e r e n t c h a r a c t e r . I n such a way the r e s e r v o i r a f f e c t s a l l the n a t u r a l processes which took p l a c e w i t h i n i t s area of influence. The o r i g i n a l evapotranspiration of ecosystems and t h e evaporation from bare s o i l s a r e replaced by t h e increased evaporation from the f r e e water s u r f a c e , whose s h a r e was o r i g i n a l l y f a r l e s s important. This process is thus released from a dependence on s o i l , hydrogeological and physiological f a c t o r s . TABLE 4.1 6 Impact of r e s e r v o i r s on t h e i r surroundings

Flooded land

Flora and Fauna

Water q u a l i t y

Microclirrate

Dwelling value

Rise i n water t a b l e , increased fluctuation

Change i n aquatic l i f e

Abrasion

Rise i n a i r humidity

New scenery

Loss of a g r i -

Development of plankton organisms

Sedimentation

Equalizing temperature differences

Improvement of l i v i n g and recreational conditions

Mew predominant f i s h species

Production of new organic matter

Increased wind velocity

Increase i n i n s e c t density

Temperature changes

Change of albedo,energy input and radiation

Increase i n popul a t i o n density and i n p o l l u t i o n

c u l t u r a l and f o r e s t land

Flooded mineral resources

Rise i n ground Change i n water t a b l e and c o a s t a l . increase i n vegetation infiltration Increased probability of earthquake occurrence

Change i n wild1 i f e species including fowl

Mineralization, Decrease i n zones of local rainfall different water q u a l i t y

Flooding of landmarks and monuments

Checklist of the probable impact of r e s e r v o i r construction and operation of the surroundings. The r i s e i n a l t i t u d e of the s u r f a c e a t which evaporation occurs, i t s less 'protected p o s i t i o n and its smoothness a l l a c c e l e r a t e t h i s process and a f f e c t t h e

304 a i r flow. The increased i n p u t of s o l a r enerEy, i . e . the change of the albedo and t h e i n c r e a se i n the wat er temperature, may a l s o c o n t r i b u t e t o the r i s e i n the evaporation r a t e . The s i m p l i f i c a t i o n of s u r f a c e c h a r a c t e r i s t i c s , the decrease in e v a p o t r a n sp i r at i o n , the i n cr eas e i n a i r humidity change re ve rse ly the conditions which i n f l u e n ce t h e run o f t h i s process. Depending on meteoroloyical and o t h e r c onditions, the evaporation from the f r e e water s u r f a c e mostly exceeds the ev a potra nspira tion from a f f o r e s t e d o r c u l t i v a t e d s o i l s . Both evaporation and eva potra nspira tion from the a djoining shore a r e a s i n c r e a s e , due t o t h e r a i s e d moundwa ter ta ble being s u f f i c i e n t l y s u p p l i e d by t h e impounded water t a b l e of the r e s e r v o i r . A s i m i l a r inc re a se i n e v a p o t r a n sp i r at i o n is recorded along i r r i g a t i o n c a na ls. The i n c r e as e i n evaporation a l s o i n f l u e nc e s the water q u a l i t y , causing nonproductive water l o s s es and r a i s i n g the c onc e ntra tion of suspended and dissolved m a t t e r . This f a c t i s extremely important i n a r i d and semi-arid a r e a s because of the extremely high evaporation r a t e t h er e. The f a l l i n water q u a l i t y occurs a s a consequence of high evaporation, e s p e c i a l l y i n shallcw r e s e r w i r s . I t may r e s u l t i n a drop of wat er q u a l i t y b e l m t h e l i m i t s of u t i l i z a t i o n f o r the re quire d purpose, o r l i m i t the economic f e a s i b i l i t y of the r e l e v a n t p r o j e c t . The i n c r e a s e i n the mean evaporation from an a r e a a f f e c t e d by the c onstruc tion of a r e s e r v o i r can be estimated on t h e b a s i s of the following equation: E

.A

E = r E

=

=

EN.Aw + ET . (A-Aw)

. EIJ

+ ET.

ET + r

(m3)

(1-r)

(m)

. (I3.I-ET)

(m )

- area surface A, - water t a b l e s u r f a c e

(m* ) (m2)

E - t o t a l mean evaporation ET - mean e vap o t r an s p i r at i o n from the s o i l s u r f a c e

fm)

A

md - mean evaporation frcm f r e e water s u r f a c e

r=

$-

the r a t i o of the water t a b l e s u r f a c e

(4.14)

&

(4.15)

(m) and the a r e a s u r f a c e A

Leaving a s i d e the chanpe of t h e p r e c i p i t a t i o n t o t a l and the change of mean evaporation, the decrease i n the t o t a l y ea rly runoff from a catchmerit r e s u l t i n g

from the increased evaporation reaches dQa= d . (FV - ET) . A d = rl-ro

-

(m3)

(4.16)

the d i f f e r e n c e between the r a t i o of the water surfa c e and the SUT face of t h e catchment a f t e r f r l ) and before (yo) the c onstruc tion of the r e s e r v o i r

The decrease i n the t o t a l y ear l y runoff due t o the impact of the c onstnic tion of an i r r i g a t i o n

network can b e estimated i n a s i m i l a r way, i n accordance with equations 4.14 and 4.16. I n t h i s cas e

305 4.17

TABLE

Impact of i r r i g a t i o n (drainage) soil profile

Chemical impact

Fiologica 1 1mpac t

Hydrological impact

M i c r o c l i m te

Rise i n the (drop i n t h e ) groundwater table

Change i n acidity or alkalinity of s o i l

Increase (decrease) i n the r o o t depth

Increase i n runoff

Change i n t h e albedo ( i n both c a s e s )

IJe t t i n g ( a e r a t i o n ) of the s o i l profile

Increase (decrease) i n the s a l i n a t i o n rate

Increase (decrease) i n respiration of r o o t s

Increase i n (suppression o f ) evaporation

Increase (decrease) i n the a i r humidity

Change i n the s o i l temperature

(Escape of nutriments, especially n i troqen)

P l a n t d i s e a s e s Decrease provoked by (increase) i n h i p h e r humidity i n f i l t r a t i o n

cooling (warming)

Change i n the plant species ( i n both cases), weed occurrence

Decrease i n the d a i l y fluctuat i o n of tempera t u r e

Change i n t h e s o i l structure

Increase i n (suppress i o n of) insect occurrence C h e c k l i s t of the probable impact of i r r i g a t i o n and drainage ( i n b r a c k e t s ) on the water c y c l e and t h e environment.

ETo

-

mean e v a p o t r a n s p i r a t i o n from the dry-farmed and o t h e r non-irrigated land

(m)

ETi - w a n e v a p o t r a n s p i r a t i o n from i r r i g a t e d land

(m) the r a t i o of the i r r i g a t e d land A; and the t o t a l a r e a s u r f a c e A

ri

=

Ai

-

ro

=

G

and t h e r e f o r e

A Q a i = ri

. (ET;

- ET,)

.A

(m3>

(4.17)

The increased y i e l d a f t e r i r r i g a t i o n is o f t e n achieved less by t h e growth i n the overall

e v a p o t r a n s p i r a t i o n r a t e , b u t r a t h e r by the d i f f e r e n t and more e f f i c i e n t

evaporation d i s t r i b u t i o n : by i t s i n c r e a s e i n t h e period of p l a n t growth and by

its decrease o u t of the v e g e t a t i o n season, i . e . by the i n c r e a s e i n e f f i c i e n t and

306 decrease i n i n e f f i c i e n t evaporation. This phenomenon has Seen confirmed sta tist i c a l l y by long-term measurements, e.g. the water t a b l e of the Aral Sea did not change i n the period 1910-60, i n s p i t e of the extension of the i r r i g a t e d area from 2 t o 4 m i l l . ha i n the catchment of i t s t r i b u t a r i e s . From t h i s p o i n t of view an a p p r o p r i a t e cropping pa ttem, c o r r e c t i r r i g a t i o n timing and appropria te economic i r r i g a t i o n p r a c t i c e s a r e a l s o important. I n the step-by-step

develop-

ment of i r r i g a t i o n , t h e r e f o r e , two s t a g e s can be d i s t i n m i s h e d - s t a g e of evaporation r e d i s t r i b u t i o n , n o t a f f e c t i n g the t o t a l annual runoff to a s i m i f i c a n t extent, s t a g e of increased t o t a l evaporation, decreasing the t o t a l annual runoff.

-

The increase i n the e x t e n t of f r e e water surfaces i n the catchment owing to the construction of r e s e r v o i r s o f t e n r e s u l t s i n a reduction i n p r e c i p i t a t i o n . This decrease i n p r e c i p i t a t i o n is a consequence of l a g e r temperatures above the water s u r f a c e i n the simer season i n c m p a r i s o n with the o r i g i n a l temperatures above the n o n w e t t e d s o i l s u r f a c e . The decrease i n the t o t a l yearly runoff may, t h e r e f o r e , be higher than the value e s t a b l i s h e d according t o equation ( 4 . 1 6 ) . An inversion o f t e n occurs above an open water surface: the a i r temperature does n o t f a l l with increasing a l t i t u d e , but rises. This inversion causes a v e r t i c a l a i r motion, decreasing the r a t i o of i t s s a t u r a t i o n - and hence t h e probabil i t y of r a i n f a l l occurrence, too. This p r o b a b i l i t y is a l s o reduced by the reduced rouzhness of the r e s e r v o i r s u r f a c e i n comparison with the roughness of the o r i g i n a l land s u r f a c e . The decrease i n the t o t a l r a i n f a l l has been recorded s t a t i s t i c a l l y , b u t only i n the case of extremely b i g r e s e r v o i r surfaces. This a l s o s i g n i f i e s a decrease i n the water exchange i n the t o t a l annual runo f f of a f f e c t e d water courses, e s p e c i a l l y i n the case of b i g carry-over storages, which has a n important impact on water q u a l i t y . This e f f e c t of the operation of b i n carry-over s t o r a g e s has already been recorded on a global s c a l e . The c o n s t r u c t i o n and consequent operation of r e s e r v o i r s and i r r i g a t i o n networks a l s o influences the values of o t h e r meteorological phenomena, i n comparison with the o r i g i n a l s t a t e without any reserwir o r i r r i g a t i o n . The h e a t capacity of water is four t o f i v e times h i g h e r than t h a t of a i r o r s o i l and rocks, and the l a t e n t h e a t of s o l i d i f i c a t i o n and evaporation is also comparatively high. Water bodies a c t , t h e r e f o r e , a s a cooler p a r t of the environment during a rapid increase i n a i r temperature, e . g . i n s p r i n g and during the morning hours. During a f a s t f a l l i n a i r temperatures, e.g. i n the evening o r i n a u t u m , they function a s a warmer p a r t of the environment. Likewise, they warm the adjoining a i r layer during cool summer n i g h t s . The h e a t of the water body l i m i t s the f l u c t u a t i o n of the temperature of the s u r f a c e a i r l a y e r , a l s o influencing the thennic zonation of the a i r on t h e r e s e r v o i r shore. This influence can be measured e s p e c i a l l y i n deep v a l l e y s , and has a d i f f e r e n t impact depending on the r a d i a t i o n s i t u a t i o n . During r a d i a t i o n back t o space,

3 07 which occurs p a r t i c u l a r l y during b r i g h t n i g h t s , the lowest temperatures i n a v a l l e y without a r e s e r v o i r a r e a t the foot of the s l o p e , when calm. Lmer mini-

m m n i g h t l y temperatures a l s o occur i n t h i s zone. I n the middle p a r t of the s l o p e a warmer zone with higher values of minimum n i g h t l y temperatures appears. A t the top of the s l o p e , the temperature decreases again (Fig. 4.14 a , b ) .

I n a v a l l e y with a r e s e r v o i r the n i g h t temperature decreases upwards t o the top of the s l o p e . The d i f f e r e n c e between day and n i g h t temperatures i n a valley with a r e s e r v o i r is higher a t t h e top of the s l o p e , but a t its f o o t i n a valley without a r e s e r v o i r . I n a v a l l e y with a r e s e r v o i r , a more i n t e n s i v e wind motion occurs, because warmer a i r above the water t a b l e is replaced by cooler s t r a t a which descend from t h e top of the slope.

Fig. 4.14. The course of a i r temperatures ( d a i l y ) Td, n i g h t l y Tn) the temperat u r e of the s o i l s u r f a c e Ts and of a i r humidity I J i n a v a l l e y :a) before and (b) a f t e r the c o n s t r u c t i o n of a r e s e r v o i r during r a d i a t i o n s i tuaLion according to Ma19 (1979). A i r motion above the r e s e r v o i r shore during calm; ( c ) c l e a r day, (d) c l e a r n i g h t . The occurrence of the inversion I and fog F: R - r e f l e c t e d r a d i a t i o n , CA - cool a i r , TJA - warm a i r , C - a i r c i r c u l a t i o n , E - evaporation.

3 08 On a b r i g h t day, the h i g h e s t temperatures occur a t the f o o t of t h e slope i n a

v a l l e y without a r e s e r v o i r

and decrease upwards t o the top of the slope. I n a

v a l l e y w j th a r e s e r v o i r , the h e a t capacity of the water body reduces the morning temperatures. Their decrease t o the top of the slope is measurable when windy (Tw), and n e g l i g i b l e when calm (Td). The a i r flow depends on the changes of temperature. The lower roughness of the r e s e r v o i r s u r f a c e promotes h o r i z o n t a l a i r movement. The influence of b i g res e r v o i r s therefore changes the shape of t h e r e l e v a n t wind r o s e , increasing the occurrence of s t r o n g winds from the reservoir to the shore, namely alonE i t s longest dimension. The wind r o s e is extended i n t h i s d i r e c t i o n . The a i r movement is more marked i n shallow v a l l e y s , while i n deep valleys t h i s only a p p l i e s i n the case of a coincidence i n the d i r e c t i o n of the v a l l e y and the p r e v a i l i n g s t r o n g winds. During calm and durinp r a d i a t i o n back t o space i n the s p r i n g season i n daytime, the warmed a i r r i s e s above the r e s e r v o i r ' s shores, being replaced by the cooler a i r coming from the expanse of the r e s e r v o i r i t s e l f . This cooler a i r is replaced by t h e s t i l l cooler a i r from the upper i a y e r of the amnosphere (Fig. 4.14 c ) . The a i r humidity depends on the evaporation r a t e . I n a f l a t a r e a a n influence of some 10 - 15%of the r e l a t i v e humidity reaches t o a d i s t a n c e of some 100 m i n the d i r e c t i o n of t h e wind, even i n the case of r e l a t i v e l y small r e s e r v o i r s . The h i g h e s t a i r humidity is a t the r e s e r v o i r s u r f a c e , and t h i s decreases towards the top of the s l o p e i n deep v a l l e y s . The course of thp a i r humidity i n valleys witho u t r e s e r v o i r s is the reverse: its values a r e about 3% lower a t the f o o t of the s l o p e than a t i t s top. The high a i r humidity a t the water t a b l e and the occurrence of the inversion l a y e r r e s u l t i n fog formation where the cool a i r flaws i n , thus increasing the frequency of fog occurrence i n v a l l e y s w i t h r e s e r v o i r s - o r l a r g e headrace, tailrace and diversion c a n a l s , e s p e c i a l l y during periods without winds (Fig. 4.14 d ) . The degree of influence of a r e s e r v o i r on the l o c a l climate therefore depends on the frequency of wind occurrence and on i t s i n t e n s i t y . The change of the microclimate a l s o depends on the change of t h e s o l a r r a d i a t i o n input and on i t s r e f l e c t a n c e , derived from the change of the a r e a s u r f a c e . D i f f e r e n t species of the v e g e t a t i v e canopy a r e replaced by the uniform water t a b l e , whose r e f l e c t a n c e depends on the angle of incidence. Changes of the absorption and r e f l e c t a n c e of s o l a r r a d i a t i o n , together with changes of temperature and humidity, a l s o influence the ecosystems on the shore i n question. The energy i n p u t i n c r e a s e s , producing favourable e f f e c t s on the relevant canopy, a s long a s the limits of i t s h e c t tolerance a r e n o t exceeded. The e x t e n t of the measurable e f f e c t of r e s e r v o i r operation on climatological f a c t o r s depends on the l o c a l conditions. It i s a compensating e f f e c t , occurring more noticeably i n a r e a s with a rough climate than i n a r e a s with a mild climate.

309 The d i s t a n c e of reach of t h e c l i m a t o l o g i c a l i n f l u e n c e of r e s e r v o i r s and irrig a t i o n networks depends on t h e i r s i z e : I t does n o t exceed a few hirndred meters i n t h e c a s e of s m l l r e s e r v o i r s . Rig r e s e r v o i r s influence the c l i m a t e w i t h i n a reach of some 1 to 3 km from t h e i r s h o r e s . The b i g g e s t r e s e r v o i r s i n the world, according t o Avakyan e t a l . (1977), can under extraordinary meteorological cond i t i o n s o c c a s i o n a l l y i n f l u e n c e the c l i m t e

JJ

t o a d i s t a n c e of 30 t o 60 km, t h e i r

averape e f f e c t g e n e r a l l y o c c u r r i n g w i t h i n a reach s f 10 t o 15 km. Th? change of mesoclimate

and s a n i t a r y hazards caused waterlogging, wrong i r r i g a t i o n p r a c t i c e s

e t c . are more important, because of i n h a b i t a n t s

l i v i n g i n s i d e the a f f e c t e d a r e a .

E f f e c t of Reservoirs and Dams on Sediment Transport

4.6.2

Dams, d i v e r s i o n dams and weirs i n h i b i t and d i s r u p t bed-load,

siispended and

wash load t r a n s p o r t . They a l s o change t h e course of t h e erosion process both downstream and, w i t h i n t h e reach of t h e i r s w e l l i n g e f f e c t , upstream. Tne process of sedimentation i n r e s e r v o i r s occurs a s a consequence of the decrease of the v e l o c i t y and k i n e t i c energy of flow i n t h e e s t u a r i e s of t r i b u t a r i e s running i n t o the r e s e r v o i r . The

i n c r e a s i n g depth and extensiori of t h e cross s e c t i o n r e s u l t s

i n a r e d u c t i o n i n t h e sediment t r a n s p o r t c a p a c i t y of the flm. The d i f f e r e n c e i n t h e o r i g i n a l qo and the r e s u l t i n g t r a n s p o r t c a p a c i t y , q r , n u s t be deposited, or A q r = (qo - 4,) Aqr

-

(m3

(4.18)

the difference i n the transport cap a c itie s, deposited w i t h i n the reach

(m3)

This d e p o s i t i o n process takes p l a c e by a f f e c t i n g the c a r s e p a r t i c l e s of the sediment mixture and those p a r t i c l e s w i t h t h e h i g h e s t u n i t mass f i r s t , the f i n e s t ones w i t h a low u n i t mass last. This leads t o s e g r e e a t i o n of sediments of d i f f e r e n t s i z e and d e n s i t y . The g r a v e l , t h e boulders and p a r t i a l l y a l s o t h e sand which move as bed load form d e l t a s , sometimes r e f e r r e d t o a s backwater d e p o s i t s , a t a r e l a t i v e l y short. d i s t a n c e frcm the e s t u a r y . Deltas extend t o t h e p o i n t where the maximum water l e v e l i n t e r c e p t s the o r i g i n a l river bed. Rorland (1971), a f t e r i n v e s t i g a t i n g the d e p o s i t i o n a l p a t t e r n of d e l t a formation, concluded: - t h e t o p s e t s l o p e approximates one h a l f of the o r i g i n a l s l o p e ,

-

t h e f o r e s e t s l o p e i s 6.5 times the t o p s e t s l o p e , the t o p s e t and f o r e s e t s l o p e s meet a t the normal o r mean pool where t h e r e s e r voir is operated most of t h e time.

Seasonal d r a w d m causes the formation of multi-deltas. Suspended load, mostly sand and o t h e r anorganic and organic p a r t i c l e s , wash load, i . e . s i l t , c l a y , agrochemical p a r t i c l e s and c o l l o i d s , which move predomi-

310 n a n t l y i n suspension and have the k i n e t i c energy of the flowing water, become more and more a f f e c t e d by g r a v i t a t i o n a l forces with the decreasing v e l o c i t y of flow. F i n e r m a t e r i a l forms the bottom sediments, spreading throughout the r e s e r v o i r . The average thickenss of the deposition hdi per u n i t time of deposition td was specified a s : (4.19) Ai

-

a r e a between th? siiccessive s e c t i o n s , corresponding t o the d i f f e r e n c e i n transport capacitiesaq .. ri

The f i n e s t p a r t i c l e s of s i l t , c l a y , c o l l o i d s e t c . ( o f t e n f l o c c u l a t e d ) a r e a l s o a f f e c t e d by the dynamic Viscosity of water and, t h e r e f o r e , s i n k t o the bottun very slowly. They have a tendency t o form d e n s i t y c u r r e n t s , which have been found t o move towards the s p i l l w a y s , turbines and o u t l e t s . I n a d d i t i o n to t h i s , thixotrop pel o f t e n forms the mass which a c t s a s a s o l i d when a f o r c e is n o t a p p l i e d b u t w i l l f l m when a force is a p p l i e d . F l o a t i n g debris rest i n the zone where the t r a c t i n p forces a r e i n equi1ibri.m with the r e s i s t a n c e of wind. ( F i g . 4.18) The p r a i n s i z e , i t s unit mass and shape a r e the b a s i c f a c t o r s which influence i t s mobility and determine whether p a r t i c l e s w i l l s e t t l e or n o t . The water dens i t y i n the r e s e r v o i r i s heterogeneous, a l s o depending on temperature. The relev a n t p a r t i c l e s s i n k u n t i l they reach a water l a y e r with the corresponding density o r r i p h t down t o the bottom. Depending on the d e n s i t y , s t r a t i f i c a t i o n and flow v e l o c i t y , some p a r t i c l e s which a r e n o t a b l e t o f l o a t i n the upper layers of the r e s e r v o i r s , cannot s e t t l e near the bottcm. The t h e o r e t i c a l d i s t a n c e of deposition Ls f o r a p a r t i c l e with a s e t t l i n g

velocitv L

S

w , derived f o r a s t a b l e depth and width

= H - WV

(4.20)

w - v e r t i c a l sedimentation r a t e , depending on t h e u n i t mss, s i z e and shape of, t h e p a r t i c l e s !see eq. 2.15) (m.s-’) v - flow r a t e

H

-

depth of t h e r e s e r v o i r i n a piven place

(m . s-l)

(m)

For a r e s e r v o i r with varying depth and width the d i s t a n c e i s (4.21) because both t h e depth and the flow r a t e a r e functions of the d i s t a n c e of the e n t r y of t h e sediment p a r t i c l e i n t o the r e s e r v o i r .

311 Then the f l o w r a t e i n c r e a s e s , e . g . i n the period of t h e decrease i n water t a b l e i n a r e s e r v o i r o r during floods, p a r t i c l e s of t h e same s i z e s e t t l e a t g r e a t e r d i s t a n c e s , d e s t r o y i n p i n t h i s way the homogeneity of t h e grain-size dist r i b u t i o n , which i s a l s o influenced by the s u r f . Only those p a r t i c l e s cross the dam p r o f i l e which happen t o h e i n the reach of the k i n e t i c e f f e c t of the o u t l e t s , off-takes and spillways

(Fig. 4 . 1 8 )

s-%

10'

10'

10'

10

1

Fig. 4.15. Trap e f f i c i e n c y curve according t o Rrune (1979): s - sediment trapped as a percentage, r - r a t i o of r e s e r v o i r capacity t o mean annual flow, v - envelope curves; c - coarse sediment, f - f i n e sediments, m - medium curve. The deposition of transported bed-load, suspended load and wash load i n res e r v o i r s r e s u l t s i n the s t o r a g e loss. Trap e f f i c i e n c y , t h e a b i l i t y of a reservoir

t o t r a p and/or retain the sediment which e n t e r s i t , can be expressed a s a p e r cer?tage of the t o t a l load. (FiE. 4.15). For very l a r g e r e s e r v o i r s , the t r a p e f f i c i e n c y is almost 100 per c e n t , because only very f i n e sediments can pass the barrage. To determine the sediment d e p o s i t volume Roosebocm (1975) recomends the expression Vt

= V50

for t Vt

V50

>

.

0.376

.

t

In

(m3 )

33

(4.22)

8 years.

- the average sediment volume a f t e r t years

-

t h e a r b i t r a r y estimated sediment volume a f t e r 50 y e a r s .

The r e s e r v o i r operation a l s o influences the d e n s i t y , i . e . the average u n i t mass of d e p o s i t s . The average u n i t mss f o r a d e p o s i t over a period of t years

is given by Pemberton (1980) =

ri +

0.43. K

.[-. t

Iti - i n i t i a l u n i t mass

In t

- 11

(kg/m3)

(kn/m3)

(4.23)

3 12

rt - r e s u l t i n e u n i t

mass over a period of t ye a rs

K

- Lane-Koelzer f a c t o r (Table 4.18)

t

- period

TABLE

(kg/m3)

(years 1

4.18 ~

Type of r e s e r v o i r opera t i o n

_

_

_

_

~~

I n i t i a l mass,

Idi

Jaye-Koelzer f a c t o r K

cl ay

silt

sand

clay

silt

sand

Sediment submerped

416

1120

1550

256

91

0

‘bdera te t o c o n s i d er ab l e drawdm

561

1140

1550

135

29

Normally empty

641

1150

1550

Rivered sediments

961

1170

1550

I n i t i a l u n i t mass, Wi and K f a c t o r s (ke.m 3 ) according t o Lane and Koelzer (1975). Formulas f o r the es t i mat i o n of t h e t r a p e f f i c i e n c y of r e s e r v o i r s ofte n have an exponential form, considering t h a t , i n the f i n a l s t a g e , the arrangement of the r e s e r v o i r and the flow r a t e do n o t allow f u r t h e r sediment de position. According t o Gontcharcw (1960)

Vt - the d e c r eas e i n reservoir volume through sediment

d e p o s i t du r i n g T y ear s

(m3

orig.inal volume

(m3)

V

-

V

- mean annual sediment d e p o s i t volume i n the r e s e r v o i r (m3 p e r ye a r)

t

- period

Y

(ye a rs)

The mean annual sediment d e p o s i t V i n a r e s e r v o i r is simply Y

v

=

s . R, 8,

Y

+-

‘b

(rn 3 /year) (4.25)

‘b

Rsw

- medium t o t a l annual t r a n s p o r t of the suspended and wash l o a d

S

-

c o e f f i c i e n t of t h e t r a p e f f i c i e n c y

F+,

-

medium t o t a l t r a n s p o r t of t h e bed load

( t pe r ye a r)

( t pe r ye a r)

3 13

4, - u n i t

mass o f the suspended and wash load

rb- unir: mass

of the bed load

("1.7

' h e medium t o t a l annual t r a n s p o r t R catchment Rsw =

CBR

be derived on t h e basis

s .Ac. se. i

31536. ca

=

(NO. 7 t t m-3)

of the suspended and wash load from a sw of the main catchment c h a r a c t e r i s t i c s

. Q,

(t/year)

(4.26)

AC

-

catchment a r e a

(m2)

ie

-

annual e r o s i o n r a t e i n the catchment a r e a

( t h-2 /yea r )

.

ca - average c o n t e n t of suspended and wash load i n the discharqe

(t.m-3>

0, - mean annual discharge

( m 3 . s-l)

e

-

ss

-

s

s h a r e of the eroded m a t t e r forming the suspended and wash load

( < 1)

s h a r e of the suspended load t h a t has n o t s e t t l e i n the mediate r i v e r s t r e t c h

(< 1 )

% 100 W

5 3

J

0

> 80

-

[L

0

> a w

v)

W

60

[L

40 60

50

40

30 20 D I S T A N C E FROM D A M

FiR. 4.16 Geographical r e p r e s e n t a t i o n of sediment d e p o s i t i o n i n r e s e r v o i r s and the decrease i n s e t t l i n g r a t e . Sediments are b u i l t up t o a n e l e v a t i o n dependinp on s l u i c i n g l e v e l , b u t channel i s maintained through t h e s e . Mo - monolimnion, ce - c i r c u l a t i o n i n epilinmion. I t i s very important from the o p e r a t i o n a l p o i n t of view t h a t the r a t e of s t o r a g e reduction i s h i g h e r i n t h e i n i t i a l period of t h e r e s e r v o i r ' s operation

314 and depends on t h e g r a i n s i z e d i s t r i b u t i o n (Fig 4.15,. The bed load and coarse f r a c t i o n s of t h e suspended load a t t h a t time e n t e r t h e upper parts of t h e s t o r a g e only, reducinr: f i r s t the v o l m e of t h e s t o r a g e zone reserved f o r flood c o n t r o l and then, i n t h e second s t a g e , a l s o t h e conservation s t o r a g e . IJnder t h e s e circums t a n c e s only f i n e f r a c t i o n s a r e a b l e t o reach t h e i n e f f e c t i v e p e m r e n t s t o r a g e . For rivers with a r e g u l a r sediment t r a n s p o r t t h e coiirse of t h e decrease i n t h e t o t a l s t o r a g e may be considered a s l i n e a r : Vt

=

vy .

t

(m

3

(4.27)

I n t h e t h i r d phase o f t h e s t o r a g e reduction p r o c e s s , t h e movement o f t h e bed load reaches t h e i n e f f e c t i v e permanent s t o r a g e and then t h e dead s t o r a g e , decr e a s i n g the r a t e of reduction i n t h e a c t i v e ( f l o o d c o n t r o l and conservation) s t o r a g e . In t h e f o u r t h phase, t h e sediment t r a n s p o r t

e n t e r s t h e storaEe and t h e

space of t h e dynamic i n f l u e n c e of t h e t u r b i n e s , o u t l e t s and s p i l l w a y s , r e s u l t i n g i n a f u r t h e r d e c r e a s e i n t h e r a t e of diminuation o f the r e s e r v o i r volume ( F i g .

4.16). The rate o f s t o r a g e reduction by sedimentation depends e s p e c i a l l y on t h e proper design o f a p r o j e c t . Depending on t h e sediment t r a n s p o r t regime and on the requirements on r e s e r v o i r and dam o p e r a t i o n , a n optimum d e s i g h , i . e .

-

t h e s i z e of t h e reservoir and

-

a l a y o u t of t h e p r o j e c t ,

can be s e l e c t e d and r e a l i z e d i n such a manner t h a t almost no suspended and wash load i s k e p t back, w h i l s t s t o r i n g water i n t h e r e s e r v o i r . I n such a way only t h e t r a n s p o r t of t h e bed-load c o n t r i b u t e s t o t h e s t o r a g e reduction. The sedimentladen water o f t h e e a r l y flood is passed through low-level openings. This condit i o n r e q u i r e s a r e l a t i v e l y shallow r e s e r v o i r and a r e l a t i v e l y s h o r t r e s e r v o i r lake, n o t f i l l e d except i n l a t e f l o o d , when the flood water contains l e s s sediments. The dynamic i n f l u e n c e o f r e l e v a n t s p i l l w a y s and o u t l e t s must reach t h e sediment f l m . Their capacity, arrangement and r e l e v a n t o p e r a t i o n With t h e g a t e s

must n o t permit a d i v i s i o n of t h e s t r e a m l i n e , r e s u l t i n g i n a reduction i n t h e t r a c t i n g f o r c e s . An a p p r o p r i a t e s i z e , lay-out and equipment of t h e p r o j e c t ena b l e s t h e r e s e r v o i r t o i n t e r f e r e t o some 10%w i t h t h e regime of r i v e r s with a high level of suspended m a t t e r t r a n s p o r t , thus g r e a t l y c o n t r i b u t i n g t o t h e efficiency of the project. Other c o n t r o l measures can be grouped i n - c o n t r o l o f watershed (proper soil conservation, farming and f o r e s t i n g techniques, p r o t e c t i o n of r i v e r banks e t c . )

-

c o n t r o l o f inflow (by s e t t l i n g b a s i n s , by-pass c a n a l s , p r o v i s i o n of v e g e t a t i v e

screening, favourable l o c a t i o n of i n t a k e s t r u c t u r e s f o r off-channel reservoirs etc.)

315 -

removal of d e p o s i t s ( f l u s h i n g , s l u i c i n g , dredging, which i s economic i n

exceptional cases o n l y ) . The decrease i n r e s e r v o i r volume n o t only resLlts f r a n the sediment of the r e s e r v o i r ' s t r i b u t a r i e s , h u t also from the f a l l - o u t from t h e atmosphere, plankton,

washed up s o i l and a g r o c h m i c a l p a r t i c l e s from the a d j o i n i n p s h o r e s and

m a t e r i a l frcm the eroded r e s e r v o i r banks. The abrasion and l a n d s l i d i n g of shores

is a process of t h e i r d e s t r u c t i o n which is caused by the e f f e c t of water, wind, by the f l u c t u a t i o n of the water t a b l e , h y water flow, by the e f f e c t of waves and i c e and by the e f f e c t of human a c t i v i t i e s .

H

(rn)

0

time 100 O/O

Fig. 4.17. The e r o s i o n of r e s e r v o i r shores i n r e l a t i o n t o the f l u c t u a t i o n of the s t o r a g e l e v e l . z e d r a f t e d accordinp to Bayer ( 1 0 5 4 ) , 3 - pond l e v e l , F',axP intx-imim water l e v e l , A - a b r a s i o n s h o r e , l3 - s!iding a b r a s i o n s h o r e , C - shore with aCcUmUlation .Of sediments, B+C - a b r a s i o n and a c r i ~ r ~ i i l a t is~hno r e s .

An important d e s t m c t i v e e f f e c t is e x e r t e d e s p e c i a l l y by v a r i a b l e phenomena. The abrasion of the shores of a r e s e r v o i r starts s h o r t l y a f t e r the f i r s t f i l l i n g - u p of t h e r e s e r v o i r . The r a t e of t h i s process i n c r e a s e s step-by-step years of o p e r a t i o n , reaching a peak a f t e r

i n the f i r s t

sane t h r e e t o f i v e years and then

gradually, d e c r e a s i n g a g a i n . I n t h i s phase, t h e shape of the shores almost reaches a s t a t e of geomechanical equilibrium. The w e t t i n g of t h e shores r e s u l t s i n a change i n t h e i r geomechanical charact e r i s t i c s , e s p e c i a l l y i n t h e i r cohesive s t r e n g t h and c o e f f i c i e n t of f r i c t i o n .

New f o r c e s a c t i n g on t h e wetted m a t e r i a l d e s t r o y t h e o r i g i n a l balance, which may, under unfavourable geomorphological c o n d i t i o n s , a l s o r e s u l t i n the s l i d i n p of whole rock formations. Depending on t h e s l o p e of the s h o r e s , t h e i r exposure, t h e i r geological and s o i l c h a r a c t e r i s t i c s and t h e i r v e g e t a t i v e canopy, t h e r e s u l t of the process on

316 the shore formation a r e - abrasion w a t e r s i d e s , generally having a s t e e p s l o p e , whose m a t e r i a l i s eroded, transported and then deposited (Fig. 4,17 A) - abrasion and s l i d i n g watersides, when the change of gemechanical f a c t o r s r e s u l t s i n l a n d s l i d i n g (Fig. 4 . 1 7 B)

- accumulation w a t e r s i d e s , formed i n f l a t a r e a s , e s p e c i a l l y i n shallow coves, where t h e m a t e r i a l f r m t r i b u t a r i e s was deposited by wave a c t i o n (Fig. 4.17 C) - abrasion and accumulation watersides, which a r e s t e e p , with a platforni formed by the eroded m a t e r i a l . Abrasion phenomena do not occur whenever the slope of the shore is h e l m 3'. TJnder such conditions the a c t i n g f o r c e s , because of t h e i r almost p a r a l l e l direct i o n , a r e n o t a b l e t o destroy the surface l a y e r . E f f e c t of Reservoirs on Water Qliality

4.6.3

The sedimentation process i n a r e s e r v o i r i s accompanied by many o t h e r physic a l , chemical and b i o l o g i c a l processes of s e l f - p u r i f i c a t i o n , which causes mixing and thinning. 'The influence of the water l e v e l f l u c t u a t i o n on t h e mean conc e n t r a t i o n of dissolved m a t t e r i n the r e s e r v o i r can be determined on the b a s i s of the following formula (4.28)

q,,

qo

vt,

Vo

- concentration of dissolved m a t t e r i n t h e moment 0 and to

0

t t

- volume of s t o r a g e i n the moment 0 and to

(m )

(m3 )

- concentration of dissolved matter i n the inflow water

-

outflow frcm t h e r e s e r v o i r i n the period from

1-5

3

Q t - water inflow i n the period from 0 t o t-1

k

(g.

(g.1-l)

0 t o t-1 (m3 )

I n t h i s formula a constant concentration of outflcw is assumed during the period i n question. Chemical and b i o l o g i c a l processes, running simultaneously with the physical processes, r e s u l t i n ( a ) t h e m i n e r a l i z a t i o n of organic matter ( b ) t h e production of new organic matter. Some chemical substances, e . g . c h l o r i d e s , do n o t change durinp these self-puri-

f i c a t i o n processes. T h e i r concentration depends then on the r a t e of water exchange. The concentration of o t h e r m a t t e r increases o r mostly decreases and can thus be expressed by a dropping exponential function, e.g. i n sumnary by means of t h e b i o l o g i c a l oxygen demand BOD. The course of the p h y s i c a l , chemical and b i o l o g i c a l processes

is influenced

317 n o t only by t h e i n p u t of sediments, b u t a l s o by the i n p u t of s o l a r energy and by t h e oxygen and carbon d i o x i d e from the a i r . The content of o r g a n i c m a t t e r depends on the r a t e of the m i n e r a l i z a t i o n processes and on the production of o r g a n i c matter. The dependence of the c o n c e n t r a t i o n of organic m t t e r i n the outflow on t h e rate of water exchange i s hyperbolic. This concentration depends on the c o n c e n t r a t i o n of t h e organic matter i n the inflow, on the average water depth, on the b i o l o g i c a l oxygen demand ROD5 i n the r e s e r v o i r and on the r a t e of t h e water exchange. According t o Stragkrabovs (1976)

q t - c o n c e n t r a t i o n of o r g a n i c m a t t e r i n t h e outflow

-

qr

c o n c e n t r a t i o n of non-disintegrable matter

qo - c o n c e n t r a t i o n o f o r g a n i c m a t t e r i n inflow

te

-

r a t e of water exchange i n t h e r e s e r v o i r

h

-

p

- ROD^

mean depth of the r e s e r v o i r prodiiction i n the r e s e r v o i r

(mg.R3D5.1-') (ma. I-') (mg . 1-l) (days) (m)

(g.m

-2

per day)

'The r a t e of m i n e r a l i z a t i o n process i n r e s e r v o i r s with a high r a t e of water exchange i s h i g h e r than t h e production of organic m a t t e r during t h e f i r s t f i v e days a f t e r the inflow of o r g a n i c matter. I n shallow r e s e r v o i r s , with a depth d a m t o 5 m and a r a t e of water exchange i n excess o f 20 days, the production of o r g a n i c m a t t e r exceeds the r a t e of m i n e r a l i z a t i o n . A s h o r t e r r a t e of water exchange r e s u l t s i n a h i g h e r decomposition r a t e . The longer r a t e of water exchange r e s u l t s i n an i n c r e a s e i n c o n c e n t r a t i o n o f organic matter i n t h e outflow i n comparison with t h e inflow, e s p e c i a l l y when t h e BOD c o n c e n t r a t i o n i n t h e inflow 5 is lower. The c o n c e n t r a t i o n of organic matter i n the outflow depends on t h e r a t e of production of t h e o r g a n i c m a t t e r i n comparison w i t h t h e rate of t h e mineralizat i o n process:

(4.30)

- r a t e of o r g a n i c production qP qm - r a t e of t h e m i n e r a l i z a t i o n process

(ma.

. 1-l)

(mg. 1-l)

For longer p e r i o d s of water exchange than 14 t o 16 days t h e s h a r e of dis-

318 Sediment

Fig. 4.18. The impact of thermal s t r a t i f i c a t i o n and operation with spillway g a t e s , bottom and inedirm o u t l e t s on water q u a l i t y i n r s e r v o i r . River flow t l , t2 and water c i r c u l a t i o n c during s t a g n a t i o n , c i r c u l a t i o n ch during t h e period of homothemicity i s dotted. The seasonal changes i n thermal s t r a t i f i c a t i o n .

i n t e g r a t e d organic matter does not depend on t h e depth of t h e r e s e r v o i r . The e f f i c i e n c y of t h e mineralization process increases with t h e duration of t h e water exchange and i n r e s e r v o i r s with a r a t e of water exchange of 14 t o 1 6 days increases s u b s t a n t i a l l y with t h e i r averape depth. The upper l a y e r s of t h e r e s e r v o i r a r e trophogemc, i .e. n u t r i t i v e . Assimilation

is t h e i r p r e v a i l i n g process, while d i s s i m i l a t i o n occurs only p a r t i a l l y . Lmer layers a r e t r o p h y l i t i c , i . e . they support the d i s i n t e g r a t i o n of organic matter. The p r e v a i l i w process there is d i s s i m i l a t i o n , when d e s t r u e n t s d i s i n t e g r a t e t h e dead plankton and o t h e r dead organisms. Owing t o the water flow a c e r t a i n development of p h y s i c a l , chemical and h i o l o g i u l processes is observed from the estuary of t r i b u t a r i e s t o t h e dam. The r a t e of t h e r e l e v a n t biochemical processes depends l a r g e l y on the course of water tenperatures. The u n i t mass of water depends on t h e temperature, chemi-

cal composition and content of sediments and r e s u l t s i n thermal s t r a t i f i c a t i o n . The p a t t e r n of t h e m 1 s t r a t i f i c a t i o n i n r e s e r v o i r s depends on t h e

- r e s e r v o i r depth and geometry - s o l a r r a d i a t i o n and a i r temperature - wind v e l o c i t y - r e s e r v o i r o p e r a t i o n , i . e . on t h e flow t o volume r a t i o .

319 The degree of s t r a t i f i c a t i o n depends on tlie densimentric Froude number Fr which can be approximated by

(4.31)

T,

-

PI

- mean r e s e r v o i r depth

Q

-

v

- reservoir volme

r e s e r v o i r lenptk discharge

According t o Canter (1983) i f F r i s less than

1 E ,

s t r a t i f i c a t i o n is expected,

with the depree o f s t r a t i f i c a t i o n i n c r e a s i n g with the d e c r e a s i n p densimetric Froude number. The thermal s t r a t i f i c a t i o n i n r e s e r v o i r s is more marked i n deeper r e s e r v o i r s . The d i f f e r e n c e i n temperature between t h e s u r f a c e and t h e bottom l a y e r s may exceed 15OC diirine high siimner and 10°C diiring s p r i n p . This d i f f e r e n c e i s about 4-5OC d u r i n g w i n t e r .

Temperature g r a d i e n t s , i . e . t h e d i f f e r e n c e of temperature i n t h e v e r t i c a l d i r e c t i o n , a r e n o t regiilar. Idhen t h e temperature regime i s s t a b l e , a c h a r a c t e r i s t i c zone c a l l e d t h e m e t a l i m i o n o r thermoclina occurs a t a depth of some 5 t o

15 m. I t s thickness v a r i e s and may even reach 6 m. This l a y e r i s c h a r a c t e r i z e d by a quick decrease i n water temperature with t h e depth, e x c e p t i o n a l l y reaching 8OC a t 0.3 m. (Fig. 4.18

T5e upper l a y e r , above t h e m e t a l i m i o n , is t h e epilimnion, where t h e e f f e c t s of s o l a r r a d i a t i o n a r e i n t e n s i v e , e s p e c i a l l y i n the sumer season. This l a y e r extends t o a depth of some 4 t o 15 m. I n t h i s l a y e r , t h e stock of oxyEen is supplunented from t h e atmosphere by d i f f u s i o n as w e l l a s by t h e photosynthesis of t h e water organisms. During the s u m e r season the water temperature of this upper l a y e r is h i g h e r , and i n w i n t e r larder, than the temperature of the lowest l a y e r , the hypolimnion. The temperature of t h e s u r f a c e of t h e epilimnion is decreased from t h e s u r f a c e by evaporation, thris causing an upward flow of water. The wind p r e s s u r e on t h e water s u r f a c e r e s u l t s i n a t u r b u l e n t flow, catisinp tog e t h e r with t h e water inflow from t r i b u t a r i e s a mixing of water and a downward t r a n s f e r of h e a t and k i n e t i c energy. The changes of water q u a l i t y may r e s u l t i n t h e c r e a t i o n of a c m p a r a t i v e l y h e a v i e r , c o o l e r l a y e r a t t h e r e s e r v o i r bottom, enriched by products from the m i n e r a l i z a t i o n and decomposition processes. The chemical composition of t h i s l a y e r causes t h i s water t o reach i t s h i g h e s t d e n s i t y a t a temperature s l i g h t l y above 4OC. This l a y e r , the monolimnion, mostly does n o t take part i n the process of water c i r c u l a t i o n . Jmcal c i r c u l a t i o n flows may occur i n any p a r t of the reservoir, b u t the overa l l c i r c u l a t i o n is a r e s u l t of the d e s t r u c t i o n of t h e balance which arises from

320 s t r a t i f i c a t i o n by e x t e r n a l forces. The p r o b a b i l i t y of the occurrence of an overturn i s , t h e r e f o r e , g r e a t e r a t the time of a non-marked s t r a t i f i c a t i o n . This time occurs mostly i n s p r i n g o r autumn, when the upper and lmer l a y e r s oE the r e s e r v o i r have the s m e temperature, i . e. during the pcriod of homothemicity (Fig. 4 . 1 9 ) . Such a s t a t e occllrs once o r s e v e r a l times during s p r i n g o r autumn. During these periods of s p r i n g and a\itumn c i r c u l a t i o n , the flow caused by the wind e f f e c t mixes the whole vollme of the r e s e r v o i r , mostly with t h e exception of t h e monolimnion.

300

0

0 4

3;

0

30°C

SPRING STAGNATION

HOMOTHER-

STAG NAT I ON

MlClTY

7

0

(:I

C

0.06 -

20

(mg. I-’)

0.f

0..2 0,3

,

100 200 300

I7 BENTHOS

20 (mg. 1-t)

Fig. 4.19. Seasonal changes i n thermal s t r a t i f i c a t i o n i n deep r e s e r v o i r s . Oxygen content and o t h e r q u a l i t y i n d i c a t o r s depend on depth and r e s e r v o i r operation (x). According t o Chen and Orlob (1980). I n s u m e r and a l s o during w i n t e r , when the r e s e r v o i r is not covered by ice, winds cause water c i r c u l a t i o n i n the l a y e r of the e p i l h i o n only. During these periods of s t a g n a t i o n , the h e a t balance of t h e r e s e r v o i r is influenced by the h e a t exchange between t h e b o t t a n and water and by the h e a t i n p u t o r output from the water l e v e l o r ice cover, i . e . n o t by o v e r a l l water c i r c u l a t i o n . The motion

of the suspended matter, t h e i r f l o a t i n g and sedimentation, depends on these

32 1 c i r c i i l a t i o n phenomena. I n s i i m e r w a t e r from t r i b i i t a r i e s , iisiially c o o l e r than the water i n the res e r v o i r , p e n e t r a t e s below t h e warn epilimnion, follovin,c the d i r e c t i o n of the o r i g i n a l r i v e r channel. Diirinp t h i s season the water t e w e r a t r i r e in a s i n g l e , deep man-made l a k e is comparatively h i g h e r than i t would be i n a n a t u r a l lake iinder the same topographical and c l i m a t o l o g i c a l c o t d i t i o n s . The outflow of the c o o l e r water frmi t h e hypolimnion through tiirbines i n a n i n c r e a s e i n t h e .average t m p e r a tiire

,2f

and bottom o i i t l e t s results

tt:e r e s e r v o i r .

Diiring w i n t e r , t h e bottmi o u t l e t s and turbines r e l e a s e water which i s warmer i n comparison w i t h the upper l n y p r s , r e s u l t i n g i n a decrease i n t h e water temper a t i i r e . The average water temperature of man-made lakes i s . diiring the winter season, t h e r e f o r e lower than t h a t of n a t u r a l lakes. F l m conditions r e s u l t i n g from t h e inflow of t r i b u t a r i e s a r e s i i b s t a n t i a l l y more complicated as CornFred with the simple p e n e t r a t i o n of the c o o l e r infloKbelow t h e equilibrium i n s u m e r . A f t e r the s p r i n a c i r c u l a t i o n a s u b s t a n t i a l l y l m e r flow occurs i n the r e s e r v o i r . The s i t i i a t i o n i s quite d i f f e r e n t i n a cascade of man-made lakes. The temperat u r e i n t h e second and f u r t h e r r e s e r v o i r s is g r e a t l y influenced by the i n p u t of

cool water from the iipper r e s e r v o i r . I t changes n o t only v e r t i c a l l y , biit a l s o i n the l o n g i t u d i n a l p r o f i l e . The average of t h i s temperatiire, and the temperature of the s u r f a c e l a y e r , is also lower than i t would be i n a n a t u r a l lake under si mi l ar conditions. The s u r f a c e temperatures and of ten also average temperatures reach t h e i r minimum i n summer j u s t damstream of the upper clam. The l o c a t i o n of a r a p i d inc r e a s e i n temperature, corresponding t o a drop of the streamline and the forrnat i o n of a n epilimnion, changes w i t h t h e values of inflow from the upper r e s e r v o i r . Increased discharges u p s e t the ups trearn zone of the metalimnion i n t h e d i r e c t i o n of the flow and extend the zone with low s u r f a c e temperatures, thus r e s t r i c t i n g the p o s s i b i l i t i e s of bathing. For s i m i l a r reasons, the s u r f a c e tern p e r a t u r e decreases i n t h e d i r e c t i o n of the main flow downstream of the upper reservoir. The q u a l i t y of water i n r e s e r v o i r s is determined by the i n t e r p l a v of

-

the water exchange r a t e ,

-

t h e q u a l i t y of water e n t e r i n p the r e s e r v o i r , the climate and weather,

-

-

-

the hours of sunshine, the r e s u l t i n g water temperature, the morphological c h a r a c t e r i s t i c s of t h e r e s e r v o i r , e s p e c i a l l y i t s depth, the m a t e r i a l of t h e r e s e r v o i r b o t t m , t h e a q u a t i c ecosystem and ecosystem of the surroundings the impact of human a c t i v i t i e s . The q u a l i t y of t h e water e n t e r i n g the r e s e r v o i r varies considerably with the

322 season, being considerably influenced i n dry periods by t h e qtiality of e f f l u e n t s from i n d u s t r i a l and a g r i c u l t u r a l e n t e r p r i s e s . I n a r i d c o u n t r i e s , the s a l i n i t y of t h e inflow may i n c r e a s e considerably i n t h i s period. I n high-flow periods, the q u a l i t y of t h e inflow depends t o a g r e a t e x t e n t on the erosion r a t e , i . e . on the m a t e r i a l of t h e riverbed and wash from ciiltivated and f e r t i l i z e d land, depending

on the season, a g r i c u l t u r a l p r a c t i c e s and on the r a i n f a l l i n t e n s i t y .

The s e l f - p u r i f i c a t i o n process i n r e s e r v o i r s with the exception of sedimentat i o n is negatively influenced by t h e g r e a t e r depth of water, r e s u l t i n g i n lower oxygen content and lower temperature i n canparison with the o r i g i n a l conditions of the riverbed. Reduced flow v e l o c i t i e s r e s u l t i n higher sedimentation with a lonp period of s e t t l i n g , hence reducing the t u r b i d i t y of water. The increased d e t e n t i o n time leads t o increased b i o l o g i c a l a c t i v i t y . A higher nitrogen content, e n t e r i n g the r e s e r v o i r mainly a s a r e s u l t of wrong c u l t i v a t i o n p r a c t i c e s , and higher s u r f a c e temperatures with slmer watcr flow i n the epilimnion r e s u l t i n the over-development of a l g a e . The decay of these organisms causes secondary p o l l u t i o n , decreasing the oxygen c o n t e n t , poisoning o t h e r organisms and d i s n i p t i n p t h e b i o l o g i c a l balance. Serious t r o u b l e may be caused by the over-development of weeds i n t h e shallow p a r t s of the r e s e r v o i r . ' h e t h e m 1 s t r a t i f i c a t i o n r e s u l t s i n t h e forma t i o n of zones of d i f f e r i n g water q u a l i t y (Fig. 4.19).

These zones d i f f e r not only chemically, but a l s o i n t h e

content of various water organisms and can be modelled mathematically (Fip.4.20). The hypolimnion may be, and the monolimnion c e r t a i n l y is characterized by anaerobic

conditions and high concentrations of iron Fe, manganese rln and s i l l -

phides; t h i s causes q u a l i t y deterioration, e s p e c i a l l y during the n a t u r a l autumn overturn o r during excessive water withdrawals. This d e t e r i o r a t i o n may occur a s a low level of dissolved oxygen, high Fe, 'ln and hydrogen siilphide concentration and i n o r g a n i c and inorganic tastes and odours. \ h e n a cool water input o r c i r c u l z t i o n does n o t destroy the n a t u r a l t h e m 1 s t r a t i f i c a t i o n , a decrease i n the oxygen content of the epilimnion occurs i n the

s m e r season. During t h a t period t h i s l a y e r l o s e s , w i n g t o c i r c u l a t i o n , up to

50% of the oxygen content acquired i n s p r i n p . The c h a r a c t e r of the biochemical changes i n the water q u a l i t y i n the e p i l i m nion depends mainly on the course and type of processes, e s p e c i a l l y those which occur i n the sumner season. Nutriments e n t e r the f r e e space of t h e r e s e r v o i r , a l s o from i t s bottom, by means of the c i r c u l a t i o n , thus c o n t r i b u t i n g t o the a c t i v a t i o n o f the b i o l o g i c a l process. Oxygen l o s s e s a r e balanced by t h e decrease i n temperature i n autumn. The hypolimnion, having no c o n t a c t with t h e atmosphere, loses i t s Oxygen content a s a r e s u l t of decomposition processes, which occur e s p e c i a l l y i n the bottom sediments, The decrease i n oxygen content may r e s u l t i n an oxygen d e f i c i t , and i n the decay of a e r o b i c organisms. The thermal s t r a t i f i c a t i o n influences a l l t h e

323

* INPUT General controls, System geometry, co e f f i c ient s WEATHER INFLOWS,

QUALITY

I

I

DEPOSITION OF INFLOWS CALCULATE VERTICAL ADVECTON

TEMPERATURE

Matrix

PROF I L E

Operation Module

L

CONS E RVAT I V E SUBSTANCES

I.

T D S , ALKALINITY

Form matrix coefficients

NO CONS ERVAT I V E SUBSTANCES

2 . S o l v e for *d/t t 3. Solve

c /t

+At/ for t a t /

4 . R e t u r n with new concent r a t ions NUTRIENTS P , N /NH3 NOZ,

,

NO/,

C

RES U LT S

Fig. 4.20. Flowchart diagram ( t h e lake ecological model) f o r determining the changes i n water q u a l i t y and the biomass production according t o Chen and Orlob (1973).

324 chemical and b i o l o g i c a l p r o c e s s e s , determining the w a t e r q u a l i t y and t h e r a t e of b i o l o g i c a l production (Fig. 4 . 2 0 ) . Human a c t i v i t i e s a l s o c o n t r i b u t e t o the occurrence of zones with an oxygen d e f i c i t , e s p e c i a l l y e f f l u e n t s , p i t s and dikes a t the bottom of the r e s e r v o i r , impeding the water c i r c u l a t i o n . S i m i l a r e f f e c t has the inexpediency of t h e res e r v o i r o p e r a t i o n , e . g . i t s emptying by upper o l i t l e t s and s p i l l w a y s , which i s required n o t only during floods but a l s o t o i n c r e a s e the water temperature i n

s m e r f o r b a t h i n g downs treams . The thermal s t r a t i f i c a t i o n is less s i p n i f i c a n t , o r does n o t occur a t a l l , i n

shallow r e s e r v o i r s (see Eq. 4.31). The c o o l e r water is g e n e r a l l y a t the end of the backwater. The temperature i n c r e a s e s i n t h e d i r e c t i o n of therrain flow, i . e . to the d a m , s p i l l w e i r o r o u t l e t . The h e a t i n e r t i a of shallow r e s e r v o i r s is low. The decrease i n temperature a t n i g h t may r e s u l t i n the f o r n i t i o n of homother-

m i c i t v , enabling i n t e n s i v e water c i r c u l a t i o n . The h i g h e r day temperatures r e s u l t i n the formation of an inexpressive metalimnion. A s i t grows i n s i z e , t h e m e t a l i m i o n reaches the bottom, and e r a d u a l l y disappears. The r e s i i l t i n p homothermicity permits freqiient c i r c u l a t i o n , thereby i n c r e a s i n g t h e b i o l o g i c a l production of shallow r e s e r v o i r s . An improvement i n water q u a l i t y i n r e s e r v o i r s can be achieved by mechanical d e s t r a t i f i c a t i o n , by t h e use of a i r and mechanical piimps o r by treatment with I

copper s u l p h a t e CriSO with o r without c i t r i c a c i d , lime and aliim. The c o n t r o l of 4 a l g a e g r m t h can a l s o be achieved by l i r n i t i n p t h e nutri-ent i n p u t i n t h e major t r i b u t a r i e s , e s p e c i a l l y by 1imit.ing t h e i n p u t of phosphonis.

4.6.4 I n f l u e n c e of Plan-made L.akes on t h e Riasphere and S o c i e t y ' h e development of aqiiatic l i f e i n a new r e s e r v o i r i s g r e a t l y influenced, and the water q u a l i t y i s determined, by t h e followinp f a c t o r s : - topographical, geological and s o i l c o n d i t i o n s of t h e l o c a l i t y and its vegeta t i v e canopy - c l i m a t o l o g i c a l conditions of t h e s i t e , e s p e c i a l l y t h e d u r a t i o n of sunshine - water q u a l i t y of i t s t r i b u t a r i e s and t h e r e s u l t i n g water temperature - the o r i g i n a l ecosystems i n t h e r i v e r and on t h e s h o r e

-

c l e a r i n g , removinp of stamps, l i t t e r , humus, c l e a n i n g and o t h e r measures

undertaken by man t o decrease s a n i t a r y hazards - measures taken by man t o a c c e l e r a t e t h e development of d e s i r a b l e s p e c i e s i n the ecosystem o f t h e new r e s e r v o i r

-

o p e r a t i o n ol t h e r e s e r v o i r , o f t e n causinp a p e r i o d i c d a i l y , weekly and sea-

sonal d r a w - d m and rise of t h e water t a b l e - a p p r o p r i a t e h u m n a c t i v i t i e s d u r i n g t h e r e s e r v o i r ' s o p e r a t i o n , namely those r e s u l t i n g i n water p o l l u t i o n . (Tab. 4.19).

325 TABLE 4.19 ~~

Category

Factor

Category

Factor

;{qua t i 2 :

Terres t r i a ! : P-pula t i o n

Crops 1Va::ml v e g e t a t i o n Herbivorous mammals Carnivorous mamals 1Jpland game b i r d s Predatory b i r d s

Habitat/land use

Bottmland f o r e s t ( a ) Ilpland f o r e s t 6) Dnen !non-forest)lands(c) Drawdown zonc TAnd u s e

Land qiiality! S o i l e r o s i o n s o i l e r o s i o n S o i l chemistry Mineral e x t r a c t i o n Species d i v e r s i t v C r it ica 1 ccmmuni ty r e l a t i o n sh i p s Air: hiality

Carbon monoxide Hydrocarbons Oxides of n i t r o g e n P a r t ici I 1a tes

Climatology

Diffusion f a c t o r

Hiunan Interface.

No;i e

Noise

Aesthetics

IhJidth and alignnimt Variety w i t h i n vegetation tyne Animals-domestic M a tive Fauna Appearance of water Odor and f l o a t i n g mterials Odor and v i s u a l q u a l i t y Sound

Historical

Internal & external s i t e s

P o p l a t ions

k t u r a l vegethtion Wet land Lrege t a t ion Zoopi an’:to? Phy torrla-+ton Sport f i s h Comercia 1 f i s h e r i e s I n t e r t i d a 1 rrgmisms SenthosjE-i br,n tlios Wat p r f ow 1

Flab i t a t s

Stream ( ~ 1 ) Freshiwter lsite ’e) ‘River Swamp ‘f) Non-river Swamp ‘P)

Water q u a l i t y PI! ievel. Tiirbiaity Silspended solids Water temperature Dissolved oxygen Biochemical oxygen demand Dissolved s o l i d s Inorganic n i t r o g e n Inorganic phosphate Salinity I r o n and mnganese Toxic substances Pesticides Faecal coliforms Stream a s s i m i l a t i v e ca pa c 1t y Water quantity

Stream flaw v a r i a t i o n Rasin hydrologic loss

Critical Species d i v e r s i t y community relationships

Archaeolopkal I n t e r n a l & e x t e r n a l s i t e s C h e c k l i s t of bio-physical and c u l t u r a l environment f a c t o r s f o r impoundment proj e c t s accordinp t o Canter (1983). E x p l i c a t i o n s f o l l m .

32 6 (a)

A composite of the species a s s o c i a t i o n s : percentage mast-bearinr

trees;

percentage cowred by imderstory; d i v e r s i t y of understory; percentage covered by groundcover: d i v e r s i t y of groiindcover : number of trees 2 0 . 5 m diameter per ha ; percentage of t r e e s 2 0.5 m diameter; frequency of inundation: edge (qriantity) and edge f q r i a l i t y ) . ( b ) A composite of t h e following: species a s s o c i a t i o n s ; percentage mstbearing t r e e s ; percentage coverage of understory; d i v e r s i t y of understory; per-

centage coverage of groundcover : d i v e r s i t y of groundcover; ntniber of t r e e s 0 . 5 m diameter/ha; percentage of trees 2 0 . 5 m diameter; q u a n t i t y of edqe; and, mean d i s t a n c e t o edge. ( c ) A composite of the following: land use: d i v e r s i t y of land use; quantity of edge; and, mean d i s t a n c e t o edge. (d) A composite of the followin?: s i n u o s i t y ; dominant centarchids; mean low water width; t u r b i d i t y ; t o t a l dissolved s o l i d s ; chemical type; d i v e r s i t y of f i s h e s ; and d i v e r s i t y of benthos. ( e ) A composite of the following mean depth: t u r b i d i t y ; t o t a l dissolved s o l i d s ; chemical type; shore development; spring flooding above veget.ation l i n e ; s t a n d i n e crop of f i s h ; standing crop of s p o r t f i s h ; d i v e r s i t y of f i s h ; , and, d i v e r s i t y of benthos. (f)

A composite of the followinR: species a s s o c i a t i o n s ; percentage f o r e s t

cover; percentage flooded annually; groundcover d i v e r s i t y ; percentage of groundcover; and, days s u b j e c t t o r i v e r overflow. (g)

A composite of t h e f o l l m i n g ; species a s s o c i a t i o n s ; percentage f o r e s t

cover; percentage flooded annually ; groiindcover d i v e r s i t y and percen tape o€ groundcover. Non-influenced ecosystems i n the man-made r e s e r v o i r tend i n the long term to achieve b i o l o g i c a l eqtJilibrillm, corresponding t o a n a t u r a l lake under s i m i l a r conditions. Man-made r e s e r v o i r s can t h e r e f o r e be cate,gurized i n t h e same way a s natural lakes (Tab. 1.31). As soon a s t h e f i l l i n g up of a r e s e r v o i r begins, the o r i g i n a l ecos!;stem

of

flowing r i v e r water changes, gradually being replaced by a new ecosystem of stagnant water. Within a period of several weeks, an overdevelopment of some plankton species usually oc.curs. This hoom a f f e c t s the s p e c i e s , h i c k do not encounter impol-tznt l i f e concurrence and f i r s t find t h e r i c h stock of nutriments i n t h e newly

flooded s o i l l a y e r s and t h e i r p a r t l y ranoved vegetation canopy.

The development boom of t h i s species is i n t e r r u p t e d i n t h e n e x t s t a g e by an overdraw of the o r i g i n a l nutriments, leading t o t h e development of o t h e r species. This s i t u a t i o n gradually tends towards a b i o l o g i c a l equilibrium, with a more r i c h a q u a t i c l i f e i n the area of the e s t u a r i a e s of the r e s e r v o i r t r i b u t a r i e s , where the nutriment i n p u t is more i n t e n s i v e .

327 The a q u a t i c l i f e of man-made lakes i s g r e a t l y influenced by a frequent d r a w darn and rise of the water l e v e l . This r e s u l t s i n the poorer heterogeneity of ecosytems i n the upper l i t t o r a l zones of man-made r e s e r v o i r s i n comparison with n a t u r a l ones: these ecosystems do n o t include species which a r e not r e s i s t a n t t o the

f l u c t u a t i o n of the water l e v e l and which c a m n t follow the water l e v e l

o r f i n d a temporary s h e l t e r i n the denuded s u r f a c e cover. This is the reason why a niunber of c u r r e n t species a r e disappearing a s a res u l t of the a c t i o n of the f l u c t u a t i n g water l e v e l , including weed, rush e t c . ,

and t h e r e only remain some unwanted species of i n s e c t s (some midges and m a t s ) and worms ( e . g . l e e c h e s ) . The occiirrence of m s q u i t o s can be s i g n i f i c a n t l y reduced by a managed draw-down and r i s i n g up of the water level.. The occurrence of aqiiatic species depends mainly on (a)

c r i t i c a l physical and chemical f a c t o r s , i . e . on the occurrence of n u t r i -

ments which are indispensable f o r t h e r e l e v a n t species i n q u a n t i t i e s exceeding the necessary minimum, (b)

the ecological valency, i . e . on the e x t e n t of the tolerance of the re-

l e v a n t organisms t o these f a c t o r s and t o t h e occurrence of o t h e r unwanted corn ponents of t h e i r l i v i n g environment. C r i t i c a l limits and optimum conditions a r e s p e c i f i c f o r the species i n qiiestion. Approaching these l i m i t s , l i v i n g phenomena become more demanding, e s p e c i a l l y e n e r g e t i c a l l y . I h d e r favourable conditions,

less energy i s required, leaving a q u a t i c aninals t h e necessary reserve f o r findi n g and consuming food. A s u f f i c i e n c y of food and energy supply and an appropriate environment form t h e optimum l i v i n g conditions f o r t h e species i n questivn.

lhe existence of r e l e v a n t f i s h species depends on the water q u a l i t y , - mainly ,on i t s temperatune and oxygen content, on t h e water depth, r a t e of flow, morphology and macerial of t h e bottom and the banks, and on t h e occurrence of

aquatic

f l o r a . The construction and operation of a r e s e r v o i r changes a l l these conditions.

A dam o r a weir fonns an i n v i n c i b l e o b s t a c l e f o r the draw of migratory f i s h e s , e . g . e e l s , salmon. Fish t r a p s , e l e v a t o r s and o t h e r equipment constructed t o enable the migration of f i s h e s do n o t form an adequate s u b s t i t u t e f o r such a purpose. There a r e a l s o problems with t h e optimum location of such equipment and t h e i r capacity, espec i a l l y i n t h e period of the draw, i s o f t e n n o t s u f f i c i e n t . The migration of f i s h e s is already r e s t r i c t e d during t h e construction period. The development of some f i s h species i s even c u r t a i l e d . Fish species t h a t a r e not ?ble t o accept the changed conditions d i e o u t , changing i n t h i s way the s t n i c t u r e of the ecosystem and conditions f o r the developmnt of o t h e r h e r b i w r e s , carnivores and d e t r i v o r e s . The conditions f o r f i s h occurrence i n fish-ponds d i f f e r completely from those

in r e s e r v o i r s used f o r water supply and flow c o n t r o l . High inflow and

outflow r e s u l t i n a high r a t e of water exchange and i n water q u a l i t y which i s characterized by a lack of nutriment content. Fresh water f i s h e s usually l i v e

328 n e a r s h o r e s , and n o t i n t h e f r e e space, where a l a c k o f n u t r i t i o n occurs. Tnls r e s u l t s , togei-her with the lack o f s o l a r r a d i a t i o n , low temperature and lack of oxygen, i n a s u b s t a n t i a l drop i n p r o d u c t i v i t y i n r e s e r v o i r s deeper than f i f t e e n meters. The water l e v e l f l u c t u a t i o n reduces t h e production s u r f a c e and destroys zooplankton, t h e b a s i c component of t h e f i s h e s ' food. Tne p r o d u c t i v i t y of a reserv o i r does n o t depend on t h e extend and frequency of t h e water l e v e l f l ~ i c t u a t i o n o n l y , b u t also on t h e p e r i o d of i t s occurrence. Shores covered by a dense veget a t i v p canopy form favourable conditions f o r f i s h s h e l t e r s , spawn deposition and f o e t u s development. The decrease i n t h e water l e v e l iisually d e s t r o y s spawn and foetiis, e s p e c i a l l y i n i t s e a r l y s t a g e of development. The drop i n t h e water t a b l e a l s o has c e r t a i n p o s i t i v e e f f e c t s on f i s h production, fomiinp s u i t a b l e conditions f o r fauna development i n t h e uncovered s u r f a c e . The inundated g r a s s e s c r e a t e a favourable environment f o r t h e development o f some f i s h s p e c i e s , a s w e l l a s o f f e r i n g them food. The population boom of some f i s h s p e c i e s , e . g . of p i k e , a f t e r the f i r s t f i l l ing of t h e r e s e r v o i r i s also caused by t h e abundance of nutriments i n the newly inundated s o i l s u r f a c e and by t h e number of s h e l t e r s . This population boom l a s t s s e v e r a l y e a r s , then g r a d u a l l y

diminishes.

Ichthyofauna o f man-made lakes can be categorized a s follows: ( a ) f i s h e s which occur i n t h e r e s e r v o i r from t h e o r i g i n a l ecosystem of t h e stream and which a r e a b l e t o adapt t o t h e changed environment and breed n a t u r a l l y , h ) fishes

which have extremely favoiirable conditions f o r t h e i r natiiral

breeding and development and a r e a b l e t o exterminate o t h e r f i s h s p e c i e s ,

(c\

f i s h e s of t h e o r i g i n a l ecosystem which a r e a b l e t o adapt to t h e changed

conditions only i n r e s t r i c t e d a r e a s of stream e s t u a r i e s , where conditions have not been changed d r a s t i c a 1l y , ( d ) f i s h e s which a r e a b l e t o l i v e i n the reservoir, b u t do r:ot have the abil i t y t o breed n a t u r a l l y , thiis r e q u i r i n g a r t i f i c i a l breeding f o r replenishment of t h e i r occurrence, ( e ) f i s h e s which a r e imported a r t i f i c i a l l y from o t h e r ecosystems and, being adaptable t o t h e r e s e r v o i r c o n d i t i o n s , a r e a b l e t o f u l f i l l t h e required function i n t h e r e s e r v o i r ecosys t e m : weed r e d u c t i o n , maintenance of ecosystem equilibrium,

meat production e t c . The ecosystem of a r e s e r v o i r includes (a)

f i s h e s intended f o r breeding,

'b) supplementary f i s h e s , u s i n g food which i s n o t u t i l i z e d by t h e r a i s e d fishps. The e x t e n t and i n t e n s i t y of changes i n t h e landscape caused by t h e r e s e r v o i r depend n o t only on t h e topography, c h a r a c t e r and a c c e s s i b i l i t y o f t h e a r e a and

on t h e d e n s i t y of popillation and communication l i n e s , b u t a l s o

OR

t h e s i z e of the

329 r e s e r v o i r , e s p e c i a l l y on i t s s u r f a c e a r e a . The following occurs a f t e r the const r u c t i o n and o p e r a t i o n of a r e s e r v o i r : (a\

-

changes i n t h e inundated a r e a :

flooding o f f o r e s t s , c r i l t i v a t e d and urbanized l a n d , comnunications, b u i l d i n g s

and o t h e r engineerinE works, landmarks and h i s t o r i c p l a c e s , - flooding of mines and mineral d e p o s i t s e t c . ,

-

t h e e x t i n c t i o n of t h e o r i g i n a l ecosystems, t h e d e s t r u c t i o n of dry land species

of f l o r a and fauna, i n c l u d i n g t h e r a r e ones, -

t h e i n c e p t i o n of a q u a t i c

f l o r a and fauna, a s w e l l as t h e extension and chanEe

of i t s environment, i n c l u d i n g t h a t f o r fowl and i n s e c t s .

-

Ib) changes i n t h e r e s e r v o i r environment c r e a t i o n of new scenery, influenced by the water l e v e l f l u c t u a t i o n ,

- changes i n t h e hydrogeological and hydropedological c o n d i t i o n s , new b a l l a s t of t h e E a r t h ' s c r i i s t ,

-

changes i n t h e groundwater l e v e l , s o i l misture and a i r hiunidity, changes i n

tempera tiire, r e s u l t i n g i n a change of ecosys tems ,

-

chanzes i n the l i v i n g environment o f man: change i n dwelling environment, i n

h e a l t h and r e c r e a t i o n a l c o n d i t i o n s , and a s e v e r i n g of comnunication l i n e s , - change i n t h e conditions f o r economic development: t h e economic impact of the dam c o n s t r u c t i o n and r e s e r v o i r o p e r a t i o n causes a c o n s t r u c t i o n boom, a s t h e equipment used on t h e b u i l d i n g s i t e o f f e r s p o s s i b i l i t i e s f o r f u r t h e r u t i l i z a t i o n , and t h e c o n s t r u c t i o n of new comnunications i n c r e a s e s t h e a c c e s s i b i l i t y of t h e a r e a and i t s consequent u t i l i z a t i o n f o r r e c r e a t i o n purposes, which leads t o a modernization of t h e l i f e s t y l e of t h e population. The r e s e r v o i r ' s environment i s n e g a t i v e l y a f f e c t e d by t h e water l e v e l fluct u a t i o n , e s p e c i a l l y a t t h e end of backwater and i n f l a t a r e a s . When t h e banks a r e s t e e p , l a n d s l i d i n g may occur. The n e g a t i v e consequences o f t h e w a t e r l e v e l f l i i c t u a t i o n should be r e s t r i c t e d by overflow dams, d i k e s , banks, ramparts, and by excavation i n shallow flooded a r e a s e t c .

D r y land ecosystans a r e a f f e c t e d n o t only by t h e r i s e i n t h e groundwater l e v e l and by an i n c r e a s e i n s o i l moisture 2nd a i r humidity, but a l s o by t h e flooding of p a s t u r e s and dens, by complications a s s o c i a t e d with t h e access of shy animals t o water, by t h e worsening i n t h e l i v i n g c o n d i t i o n s , e s p e c i a l l y of r a r e spec i e s , through t h e i n c r e a s e i n population d e n s i t y and economic a c t i d t i e s . Ln s p a r s e l y populated a r e a s r e s e r v o i r shores form favourable conditions f o r n e s t i n g and r e s t i n g p l a c e s f o r migratory b i r d s . The s o c i a l , group and personal i n t e r e s t s of t h e population a r e a f f e c t e d by the c r e a t i o n o f new s h o r e s , by t h e i n c r e a s e i n s o i l m i s t u r e , by changes i n the microclimate e t c . The i n c r e a s e i n dwelling value of a r e a s n o t adversely a f f e c t e d by water l e v e l f l u c t u a t i o n waterlogging o r o t h e r n e g a t i v e e f f e c t s r e s u l t s i n an i n c r e a s e d d e n s i t y of h a b i t a t i o n . The change i n the dwelling value has an i m p o r

330 t a n t impact on the l i f e s t y l e , supporting i t s r e c r e a t i o n a l a s p e c t s . The reserv o i r c r e a t e s o r supports favourable conditions f o r f i s h i n g , camping, hunting, and o t h e r types of

veelrend and vacational r e c r e a t i o n . The space f o r water t o u r

i n c r e a s e s , but the r e c r e a t i o n a l value is sometimes prejudiced by the change

ism

of the flowing water i n t o s t a g n a n t water. The increased d e n s i t y of h a b i t a t i o n has a s a secondary e f f e c t a breaking down of t h e n a t u r a l v e g e t a t i v e canopy, an i n c r e a s e i n the erosion r a t e . a rise i n the t r a n s p o r t d c n s i t y , an increase i n n o i s e d e n s i t y , a gradual p o l l u t i o n of the environment, with t h e

concomitant need f o r a mass water supply, orEanized waste

and waste water removal. Depending on t h e water q u a l i t y and p r e v a i l i n g s a n i t a r y conditions, the reserv o i r operation can c r e a t e o r strengthen the conditions f o r t h e dissemination of germs o r th&

b e a r e r s , e s e p c i a l l y i n t r o p i c a l and s u b t r o p i c a l a r e a s . Negative

circiimstances may resiil t i n economic, cul tiiral and s o c i a l l o s s e s , e i t h e r permanent o r temporary, e s p e c i a l l y i n the period during and s h o r t l y a f t e r the cons-

true t i o n . Some of t h e expected economic e f f e c t s nay be not achieved due t o v a r i o i s planning, f i n a n c i a l and organizational obstacles o r due t o t h e unexpected react i o n of the population. This ,nainly concerns the immediate surroundings of the r e s e r v o i r , which sometimes f a i l t o a t t r a c t s u f f i c i e n t i n t e r e s t among p o t e n t i a l investors. [Jncoordinated planning and lack of investment i n f u r t h e r Construction acciviw o r i n s t i t u t i o n a l gaps may cause discrepencies i n t h e area i n question, r e s t r i c t i r l g o r even c a n c e l l i n g t h e p o s i t i v e impact of t h e r e s e r v o i r i n t h e border a r e a s , o r even a l t o g e t h e r .

4.6.5

E f f e c t of Flow Control and Water Withdrawals

Downstream of t h e dam p r o f i l e the r e s e r v o i r operation and water withdrawals affect, especially, - the water and i c e regime, the t r a n s p o r t of sediments, and t h e water q u a l i t y , - the a q u a t i c f l o r a and t h e r i v e r s i d e canopy, - t h e a q u a t i c fauna including f i s h e s ,

-

the dwelling value of t h e relevant a r e a (Tab. 4.20). Changes i n the water regime a r e m n i f e s t a t e d mainly by changes i n discharges,

dependent on t h e r e s e r v o i r operation, and on the t i m e d i s t r i b u t i o n of water withdrawals and e f f l u e n t s . These changes r e s u l t e s p e c i a l l y i n ( a ) a d e c l i n e i n peak discharges and r e l e v a n t water l e v e l s downstream, usually with t h e exception of superfloods and floods of long d u r a t i o n , because these o f t e n exceed t h e capacity of t h e r e s e r v o i r , (b)

an increase i n low discharges,

(c)

a water deficiency i n the case of excessive water withdrawls.

33 I TABLE 4.20

Impact o f r e s e r v o i r o p e r a t i o n and water withdrawl on downstream water course \dater q u a n t i t y

[dater q u a l i t y

Flora/Fishes Change i n water t a b l e and groundwater t a b l e

h e 1l i n g

Decrease i n hi&er discharges

Increase i n low discharges

Ilecrease i n Decreased sediment salinity transport of low discharges

Restricted floodinp

Improved water supply

Oecrease water t a b l e o f floods

I n c r e a s e i n Chanze i n salinity.by aquatic evaporation f l o r a

Improved flood control

Restricted natural fertilization

Improved navigation and power generation

Decrease i n sedimentat i o n flooded land

Increase i n nitrogen, i r o n and mangan content

Restricted s o i l regenera t i o n

Restricted erosion

Decrease i n sedimentation Decrease i n oxygen content

Increase i n yield

Changes i n p a t t e r n of wa tertourism

Restricted groundwater recharge

I n c r e a s e i n Decrease i n Decrease i n water tani n f i l t r a t i o n clogging perature i n summer

Interrupted draw o f , fishes

Restricted sumner recreation

Restricted waste disposal

Improved sanitary conditions

Increase i n Water tanperature i n winter

Restricted migration O f fishes

Restricted skating i n winter

Decrease.in evaporation

Slight increase i n evaporation

Change i n i n c e format i o n and

Change i n zones of fish occurrence

Extended period o f high turbidity

flow

Change i n coastal

flora

Decrease i n water t a b l e and d i s c h a r g e f l u c t u a t i o n P e r i o d i c f l u c t u a t i o n of water t a b l e and discharges i n c a s e of hydropower genera t i o n C h e c k l i s t o f t h e probable impact o f reservoir o p e r a t i o n and water withdrawal on downs tream water course.

332 Water withdrawals do n o t g e n e r a l l y r e s u l t i n a s i i b s t a n t i a l d e c r e a s e i n flood

d i s c h a r g e s , a s they a r e u s u a l l y comparatively s m a l l . Big withdrawals, such a s those used f o r i r r i g a t i o n purposes, reduce t h e value o f low discharges i n t h e siimer season, thus causing a n i n c r e a s e i n t h e s e discharges i n t h e w i n t e r season

on account o f t h e g r e a t e r groundwater oiitflow from i r r i m t e d land a t t h a t t i m e . I r r i g a t i o n may a l s o i n c r e a s e flood d i s c h a r g e s , because watered land has a l i m i ted i n f i l t r a t i o n c a p a c i t y , thus causinq a n i n t e n s i v e outflow of t h e rainwater. The flood c o n t r o l e f f e c t of the r e s e r v o i r r e s u l t s i n fa, (b,

a d e c l i n e i n t h e flooded a r e a , a d e c l i n e i n t h e e x t e n t and frequency of i r r i g a t i o n by flood water sprea-

d i n g and s o i l regeneration by s i l t sediments, (c)

a d e c l i n e i n t h e r a t e of n a t u r a l r i v e r s i d e i n f i l t r a t i o n ,

( d ) a d e c l i n e i n t h e e r o s i o n r a t e , and a n i n c r e a s e i n t n e sedimentation r a t e . The d e c l i n e i n t h e flooded a r e a r e s u l t s i n a reduction i n flood l o s s e s . N e v e r t h e l e s s , i r r i g a t i o n by flood water spreading i s r e s t r i c t e d , thus reducing t h e r e g e n e r a t i o n r a t e of t h e s o i l p r o f i l e . I n t h i s c a s e , t h e n a t u r a l watering and s o i l r e g e n e r a t i o n process has t o be replaced by a r t i f i c i a l i r r i g a t i o n and f e r tilizing,

which r e s u l t s i n high

o p e r a t i o n c o s t s and a l s o r e q u i r e s a p p r o p r i a t e

o p e r a t i o n s k i l l , a s w e l l as being connected with a change i n i r r i p a t i o n methods and i n t h e cropping p a t t e r n . The necessary measiires f o r t h i s purpose require the supply o f a r t i f i c i a l f e r t i l i z e r s , energy f o r t h e i r production, manpower and s k i l l and may appear t o be o p e r a t i o n a l l y , f i n a n c i a l l y o r o r g a n i z a t i o n a l l y rinsiritable, e s p e c i a l l y i n develop i n g c o u n t i r e s . They are f e a s i b l e f.sr i n t e n s i v e production, but a r e n o t satisf a c t o r y from t h e environmental p o i n t of view, a s they m y supply t h e requested q u a n t i t y o f anorganic n u t r i m e n t s , b u t n o t t h e necessary volume of organic m t t e r . Flood c o n t r o l r e s u l t s i n t h e d e c l i n e i n t h e n s t u r a l r i v e r s i d e i n f i l t r a t i o n , r.ediiction i n t h e groundwater recharge and subsequent n e g a t i v e influerice on a g r i c u l t u r a l production, e s p e c i a l l y i n f l a t r i v e r v a l l e y s . I n the case of the low q u a l i t y of r i v e r w a t e r , t h e drop i n t h e i n f i l t r a t i o n r a t e r e s u l t s i n an improvement of t h e groundwater q u a l i t y . The d e c l i n e i n t h e e r o s i o n r a t e and i n t e r r u p t i n g of t h e sediment t r a n s p o r t which r e s u l t from t h e flood c o n t r o l functions

of t h e reservoir serve the m i n -

tenance of r i v e r b e d s . As a consequence o f the r e d u c t i o n i n high d i s c h a r g e s , a n i n c r e a s e i n t h e sedimentation r a t e may occur r e s u l t i n g i n a decrease i n t h e channel c a p a c i t y downstream of t h e dam p r o f i l e and thus i n f l u e n c i n g water l e v e l hydrographs, n a v i g a t i o n conditions e t c . As a r e s u l t of the decreased discharges and a t t e n d a n t h i g h e r sedimentation, the rate of t h e s e l f - p u r i f i c a t i o n processes f a l l s , thus causing a d e t e r i o r a t i o n i n t h e water q u s l i t y . The decrease i n the e r o s i o n , and i n c r e a s e i n t h e sedimentation r a t e n e g a t i v e l y i n f l u e n c e t h e r r e n c e of f i s h s h e l t e r s , thus l i m i t i n g t h e f i s h population.

OCCII-

333 Depending on the given c o n d i t i o n s , the r e s e r v o i r with a low impact on flood discharges m y on the c o n t r a r y , owing t o i t s t r a p e f f i c i e n c y d e p r i v i n e the downstream flow of i t s sediment content, increase t h e erosion r a t e downstream. The increase i n low discharges i s caused not only by the r e s e r v o i r operation, but a l s o by the influence of water u t i l i z a t i o n processes between the water withdrawal and e f f l u e n t , the second process having a negative e f f e c t on the water qua 1i ty . The i n c r e a s e i n low discharges, being accompanied by a r a i s i n g of minimum

water l e v e l s , c r e a t e s more favourable conditions f o r water withdrawals, navigat i o n and water power generation, a s w e l l a s having a favourable impact on the groundwater regime, and therefore a l s o on a g r i c u ~ t u r eand f o r e s t r y . such a r a i s ing of the water t a b l e m y sometimes r e s u l t i n advancing p e r c o l a t i o n and evapor a t i o n , i . e . i n growing water l o s s e s . The flow r a t e i n c r e a s e s , a u p e n t i n g sediment

t r a n s p o r t and t h e r a t e of s e l f - p u r i f i c a t i o n processes, and thereby improv-

i n g the s a n i t a r y conditions and the a e s t h e t i c value. TJnder c e r t a i n circumstances the flow r a t e may exceed the relevant l i m i t i n g values of the r i v e r bottom stab i l i t y , thus causinz erosion. \dater w i thdr;wals t r a t i o n of

and subseqijent u t i l i z a t i o n frequently increase the concen-

dissolved o r susperided w t t e r i n t h e remaining discnarges. Water

u t i l i z a t i o n decreases the oxygen content e s p e c i a l l y and increases the nitrogen content. The r e g u l a t i n g e f f e c t of t h e r e s e r v o i r with a longer : r a t e of water exchange mostly reduces the l e v e l of water p o l l u t i o n . The a u p e n t a t i o n of low discharges a l s o d i l u t e s the p o l l u t i o n i n water from t r i b u t a r i e s and e f f l u e n t s . The sedimentation and s e l f - p u r i f i c a t i o n processes i n the r e s e r v o i r generally have a favourable e f f e c t on t h e q u a l i t y of t h e water outflow, even i n the case of a low q u a l i t y

inflow. I n semi-arid and a r i d a r e a s t h e concentration of

dissolved and suspended matter can nevertheless be increased by passing through the r e s e r v o i r with a high evaporation r a t e . The value of t h e water p o l l u t i o n downstream of the r e s e r v o i r , a t the conf1.uence o r a t t h e e s t u a r y of e f f l u e n t s , can be determined o r its course m d e l l e d on the b a s i s of the mixing formula

i

q l ' ici

iq i

3

-

',-

the concentration of r e l e v a n t i n d i c a t o r s before the confluence o r before the estuary of e f f l u e n t r e s u l t i n g concentration downstream

r e s u l t i n g concentration downstream

- l , 2 , 3

Q1 - Q,

.....,n

order of water q u a l i t y i n d i c a t o r s

- discharges upstream of t h e confluence.

The r e a l course of t h e water p o l l u t i o n i n t h e longitudina1 p r o f i l e of t h e

water course d i f f e r s from t h e computed on account of t h e s e l f - p u r i f i c a t i o n '

process incluclim sedimentation. The r e l e v a n t computed values should, t h e r e f o r e , be checked and c o r r e c t e d i n t h e seqiience from t h e upper p r o f i l e t o t h e e s t u a r y . On t h i s b a s i s , t h e course of t h e water q u a l i t y can a l s o be c o n t r o l l e d and i t s

improvement during c r i t i c a l p e r i o d s achieved by r e s e r v o i r o p e r a t i o n . Such an emptying o f t h e s t o r a g e is t o t h e detriment of t h e water supply. The f e a s i b i l i t y o f such o p e r a t i o n depends on t h e course of t h e decomposition processes and on the evaporation r a t e i n t h e r e s e r v o i r , and r e s u l t i n g w a t e r q u a l i t y . The changes i n water temperature dowristream o f t h e dam s i t e a r i s e froin t h e r e s e r v o i r o p e r a t i o n . With t h e power g e n e r a t i o n o r w i t h t h e bottom o u t l e t open, t h e deep water l a y e r s , i . e . t h e hypolimnion, a r e emptied, which r e s u l t s i n a cooling of the r i v e r water i n t h e summer season and i t s warming durinp w i n t e r , i n comparison with t h e o r i g i n z l s t a t e bpfore t h e r e s e r v o i r o p e r a t i o n . This water a l s o contains more n i t r o g e n and i r o n and less oxypen. The d i f f e r e n c e i n water q u a l i t y , i n c l u d i n g temperature, i s s u b s t a n i o n a l , e s p e c i a l l y i n t h e case of a cascade of r e s e r v o i r s . The water of the epilimnion, whose temperature does not d i f f e r as much from t h e o r i g i n a l one, e n t e r s t h e r i v e r channel downstream of the r e s e r v o i r by means of s p i l l w a y s ,

mainly during f l o o d s , i . e . not so f r e q u e n t l y .

Temperature changes have a n i n f l u e n c e on, e s p e c i a l l y , la)

water i i t i l i z a t i o n a f t e r its withdrawal

(b)

f i s h occiirrence and f i s h breedinp

Cc) o t h e r in-stream water u s e s , e s p e c i a l l y water s p o r t s , r e c r e a t i o n , navig a t i o n , and a l s o waste d i s p o s a l . The decrease i n water temperature i s f a w u r a b l e f o r both municipal and indust r i a l w a t e r siipply, namely f o r cooling purposes. For i r r i g a t i o n purposes, warmer water i s more convenient. Changes i n water temperature and water q i i a l i t y a l s o i n f l u e n c e t h e ichthyofauna. They may cause a change i n the zones of f i s h occurrence. The changes i n w a t e r temperature mostlv have a n e g a t i v e e f f e c t on rec r e a t i o n and water s p o r t s ; the cool water i n simmer s p o i l s the conditions f o r b a t h i n g and o t h e r water s p o r t s ; w h i l e t h e i n c r e a s e i n w i n t e r temperature rest r i c t s t h e f r e e z i n g o f t h e water pool and s k a t i n g i n w i n t e r , b u t tempers t h e i c e bound regime, thus c r e a t i n g more favourable conditions f o r water t r a n s p o r t . Water temperatures are a l s o a f f e c t e d d i r e c t l y by water withdrawals, decreasing w a t e r d i s c h a r g e s , w a t e r depth and flaw r a t e s with consequent temperature i n c r e a s e , a l s o caused by t h e high temperature of e f f l u e n t s from cooling systems. These temperature changes depend t o a g r e a t e x t e n t on t h e r a t i o of discharges and withd r a w a l s a n d o n t h e q u a n t i t y and temperature of e f f l u e n t s . Water withdrawals a l s o i n c r e a s e t h e c o n c e n t r a t i o n of sediments i n t h e remaining discharge, aggravated by material i n p u t from e f f l u e n t s , i n c r e a s i n g t h e sedimentation r a t e and causing the f i l l i n g o f r i v e r b e d s .

335 The drop i n t h e sediment content i n discharges caiised by the sedimentation i n the r e s e r v o i r reduces the course of water l e v e l s i n comparison with t h e s t a t e prior

LO

the r e s e r v o i r o p e r a t i o n . The f a l l i n t h e water t a b l e reduces t h e poten-

t i a l energy, and augments the k i n e t i c energy of water. This i n t e n s i f i e s t h e eros i o n p r o c e s s , e n t a i l i n g a g r a d m l i n c r e a s e i n sediment and bed-load t r a n s p o r t downstream, where, depending on t h e c o n d i t i o n s , t h e water l e v e l may gradually approach t h e o r i g i n a l one of the same discharge. Downstream of t h e r e s e r v o i r , the p e r i o d of t u r b i d water discharges i s u s u a l l y longer because of t h e g e n t l e sedimentation of f i n e p a r t i c l e s i n t h e r e s e r v o i r . The n a t u r a l r i v e r channel downstream of t h e r e s e r v o i r i s a l s o a f f e c t e d by the c o n s t r u c t i o n o f many o f f t a k e and o u t l e t s t r u c t u r e s , sane s t r e t c h e s being regulated o r paved i n t h i s connection. The n a t u r a l r i v e r s i d e canopy, whose development and s t a t e depends on c l i m a t o l o g i c a l conditions , a l t i t u d e , s o i l and geomorphologic a l c o n d i t i o n s , bank s l o p e s ,

e x p o s i t i o n o f t h e l o c a t i o n and the water regime

changes under t h e long-term i n f l u e n c e of t h e w a t e r l e v e l a l t e r a t i o n s and conseqiient changes i n groundwater t a b l e . Vegetation s p e c i e s which a r e n o t adaptable

t o t h e new c o n d i t i o n s gradually e x p i r e , a f f e c t i n g t h e scenery and t h e r e l e v a n t dwelling and r e c r e a t i o n a l c o n d i t i o n s . The l i v i n g conditions f o r f i s h e s i n t h e s t r e t c h which i s a f f e c t e d by the oper a t i o n of t h e r e s e r v o i r and e s p e c i a l l y by

-

chanpes i n water q u a l i t y , i n c l u d i n g temperatiire i n c r e a s e i n t h e minimum and decrease i n t h e maximum flood discharges and t h e i r

occurrence, - changes i n t h e r i v e r b e d and a s s o c i a t e d f l o r a , - c o n s t r u c t i o n of o b s t a c l e s f o r the movement o f f i s h e s upstream, a r e d r a s t i c a l l y changed. Thpse consequences include a decrease i n the tieterog e n e i t y of t h e p r e v a i l i n g ecosystems, i n c l u d i n g t h e e x p i r i n g o f migratory f i s h e s . The improvement of t h e water q u a l i t y and t h e decrease i n water temperature may r e s u l t i n t h e formation of a t r o u t zone i n t h e s t r e t c h downstream of t h e dam s i t e . I n t e n s i v e s p o r t f i s h i n g is o f t e n recorded i n t h e s e s t r e t c h e s , e s p e c i a l l y when t h i s a c t i v i t y is n o t permitted on t h e r e s e r w i r , e . g . because i t s water i s used f o r d r i n k i n g purposes. The flood c o n t r o l , water supply o r multi-purpose e f f e c t o f t h e r e s e r v o i r

o p e r a t i o n i n c r e a s e s t h e dwelling value o f t h e a f f e c t e d a r e a . Rut, downstream of the r e s e r v o i r , t h e r e o b t a i n s t h e r i s k o f a p o s s i b l e dam d e s t r u c t i o n . The probab i l i t y of such an event i s very low, b u t i t s consequences may be c a t a s t r o p h i c , d e s t r o y i n g economic values and t h r e a t e n i n g the population. The e f f e c t s of very l a r g e r e s e r v o i r s appear even a s f a r down as t h e e s t u a r y of t h e r i v e r i n t o t h e s e a , o r where i t e x p i r e s i n an a r e a without outflow. The drop i n t h e nutriment i n p u t and p o s s i b l e d e t e r i o r a t i o n i n water q u a l i t y by h w n a c t i v i t y m y l i m i t t h e e x t e n t and h e t e r o g e n e i t y o f the q u a t i c fauna including

336 f i s h e s , as w e l l as r e s t r i c t i n g f i s h prodiiction i n the c o a s t a l zone. The decrease i n sediment t r a n s p o r t may r e s u l t i n e r o s i o n , deepening t h e e s t u a r y and aggrav a t i n g sea-wave a c t i o n . The decrease i n discharges caused by t h e r e s e r v o i r o p e r a t i o n o r by water withdrawals r e s u l t s i n a n i n c r e a s e d p e n e t r a t i o n o f seawater upstream, w i t 6 a consequent i n c r e a s e i n s o i l s a l i n i t y , a l s o l e a d i n g t o a degradation of s a l t - r e s i s t e n t p l a n t s p e c i e s i n c l u d i n p e . g . d a t e palms. The s a l i n e e f f l u e n t s from i r r i g a t i o n schemes m y a l s o c o n t r i b u t e to t h i s degradation, a process which is more evident i n t h e dry period of low r i v e r discharges. ' h e r e s u l t i n g s t a g e i n the e s t u a r y l a r g e l y depends on the o p e r a t i o n both of

the r e s e r v o i r and t h e a s s o c i a t e d water users, The i n c r e a s e i n 1m discharges may cause a decrease i n t h e average s a l i n i t y , i . e . i t may shorter1 the period of upstream p e n e t r a t i o n of t h e s a l t y back w a t e r , which reduces t h e acreage of t h e a f f e c t e d a r e a . Another consequence may be t h e r a i s i n g of t r a c t i n g f o r c e s , and t h e i n t e n s i f i c a t i o n of t h e s e l f - p u r i f i c a t i o n p r o c e s s . I n t h i s way, a balanced r e s e r v o i r o p e r a t i o n can a l s o improve t h e conditions f o r c o a s t a l f l o r a , thereby augmenting

4.6.6

both a g r i c u l t u r a l and f i s h production.

E f f e c t of River T r a i n i n g and Open Channel Water Conveyance

The formation of r i v e r b e d s depends on hydrometeorologicel, hydrogeological, geomorphological and s o i l c o n d i t i o n s . I t i s a l s o a f f e c t e d by t h e occiirrence and s p e c i e s of t h e v e g e t a t i v e canopy

011

t h e r i v e r banks. The b a s i c n a t u r a l functions

of streams c o n s i s t o f (a)

drainape and water conveyance

(b)

i c e t r a n s p o r t during t h e w i n t e r and s p r i n g season,

Cc)

sediment and bed-load t r a n s p o r t , s o i l q u a l i t y r e g e n e r a t i o n ,

( d ) groundwater t a b l e and s o i l moisture r e g u l a t i o n , i . e . maintenance of cond i t i o n s f o r the r i v e r s i d e vegetation, ( e ) maintenance of c o n d i t i o n s f o r a q u a t i c l i f e and of envi.ronmenta1 balance. I n c i d e n t a l phenomena of t h e s e n a t u r a l f u n c t i o n s , such as floods, r e s t r i c t the p o s s i b i l i t i e s of u t i l i z i n g the a d j a c e n t a r e a f o r t h e various a c t i v i t i e s of human s o c i e t y , e . g . f o r i n t e n s i v e s e t t l e m e n t , i n d u s t r i a l and i n t e n s i v e a g r i c u l t u r a l prodtiction, mining, u n i n t e r n i p t e d in-stream water u t i l i z a t i o n e.g. navigation and water power g e n e r a t i o n . The v a r i a b i l i t v of t h e channels of n a t u r a l water c o u r s e s , t h e i r f l u c t u a t i n g water l e v e l s , changinE discharges and a l s o i c e phenomena n e g a t i v e l y i n f l u e n c e t h e socioeconomic fiinctions of w a t e r . For t h i s reason water courses a r e t r a i n e d and c a n a l s f o r water conveyance constnicted with t h e aim o f ( a ) improving t h e conditions of water supply and drainage, in-stream and on-side water u s e , (b)

r e s t r i c t i n g inundations and conseqiient economic l o s s e s ,

337 ( c ) adapting t h e r i v e r b e d t o t h e changing d i s c h a r g e s , inland water t r a n s p o r t requirements, power genera t i o n , sediment t r a n s p o r t o r ice regime phenomena, (d)

increasin,q t h e dwelling value o f the a d j a c e n t a r e a , s t a b i l i z i n g t h e r i v e r banks and r i v e r bottom, achieving d i r e c t i o n a l

(e) s t a b i l i z a t i o n , r e s t r i c t i n g t h e e r o s i o n process and removing i t s consequences, (f)

improving t h e groundwater regime,

(g)

adapting the riverbed t o t h e consequences of d i v e r s i o n dams and weir

c o n s t r u c t i o n , as w e l l as of the c o n s t r u c t i o n of comnunication l i n e s , urban, indirs t r i a l and a g r i c i i l t i i r a l development, (h)

improvinp t h e water q i i a l i t y , safemiarding t h e d e s i r e d s a n i t a r y conditions

and t h e requirements o f a e a t h e t i c enjoymentlTab. 4 . 2 1 ) . The

unavoidable

precondition f o r ensuring the d e s i r a b l e e f f e c t of r i v e r

t r a i n i n g i s t h a t n a t u r a l fimctions of t h e stream mustnot come i n t o c o n f l i c t with t h e d e s i r e d goals. The flow of n a t u r a l r i v e r s and streams is f r e q u e n t l y almost s t e a d y , i . e . changes very slowly with time. Tlnsteady flow occiirs as flood waves o r t r a v e l l i n e siirges. In natiiral r i v e r b e d s , t h i s flow i s non-uniform,

changing

slowly o r suddenly i n t h e magnitiide and d i r e c t i o n o f t h e v e l o c i t y along t h e s t r e a m l i n e . S t r i c t l y iiniforni flow r a r e l y e x i s t s i n such channels. The cross sect i o n of a t r a i n e d stream u s u a l l y has a simple geometric shape. The f l o w i n such a canal i s g e n e r a l l y considered t o be uniform, only having slaw changes of t i j r e c t i o n and no changes with d i s t a n c e i n t h e value of t h e v e l o c i t y along a s t r e a m l i n e , with t h e exception of s t r e t c h e s upstream of drops, weirs and d i v e r s i o n dams, where non-uniform flow occurs. The n a t u r a l r i v e r b e d , though o f t e n n o t s i i f f i c i e n t l y s t a b l e i n t h e short-term,

is a r e s u l t of the a c t i v i t i e s of e x t e r n a l n a t u r a l f o r c e s , and may be considered t o h e i n long-term e q i i i l i b r i i m with them. The p r i s m a t i c channel of a t r a i n e d r i v e r with a iiriiform flow cannot correspond t o t h e complicated conditions of the o r i p i n a l s t a t e and, d e s t r o v i n p t h i s long-term balance, freqiiently has a n e g a t i v e e f f e c t on some of the h a s i c natiiral functions of the stream o r r i v e r .

The b i o l o g i c a l eqiiilibrium i n t h e o r i g i n a l ecosystems on t h e banks is a result of an i n t e r p l a y of t h e o r i g i n a l groundwater l e v e l and corresponding s o i l moistlire f l u c t i i a t i o n . The conditions f o r t h e e q i i i l i b r i i m of a q u a t i c ecosystems depend on t h e i n t e r p l a y of water depth, flow r a t e s , the morphology and m a t e r i a l of t h e channel, and on t h e a q u a t i c f l o r a . E c o s y s t e m , both a q u a t i c and on t h e banks, g e n e r a l l y need heterogeneous c o n d i t i o n s f o r t h e i r development o r s u r v i v a l . These conditions a r e u n i f i e d by r i v e r t r a i n i n g , o r newly and uniformly e s t a b l i s h e d by t h e headrace o r t a i l r a c e c o n s t r u c t i o n .

l h i f i e d conditions a r e not acceptable

f o r many r e l e v a n t s p e c i e s . This r e s u l t s i n a d e c l i n e i n t h e i r h e t e r o g e n e i t y , s i g n a l i z i n g t h e d i s t u r b e d b i o l o g i c a l balance. These changes occur gradually from t h e beginning of t h e c o n s t r u c t i o n work. RiTJer t r a i n i n p , i f n o t accompanied hv t h e c o n s t r u c t i o n of weirs and dams t o

338 TABLE 4.21

Impact of r i v e r t r a i n i n g Hydraulic parame t e r s

Discharges

Water Table

Increased slope of t h e channel

Limited flooding

Extended cross s e c ti o n

Restructed Change i n water tempenatural fer- r a t u r e t i l i z a tion

Increased velocity of f l m

Restricted groundwater recharge

Increased drainage rate

Decrease i n Rise i n b a s e flow groundwater d u r i n g vepe- t a b l e tation period

Increase

Increase i n winter discha rres

Decrease

Change o f sedimentation and e r o s i o n

Increase i n infiltration

F l o r a and Fauna

helliqg value

Change i n water q u a l i t y

Increased flood control

Change i n water f l o r a

Improved a g r i c u l tiire

Decrease i n Change i n infiltrawater fauna including tion f i s h species

Deteriorated s o i l regenera t i o n

Drop i n gromdwater table

Improved navigation and hydropower genera t i o n

Waterlogging Excessive drainage

Chang? of riparian vegetation

improved a c c e s s i b i l i ty Negative impact o f water tourism

C h e c k l i s t of t h e probable impact of r i v e r t r a i n i n g on t h e w a t e r cycle and ripar i a n environnier.t. s w e l l t h e water t a b l e , results i n a s u b s t a n t i a l drainage e f f e c t . Such an e f f e c t m y be supported by t h e a s s o c i a t e d i r r i g a t i o n network and r e s u l t i n a 10-20% i n c r e a s e i n annual outflow i n the f i r s t 4-5 y e a r s a f t e r c o n s t r u c t i o n . I n the n e x t p e r i o d , t h e drainage impact on t h e annual outflow i s n o t as s u b s t a n t i a l and mainly occurs as a r e g u l a t i n g e f f e c t , i n c r e a s i n p low d i s c h a r g e s . Its e f f e c t on flood occurrence i s c o n t r o v e r s i a l . Decreased moisture content i n t h e upper s o i l l a y e r i n c r e a s e s t h e i n f i l t r a t i o n c a p a c i t y , thus lowering t h e s u r f a c e r u n o f f . The increased flow c a p a c i t y o f t h e r i v e r b e d , and e s p e c i a l l y o f t h e a s s o c i a t e d drainage network, i n c r e a s e s t h e flow v e l o c i t y and c o n t r i b u t e s t o t h e i n c r e a s e i n flood d i s c h a r g e s . The drainage e f f e c t of r i v e r t r a i n i n g and a s s o c i a t e d network i n c r e a s e s t h e p r o b a b i l i t y o f flood occurrence and t h e value of flood discharges, depending on t h e s o i l and moistlire c o n d i t i o n s , i . e . depending on t h e share of t h e balancing e f f e c t of t h e increased i n f i l t r a t i o n c a p a c i t y o f t h e drained s o i l layer.

339 River t r a i n i n g d r a s t i c a l l y changes t h e conditions f o r sediment t r a n s p o r t . This can also b e analyzed on t h e b a s i s of t h e following simple formula, derived from t h e water depth, the flow r a t e and t h e g r a i n s i z e o f t h e bed-load mixture

(4.33) de - c h a r a c t e r i s t i c g r a i n s i z e of t h e bed-load mixture h

- water depth

(m) fm)

v X - minimum flow r a t e causing the o n s e t of bed-load t r a n s p o r t (m. s-1 ) K

-

c o e f f i c i e n t o f t h e sediment t r a n s p o r t (almost s t a b l e and = 216 according t o Scharnow)

s-3)

River t r a i n i n g i n f l u e n c e s both t h e water depth and t h e flow r a t e s , and i n t h i s wav changes also t h e c h a r a c t e r i s t i c s i z e of t h e bed-load mixture and t h e i n t e n s i t y of t h e bed-load

t r a n s p o r t . T h i s change i n t h e bed-load t r a n s p o r t may

r e s u l t i n demands f o r f u r t h e r r i v e r t r a i n i n g i n t h e s t r e t c h downstream. River t r a i n i n g u s u a l l y has a p o s i t i v e i n f l u e n c e on t h e i c e regime i n t h e r e g u l a t e d s t r e t c h , b u t due t o i t s a c c e l e r a t i n g e f f e c t has n e g a t i v e impact on unregulated s t r e t c h e s downstream; Ttie n e g a t i v e impacts o f r i v e r r e p i l a t i o n r e s u l t mainly from t h e reduction of

the stream l e n g t h , frcm the extension o f t h e c r o s s s e c t i o n and from the renroval of t h e r i v e r s i d e v e g e t a t i v e campy. This augments t h e drainage e f f e c t , increases t h e flow r a t e s , a c c e l e r a t e s t h e outflow and, l i m i t i n g groundwater recharge, res u l t s i n the r e d u c t i o n of evaporation nad e v a p o t r a n s p i r a t i o n . River t r a i n i n g may r e s u l t i n c u r t a i l i n g t h e d u r a t i o n o f runoff from the source t o t h e e s t u a r y , even t o t h e e x t e n t of reducing i t t o h a l f the o r i g i n a l diiration. The decrease i n groundwater recharge l i m i t s t h e r e g u l a t i n g e f f e c t o f groundwater on s u r f a c e water d i s c h a r g e s , r e s u l t i n g i n a decrease i n average discharges d u r i n g t h e sumner p e r i o d and i n an i n c r e a s e i n discharges i n w i n t e r , thus causing

a drop i n a g r i c u l t u r a l production i n t h e a d j a c e n t a r e a . The impact o f

headrace, t a i l r a c e and f e e d e r , l i n k and o t h e r conveyance canals

i s more d r a s t i c : They change the groundwater regime and a s s o c i a t e d ecosystems, they may cause waterlogging with a s s o c i a t e d s a l i n i t y hazards i n v a s t a r e a s , they change t h e i n f r a s t r u c t u r e of t h e a r e 3

-

s e v e r i n g t h e cornminication network and

r e s t r i c t i n g t h e a c c e s s i b i l i t y of c e r t a i n a r e a s both f o r t h e population and the w i l d l i f e . T h e i r c o n s t n i c t i o n restricts w i l d l i f e occurrence, worsening t h e l i v i n g c o n d i t i o n s , e s p e c i a l l y o f r a r e s p e c i e s , and permits f i s h t o escape from r e s e r v o i r s and r i v e r s . Conveyance c a n a l s enable t h e t r a n s f e r of p o l l u t i o n and under c e r t a i n circumstances form favourable conditions f o r the occurrence o f i n s e c t s and f o r desease dissemination. Nevertheless, an improvement i n the conditions f o r water trans-

340 p o r t , power g e n e r a t i o n , o t h e r multi-purpose u t i l i z a t i o n o f w a t e r , s e t t l e m e n t , a g r i c u l t u r a l and i n d u s t r i a l production, r e c r e a t i o n form t h e precondition f o r a development boom i n the a d j a c e n t a r e a (Tab. 4.20). River t r a i n i n g has to be r e a l i z e d only as a n i n t e g r a l p a r t of an improvement i n t h e water regime i n t h e a d j a c e n t a r e a . I t i s , t h e r e f o r e , indispensable ( a ) t o simultaneously a c c e p t measiires f o r changinp t h e s u r f a c e runoff i n t o groundwater r u n o f f , e s p e c i a l l y on t h e f o r e s t and a g r i c u l t u r a l lands, (b)

t o simul taneously a c c e p t measures f o r achieving a b i o l o g i c a l equilibrium

i n t h e ecosystems of t h e r i v e r v a l l e y and t h e catchment, e s p e c i a l l y by d e t e m i n i n g t h e e c o l o g i c a l l y optimum r a t i o o f a r a b l e land, ( c ) t o s o l v e r i v e r t r a i n i n g problems n o t only h y d r a u l i c a l l y , t e c h n i c a l l y and economically, b u t a l s o from a n environmental p o i n t of view. Streams and r i v e r channels a r e formed by t h e lonffterm impact of hydrometeor o l o g i c a l , geological and b i o l o g i c a l processes. S u b s t a n t i a l changes i n the o r i g i n a l r i v e r bed, i n its r o u t e and i n t h e accompanying v e g e t a t i v e canopy during r i v e r t r a i n i n p m y d i s r u p t t h e balance which has been e s t a b l i s h e d by n a t u r a l f o r c e s and endanger t h e course of n a t u r a l f u n c t i o n s . Only when t h e c o n s t r u c t i o n r e s p e c t s t h e o r i g i n a l s t a t e , the main n a t u r a l functions

and b a s i c i n t e r r e l a t i o n s h i p s , a s occurs a f t e r minor amendments t o t h e

o r i g i n a l r i v e r bed and through t h e c o n s t r u c t i o n of p r o t e c t i o n dykes adapted t o the topography of t h e t e r r a i n , can t h e consequent state be p r e d i c t e d with s a t i s f a c t o r y accuracy and t h e r e f o r e be mnaged t o o f f e r maximum b e n e f i t s With minimized environmental l o s s e s .

341 Chapter 5

WATER DEVETBPMENT

5.1

ANI)

MANAGEMENT POLICY

WATER MANAGmW ACTIVITIES

ORGANIZATIONS

Water mnagement i s a complex of a c t i v i t i e s , designed t o meet t h e demands of economic development and aiming a t a n optimum development and u t i l i z a t i o n of water r e s o u r c e s , depending on t h e i r q u a l i t y and a v a i l a b i l i t y i n space and time, and a t t h e c r e a t i o n of an optimum l i v i n g environment, through t h e conservation of water r e s o u r c e s , t h e i r p r o t e c t i o n a g a i n s t exhaustion and d e t e r i o r a t i o n , and through t h e p r o t e c t i o n of human s o c i e t y a g a i n s t t h e harmful e f f e c t s of w a t e r . The r a t i o n a l management of water resources u t i l i z a t i o n has a s i t s aim, i n cormion with development g e n e r a l l y , an enhancement of t h e conditions f o r h w n l i f e and must, t h e r e f o r e , be recopnized as an i n t e g r a l p a r t of s o c i a l and economic development. I n periods of predominantly single-purpose water u t i l i z a t i o n , i n a r e a s with abundant w a t e r r e s o u r c e s , low population d e n s i t y , s c a t t e r e d snBll-scale i r r i g a t i o n networks and a l o w degree of i n d u s t r i a l i z a t i o n , s o c i a l and i n d i v i d u a l water requirements can be s a t i s f i e d by t h e a c t i v i t i e s of water u s e r s o r d i f f e r e n t l o c a l o r g a n i z a t i o n s . To achieve a h i g h e r production and a b e t t e r water u t i l i z a t i o n , various s p e c i a l i z e d o r g a n i z a t i o n s a r e formed w i t h t h e aim of ensuring water supply, and/or d i s p o s a l , i r r i g a t i o n development, power g e n e r a t i o n , inland n a v i g a t i o n , p r o t e c t i o n a g a i n s t floods e t c . I n t h e n e x t development s t a g e , r i v e r boards and o t h e r a u t h o r i t i e s a r e formed i n o r d e r t o achieve a g r e a t e r e f f i c i e n c y i n t h e management of w a t e r development t o c o o r d i n a t e t h e multipurpose water u t i l i z a t i o n and p r o t e c t t h e s o c i e t y a g a i n s t t h e harmful

( e f f e c t s of w a t e r .

The supreme r e g u l a t o r y a c t i o n concerning w a t e r , i n o r d e r t o meet t h e dernands

a r i s i n g o u t of h w n a c t i v i t i e s and t h e necessary p r o t e c t i o n of t h e environment,

is a government r i g h t and o b l i g a t i o n . The del-egation of a u t h o r i t y from t h e c e n t r e v a r i e s f r m country t o country and, i n t h e case of f e d e r a l i z e d and developing c o u n t r i e s , even w i t h i n t h e same c o u n t q , depending on t h e given soc i a l and p o l i t i c a l framework, t h e l e g a l regime of water management, t h e a v a i l a b i j i t y of w a t e r i n r e l a t i o n t o i t s u s e , and o t h e r r e g i o n a l d i v e r s i t i e s . Jxgal and i n s t i t u t i o n a l f a c t o r s p l a y an important r o l e i n t h e o r g a n i z a t i o n of t h e r e s p o n s i b i l i t i e s f o r water resources management. The i n s t i t u t i o n a l framework Is aimed a t s a t i s f y i n g t h e d i f f e r e n t i n t e r e s t s of all w a t e r u s e r s , and a l s o a t f a c i l i t a t i n g t h e c o r r e c t implementation of a l l water-related progranunes. Decision-<ing

p o l i c i e s and

i s i n v a r i a b l y c l o s e l y linked with t h e r e l e v a n t poli-

t i c a l , economic and s o c i a l processes which a r e t h e r e s u l t o f t h e i n t e r a c t i o n of

a niunber o f bodies (Tab. 5.1).

LAW cons ti t i i t ion c i v i l law p u b l i c works law labour l a w t a x a t i o n law

CIAKING

WATER ETANAGENENT water law enforcement r e g i s t r y of w a t e r r i g h t s c a d a s t e r of water r i g h t s r i g h t s of way f o r water uses

POTdlCY-PIAKING, n a t i o n a l water p o l i c v i n t e r n a t i o n a l waters policy water management strategy

& PLANNIVG n a t i o n a l o b j e c t i v e s and goals i n t e r n a t i o n a l poIicy s e c t o r a l development policy

water p r i c i n g legal tools reimbursement of c o s t s water a d m i n i s t r a t i o n

waterway development and maintenance hydrographical services water p o l l u t i o n control

inland navigation timber f l o t a t i o n r a i l way, highway and a i r t r a n s p o r t development

water supply f o r industry water p o l l u t i o n control

r i g h t s of way f o r water uses g r a n t i n g o f water r i g h t s water d i s p u t e s d e c i s i o n s

hydropower g e n e r a t i o n thermal and nuclear water f o r thermal & power development n u c l e a r power d i s t r i b u t i o n networks genera t i o n water p o l l u t i o n con t r o 1

water supply f o r irrigation l i v e s t o c k , processing and f i s h breeding water p o l l i l t i o n control

approval of w a t e r development p r o j e c t s p r o j e c t design project construction p r o j e c t operation technical a s s i s t a n c e

w a t e r law water uses law flood c o n t r o l law p o l l u t i o n control

law

IVTERIOR municipal developurban & r u r a l water ment SupPlY waste water t r e a t ment and d i s p o s a l water p o l l u t i o n control 1

w a t e r supply and use waste water d i s p o s a l

w

c N

~

AGRI( agricultural development i r r i g a t i o n drainage fisheries river training watershed management

1

E N V I R ONME NT P R 0 TE C T I 0 N n a t u r a l resources flood c o n t r o l erosion control

RECREATION

pol 111t i o n c o n t r o l

L

I

I

hydrologj c a l s e r v i c e s hydrogeological s e r v i c e s d a t a monitoring & processing h y d r a u l i c and hydrologic

research I n t e r r e l a t i o n s h i p between water management and o t h e r sectors.

I water supply f o r recreation waste water treatment and d i s p o s a l

recreation services n a t i o n a l parks administration tourism p r o m t i o n s p o r t promotion

I

343 Four basic groups can be distinguished among water management a c t i v i t i e s : (a)

legal administration,

(b)

development a c t i v i t i e s ,

(c)

economic a c t i v i t i e s (Tab. 5.2),

(d) o t h e r mnagement a c t i v i t i e s ( i n c l . services - Tab. 5.3). Depending on the individual c h a r a c t e r i s t i c s of a given country, the i n s t i t u t i o n a l framework f o r water resources management includes the agencies with polit i c a l and regulatory functions, working e . g. under regional a u t h o r i t i e s , and l e g i s l a t i v e bodies, working under a centralized water o r other national authori-

ty. I n order t o r e s t r i c t possible c o n f l i c t s and provide a view which unifies nationwide i n t e r e s t s , the supreme coordination is usually entrusted t o a spec i a l national authority, t o one of the ministries responsible f o r the various water development aspects such a s the Ministry of Water and Energy / Agriculture / Forestry / Public Works or t o a multi-sectoral commission o r special i n s t i t u t e . To avoid any ambiguity, the exercising r e s p o n s i b i l i t y has t o be separated from the administering arid controlling/monitoring responsibility. The d i v e r s i t y of i n s t i t u t i o n a l integration i n water management depends on the separate consideration of such s p e c i f i c problems as municipal and industrial water supply arid waste water disposal, groundwater development, i r r i g a t i o n and drainage, f o r e s t management, hydropower generation, inland navigation e t c . , and m y be r e f l e c t e d by the existence of various organizations fqr some of these purposes. Nevertheless, a l l matters r e l a t i n g to water should be regarded as forming p a r t of an i n t e g r a l whole based on the unity of the relevant catchments. The s t r u c t u r e of r i v e r boards corresponds t o t h i s t e r r i t o r i a l principle, whereas the i n s t i t u t i o n a l s t r u c t u r e of water supply and waste water disposal organizations o f t e n depends on the p a r t i c u l a r in-house p o l i t i c a l arrangements. I n order t o achieve the economic and s o c i a l goals of a country i n consideration of i t s environmental l i m i t a t i o n s , e x i s t i n g surface and groundwater resources have t o be assessed, t h e i r q u a l i t y , n a t u r a l functions and present uses for a l l purposes i d e n t i f i e d , the future demands i n the medium and l o n g t e r m estimated, and both the medium and long-term plans formulated on the basis of an optimization process. Water resources planning 3s an i n t e g r a l p a r t of water development and management i s a continuous process, whose implementation basically requires: (a) a fixed s t r a t e g y of water resources development and environmental protection, (b) a f l e x i b l e t a c t i c s of water requirements and withdrawals management, (c) an operational control and checking of water q u a l i t y and occurrence, water withdrawals, e f f l u e n t s and t h e i r q u a l i t y , in-stream water uses and of measures of environmental protection.

344 5.2

PAltZT,OXES

OF WAl'ER RESOTRCES DEVEILX'PEhT

The course of water requirements and water withdrawals is g e n e r a l l y d e t e r m i n i s t i c , whereas t h e course of water a v a i l a b i l i t y i s d e t e r m i n i s t i c only within the l i m i t s of t h e r e a l i s t i c f o r e c a s t o f groundwater and s u r f a c e water a v a i l a b i l i t y , which g r e a t l y depends on weather ( r a i n ) f o r e c a s t s . I t i s , t h e r e f o r e , b a s i c a l l y stochastic: i n t h e long teim. The occurrence of w a t e r requirements and s u r f a c e a v a i l a b i l i t y is u s u a l l y c o n t r a d i c t o r y : t h i s leads t o t h e f i r s t paradox which has t o be d e a l t with i n water resources development: IN THE PERiOD O F HIGH WATER REQUIREMENTS A S U B S T A N T i A L L Y LOWER WATER QUANT I T Y E X I . ~ T S I N I I A T U R A L UNREGULATED RESOURCES T.YAN .rtJ PERIODS

OF LOW WATER

PEOIJIRE,'IE:iTS.

A gradual i n c r e a s e i n t o t a l water requirnierlts freqiiently r e s u l t s i n

3

situa-

t i o n where, during water u t i l i z a t i o n , a p o i n t is reached when water requirements cannot be s a t i s f i e d by an i n c r e a s e i n water withdrawals from groundwater o r un-. r e g u l a t e d discharges only. The water a v a i l a b i l i t y has t o be r e g u l a t e d by a r t i f i c i a l water accunnilation. Daily and weekly f l u c t u a t i o n s can e a s i l y be balanced by small r e s e r v o i r s o r water tanks. Seasonal f l u c t u a t i o n s i n water requirements irlanifest a cornparatively high d i s p e r s i o n of minimuni and m x i m m v a l u e s , which c a l l f o r a n overu t i l i z a t i o n of a v a i l a b l e water resources and claim a s u b s t a n t i a l i n c r e a s e i n t h e parameters of r e l e v a n t development p r o j e c t s .

As the number of r e s e r v o i r s i n c r e a s e s , g r a d u a l l y less and less f e a s i b l e l o c a l i t i e s o r less f e a s i b l e arrangements f o r supplementing t h e required supply a v a i l a b i l i t y have t o be used, including d i s t a n t water r e s o u r c e s , deep groundwater s t r a t a , and, i n t h e l a s t s t a g e of development, even resources w i t h low q u a l i t y and unconventional water r e s o u r c e s . This is t h e reason f o r t h e rise i n t h e average investment, o p e r a t i o n a l and w i n t e n a n c e c o s t s f o r water resources withdrawal, conveyance, p u r i f i c a t i o n and d i s t r i b u t i o n . I n a d d i t i o n , e f f l u e n t s d e p r e c i a t e t h e q u a l i t y of a v a i l a b l e water resources and waste water treatment becomes necessary, thus f u r t h e r i n c r e a s i ~ n g r e l e v a n t c o s t s . This l e a d s t o t h e second paradox which has t o be d e a l t with i n water resources development: THE AVERAGE INVESTMEtJT AND OPERATIONAL CDSTS PER CUBIC METER OF WATER SUPPLIED GROWS E X P O l I E N T l A L L Y , EVEN

THOUGH THE S P E C I F I C COST OF WATER SUPPLY

FOR I N D I V I D U A L WATER DEVELOPMENT PROJECTS DECREASES DOWN TO A CERTAIN LEVEL WITH THE I N C R E A S I N G QUArJTITY OF WATER S U P P L I E D .

Problems a s s o c i a t e d w i t h a l a c k of water o r inadequate water q u a l i t y a r e solved by t h e c o n s t r u c t i o n and subsequerit o p e r a t i o n of water p r o j e c t s . Water development p r o j e c t s which have i n good time been implemented c r e a t e a temporaty surplus of w a t e r t h a t cannot be f u l l y u t i l i z e d inmediately a f t e r t h e i r com-

3 45 p l e t i o n . This leads t o t h e t h i r d paradox which has t o be d e a l t with i n water resources development : THE TEMPORARY SllRPLlJ.5 OF hA.TER OWER~TMG211 I!..TE?Z :Z< FOR WATER O V E R U T I L I Z A -

T I O l i WirTHOUT AIJY IMPORTAlr'T NEGATIVE E:CONOMIC ZFFECYZ, Fi..?l.!S

PRECO?:DITlONS FOR A

SUBSEQUENT WATER S C A R C I T Y .

Any p e r i o d of temporazy surplus of water ends by achieving an equilibrium between w a t e r resources and over-excessive water requirements. Any f u r t h e r lack of water i s again solved by c o n s t r u c t i n g a new p r o j e c t ( F i g . 5.1). This c y c l e

is t o be r e p e a t e d , extending t h e water resources development t o more d i s t a n t areas, u n t i l a s t a g e of a u t i l i z a t i o n o f economically f e a s i b l e water resources

is achieved. This leads t o t h e f o u r t h paradox t h a t has t o be d e a l t with i n water resources development: A L L A V A I L A B L E WATER RESOURCES A R E USEL, BEFORE E F F I C I E N T WATER-SAVING

TECM-

NIQUES A R E A P P L I E D .

1

I

I

Active balance

Gradual increase in

of water resaurces

water utilization

and needs

(and project efficiency)

investment and

P a ssive ba I a nc e

construction process

of water resources and needs

F i g . 5.1. Schematic i n t e r p r e t a t i o n of t h e c y c l e of water resources development and water use r a t i o n a l i z a t i o n . A s o c i e t y should form pre-conditions for i t s sound development by adapting

i t s w a t e r requirements t o water a v a i l a b i l i t i e s . But t h i s r u l e f u n c t i o n s under extreme s i t u a t i o n s only: When water a v a i l a b i l i t i e s are sharply r e s t r i c t e d , water

is used for indispensable u s e s only. The increased a v a i l a b i l i t i e s cause water t o be used f o r less and less necessary uses. Under t h e s i t u a t i o n of a long-term water s u r p l u s , growing w a t e r withdrawals d i f f e r more and more from t h e i n d i s pensable water requirements. This f a c t , accompanied by an exponential i n c r e a s e i n s p e c i f i c investment and o p e r a t i o n a l c o s t s caused by u t i l i z i r g less and l e s s f e a s i b l e p r o j e c t sites f o r growing t o t a l water withdrawals, leads t o t h e f i f t h paradox that has t o b e d e a l t w i t h i n water resources development:

346 GRADUALLY I N C R E A S I N G DEVELOPMENT COSTS GRADUALLY SAFEGUARD L E S S AND L E S S IMPORTANT WATER REQUIREMENTS.

STRATEGY OF WATER RESOURCES DEVELOPMENT

5.3

By formulating t h e desired water res'ources development o b j e c t i v e s , i t is possible t o e s t a b l i s h a s t r a t e g y f o r t h e r a t i o n a l conservation and step-by-step development of those resources: i . e . t o e s t a b l i s h procedures f o r i n c r e a s i n g the a v a i l a b i l i t y and subsequent u t i l i z a t i o n and d i s p o s a l of water re5ources. A conunon o b j e c t i v e is f o r example t h e conservation of t h e n a t u r a l functions of water resources w i t h i n t h e framework of t h e n a t u r a l environment, e s p e c i a l l y of the q u a l i t y and optimum a l l o c a t i o n of these water resources among present and p o t e n t i a l water u s e r s , i . e . t h p i r optimum multi-purpose u t i l i z a t i o n w i t h i n the framework of the e x i s t i n g and expected s o c i a l and economic s t r u c t u r e (Fig.

5.2). Tang-term planning, a b a s i c t o o l f o r helping t o achieve t h r s e o b j e c t i v e s , c o n s i s t s of the f o l l m i n g s t e p s : ( a ) i d e n t i f i c a t i o n of a v a i l a b l e s u r f a c e and groundwater resoiirces, evaluat i o n of t h e i r q u a l i t y and uses i n relevant categories of water u t i l i z a t i o n , which r e q u i r e s an information system o r i t s establishment; (b) evaluation of water denmnds i n t h e medium texm ( f i v e y e a r s ) and of water needs i n t h e long term, t o match t h e physical and socio-economic condit i o n s , n a t i o n a l and regional development plans ; t r e a t i n g i n t e r r e g i o n a l and i n t e r n a t i o n a l problems i n the context of n a t i o n a l i n t e r e s t s ; ( c ) compilation of balances of water resources and needs, d e t e c t i n g c r i t i c a l a r e a s , p r e s e n t and f u t u r e problems; (d) formulation of a l t e r n a t i v e scenarios and s t r a t e g i e s , appropriate f o r solving p a r t i c u l a r n a t i o n a l , regional and l o c a l problems; ( e ) optiniization and evaluation of these scenarios and s t r a t e g i e s , with respect t o t h e i r advantages and disadvantages, environmental and socio-economic after-effects,

o t h e r implications and unavoidable repercussions, b e n e f i t s and

l o s s e s , and, l a s t but not l e a s t , t h e investment, operation and associated costs required f o r t h e f u l l completion and successful operation of t h e p r o j e c t o r cornplex implenientation of required arrangements i n t h e framework of the present and f u t u r e socio-economic s t r u c t u r e ; (f)

s e l e c t i o n of t h e optimum scenario and s t r a t e g y , i . e . t h e most appro-

p r i a t e f o r s o l v i n g p a r t i c u l a r regional and l o c a l problems, capable of being pursued on a phased and f l e x i b l e b a s i s , taking i n t o account environmental and socio-economic l i m i t a t i o n s i n c l . t h e lack of s k i l l e d human resources and t h e i n e r t i a of l o c a l c u s t o m , obsolete s o c i a l s t r u c t u r e , t r a d i t i o n a l labour methods, jeopardizing e s p e c i a l l y t h e successful i n t r o d u c t i o n of modern a g r i c u l t u r a l p r a c t i c e s , and t h e implementation and operation of modem i r r i g a t i o n systems;

347

DE V ELOPM ENT SC ENA R I0S

!

Fig. 5.2. Block diagram f o r a l l o c a t i o n of water resources i n l i n e with development of t h e s o i l resources and i n d u s t r y . Any r a t i o n a l development tends t o the u l t i m a t e s t a g e of a sustained u t i l i z a t i o n of t h e n a t u r a l p o t e n t i a l by using the mininim [ratter and e n e r w , which should be checked i n relevant time horizons. (g) approval and acceptance of the p r e f e r r e d scenarios and s t r a t e g y by a l l c e n t r a l and regional a u t h o r i t i e s , involving t h e existence of an appropriate l e g a l and i n s t i t u t i o n a l framework and two-way co-ordination among a l l l e v e l s of responsible a u t h o r i t i e s during t h e planning process; (h) budgeting t h e gradual implementation w i t h i n t h e framework of medium-term p l a n s , whose aim i s t o i n t e g r a t e planned programes of d i f f e r e n t s e c t o r s , define i n f i n a n c i a l terms t h e annual n a t i o n a l , regional and l o c a l o b j e c t i v e s , and t o a l l o c a t e funds f o r achieving those medium-term objectives ; (i)

monitoring the p e r f o m n c e of t h e plan, modifying i t , i f required by

348 changed circunls tances, needs and p r i o r i t i e s . Significant goals i n mediiun-term plan implementation include the hannonization o f : ( a ) the development of the natural environment, balancing the needs of the u t i l i z a t i o n of natural resources and the necessity of environmental protection i n order t o decrease t h e negative impact of water u t i l i z a t i o n on the hydrolog i c a l cycle, which reduces the volume of water available and leads t o a deterioration i n its quality, (b) the water needs of present and potential water users with a view t o the required water q u a l i t y and quantity and to the optimum economic conditions.

To achieve the above goals, the following three principles have t o be respected: F i r s t principle of water development strategy: KEEPING THE DEVELOPMENT OF WATER RESOURCES I N L I N E WlTH THE OVERALL S O C I O ECONOMIC DEVELOPMENT

BY RESPECTING THE D I V E R S I T Y OF THE OCCURRENCE OF WATER

RESOURCES UNDER NATURAL C O N D I T I O N S .

direct pr 0 duct ion costs

3

Fig. 5.3. Graphic representation of the r e l a t i o n of the t o t a l d i r e c t production cost and the expenditure on inf r a s t r u c t u r a l investment and opera t i o n according t o Czuka (1975). Excess i n f r a s t r u c t u r a l capacity (path A A2 B B2 C) enables lower production costs. Economic development requires a proportional development i n the f i e l d s of both productive and i n f r a s t r u c t u r a l projects. Expenditures i n the sphere of the i n f r a s t r u c t u r e decrease the cost of d i r e c t production a c t i v i t y . Production costs

349 increase with decreasing i n f r a s t r u c t u r a l costs u n t i l a minimum infrastructtiral value is attained which is indispensable f o r obtaining any output from the d i r e c t production a c t i v i t y .

The national objective i s to increase production a t the minimum t o t a l c o s t , i . e . including the expenditures both i n d i r e c t production a c t i v i t y and i n the i n f r a s t r u c t u r e . The curve expressing t h e r e l a t i o n between d i r e c t production c o s t s , investment and operation costs i n the sphere of i n f r a s t r u c t u r e , a l s o including investment and operation costs f o r water development projects, is hyperbolic. It moves gradually away from the zero point i n time, due t o more developed and f i n a n c i a l l y more and more demnding investments. The way to technically more developed production may be twofold: ( a ) with d e f i c i e n t i n f r a s t r u c t u r a l capacity, requiring higher d i r e c t production c o s t s , (b) with excess i n f r a s t r u c t u r a l capacity, permitting d i r e c t production costs t o be maintained a t a low level. The development scenario with excess i n f r a s t r u c t u r a l capacity (A A2 R B2 C)

-

(Fig. 5.3) enables lower production c o s t s , thus forming more favourable product i o n s , a t t r a c t i n g productive investments and dynamically increasing living standards. The development scenario with d e f i c i e n t i ? f r a s t r u c t u r a l capacity, which appears i n countries with slowly developing economies (path A B1 B C1 C ) , leads to higher production c o s t s , which a r e then d i f f i c u l t to reduce i n the period of a s u f f i c i e n t i n f r a s t r u c t u r e . I t is therefore advantageous t o develop water investments belonging p a r t l y , i n some economic models, t o the production sphere, f i v e t o ten years before the f u l l development of the production sphere. Second principle of water development strategy: RESPECTING THE L I M I T S OF THE NATTIRAL ENVIRONMENT I N THE STAGE OF I T S FULL, RATIONAL A N D LASTING U T I L I Z A T I O N FOR THE SAKE O F HUMAN SOCIETY.

The basic objective of water development a s an integral p a r t of s o c i a l and economic development can be defined simply e i t h e r a s

-

the maximization of the l i v i n g standard f o r the population o r i n i t s second

extreme, under completely d i f f e r e n t local o r environmental conditions,

-

the safeguarding of the survival of the population. The second objective may appear a s decisive, not only under the s p e f i c i c con-

d i t i o n s of underdeveloped populated countries o r areas with extreme c l i m t o l o g i c a l conditions, but a l s o i n the conditions of some developed areas whose development has already exceeded the environmental l i m i t s , i . e . the potential of renewable n a t u r a l resources. As mentioned before feedbacks e x i s t , causing a d e t e r i o r a t i o n i n the environmental q u a l i t y a s a r e s u l t of any o v e r - u t i l i z a t i o n . The resources p o t e n t i a l of a c e r t a i n area can be defined as its a b i l i t y to s a t i s f y permanently t h e needs of society, a r i s i n g from its socio-economic deve-

3 50 lopment. I n can be expressed by a m u l t i t u d e of p h y s i c a l , chemical, b i o l o g i c a l and a e s t h e t i c values and be simply represented by t h e number of i n h a b i t a n t s whose nourishment and economic development i t i s p o s s i b l e t o p e i m n e n t l y s u s t a i n by a g r i c u l t u r a l o r o t h e r production. Overproduction i n excess of t h i s resources p o t e n t i a l i s t h e r e f o r e p o s s i b l e , but r e l e v a n t feedback causes a temporal o r perm n e n t d e t e r i o r a t i o n i n t h e environmental q u a l i t y . Water p o t e n t i a l , which forms an i n t e g r a l p a r t of t h i s resources p o t e n t i a l , can be defined by t h e - annual discharge of t h e s u r f a c e water and by t h e t a b l e and q u a n t i t y of t h e groundwater , - annual r a i n f a l l and t h e discharge c o e f f i c i e n t s ,

- minimmi discharges arid t h e flow d u r a t i o n curve - water q u a l i t y r e l e v a n t t o q u a n t i t y records o r t o t h e depth below t h e s u r f a c e . O v e r - u t i l i z a t i o n of t h e water p o t e n t i a l causes f i r s t t h e d e c l i n e i n t h e water q u a l i t y , and t h e second d e c l i n e of t h e environment. During t h e development of water resources l o c a l resources a v a i l a b l e nearby a r e used f i r s t . The u t i l i z a t i o n of t h e s e l o c a l water resources i s , i n t h e next development s t a g e , o f t e n replaced by mass water supply from s u b s t a n t i a l resources of g e n e r a l l y lower q u a l i t y . The i n t e r c o n n e c t i o n of these mass water supply networks g r a d u a l l y c r e a t e s r e g i o n a l w a t e r supply s y s t e m . The p o s s i b i l i t i e s of f u r t h e r e x t e n s i v e development a r e exhausted by long-distance water conveyance and by t h e c r e a t i o n of a n i n t e r r e g i o n a l system. Respecting t h e l i m i t s of the n a t u r a l environment means a r a t i o n a l approach frcm t h e s t a g e of a non-systenlatic u t i l i z a t i o n of water resources, depending on t h e i r a v a i l a b i l i t y and economic f e a s i b i l i t y , t o t h e u l t i m a t e development s t a g e of t h e f u l l , r a t i o n a l and l a s t i n g u t i l i z a t i o n of water resources without any important long-term impact on t h e n a t u r a l e q u i l i b r i u n . Third p r i n c i p l e of water development s t r a t e g y : MAXIMIZATION OF THE REQUIRED OK P O S I T I V E EFFECTS f3F THE PROJECT AND MINIM I Z I N G I T S S I Z E A N D NEGATIVE IMPACT.

This p r i n c i p l e is derived n o t only from t h e need of economic f e a s i b i l i t y , but a l s o from t h e previous p r i n c i p l e of r e s p e c t i n g t h e environmental l i m i t s . Ey d e c r e a s i n g t h e s i z e o f t h e p r o j e c t , i t s n e g a t i v e impact may a l s o be reduced and

reserves l e f t f o r t h e d i v e r s e f u t u r e needs of t h e s o c i e t y .

351 nutriment

inte r r u Dted

fertilizers-

compensatory link

Fig. 5.4. An indisperisabie precondition f o r t h e e f f i c i e n c y of any water development measures i s t h e maintenance of the uninterrupted s t r u c t u r e s of t h e system: i n t e r r u p t e d s t r u c t u r e s have t o be replaced by new ones, e.g. f e r t i l i z ing e f f e c t of floods a f t e r completed flood control measures has t o be compensated by a r t i f i c i a l f e r t i l i z e r s , which i s energy- and labour-intensive.

5.4

TACTICS OF WATER WNAGEMENT Water requirements and water withdrawals usually exceed, or tend t o exceed,

the r a t i o n a l water requirements. I n a d d i t i o n t o t h i s , e f f l u e n t s and excessive

water consumption impair water q u a l i t y , r e s t r i c t i n g i t s f u r t h e r u t i l i z a t i o n . The need t o search f o r means of managing a water economy usually a r i s e s a s a r e s u l t of an a c t u a l o r expected d e t e r i o r a t i o n i n water resources caused by the p o l l u t i o n of t h e area i n question or of a whole country. An adequate u t i l i z a t i o n of water resources and a proper c o n t r o l of the use of water a r e impossible without an adequate u t i l i z a t i o n of a l l a v a i l a b l e means, which a r e b a s i c a l l y : 1

(a) (b)

legal i n s t i t u t i o n a l (and o r g a n i z a t i o n a l )

i

(c)

technical

t

(d)

economic

e

( e ) personal and moral P The l e g a l , i n s t i t u t i o n a l , o r g a n i z a t i o n a l , t e c h n i c a l , economic and personal arrangements and c r i t e r i a which a r e required t o provide e f f e c t i v e t o o l s f o r the r a t i o n a l and i n t e g r a t e d development, use and conservation of water resources a t

352 the n a t i o n a l l e v e l a r e riot veiy d i f f e r e n t from those required a t t h e l o c a l l e v e l . Water withdrawals W, water consumption C and water p o l l u t i o n N a r e a function of the indisperisable water requirements Ri and of t h e above v a r i a b l e s :

From a s o c i a l p o i n t of view, i t is indispensable t o safeguard f i r s t of a l l t h e r e l e v a n t personal water requirements of any individuum a s a b a s i c precondition of h i s l i v i n g standard. This b a s i c q u a n t i t y i s t o be offered t o the individuum i n t h e optimum q u a l i t y and a t a r a t e which does not s u b s t a n t i a l l y restrict h i s l i v i n g standard. Water requirements and uses i n i n d u s t r y , a g r i c u l t u r e , e n e r g e t i c s and t r a n s p o r t a r e t o be safeguarded under d i f f e r e n t economic conditions, because these bodies d i r e c t l y b e n e f i t from water u t i l i z a t i o n . On the o t h e r hand, it is indispensable t o use a l l t h e above tools f o r t h e

p r o t e c t i o n of human s o c i e t y before tinuseful wastage, misuse and depreciation of water resources and before overexcessive water withdrawals, demands and arrangements t h r e a t e n o r have a negative impact on t h e environment, thereby restricting the f u t u r e development o r negatively influencing t h e l i v i n g standard o r l i f e - s t y l e of t h e s o c i e t y concerned.

A dominant economic c h a r a c t e r i s t i c of water u t i l i t i e s is t h e l a r g e investment i n fixed c a p i t a l , characterized by the capital-turnover r a t i o , i . e . gross annual revenues divided by t o t a l investment, ranging from 0.15 - 0.25 comparing with 0 . 3 t o 0.5 f o r o t h e r u t i l i t i e s and 2 . 0 f o r manufacturing i n d u s t r i e s . A negative r e l a t i o n s h i p e x i s t s between water p r i c e and t h e wzter quantity demanded. An increase i n p r i c e is a s s o c i a t e d with a reduction i n t h e q u a n t i t y demanded. P r i c i n g p o l i c y , by a f f e c t i n g water requiremerits, i s t h e e f f e c t i v e t o o l which can, i n r e l a t i o n t o o t h e r t o o l s , s a t i s f y t h e varied goals of water mnagemen t . Domestic, i n d u s t r i a l , a g r i c u l t u r a l and i n f r a s t r u c t u r a l water requirements a r e responsive t o p r i c e changes. Concerning domestic water requirements, the change frcm f l a t r a t e s t o metered r a t e s may r e s u l t i n a permanent decrease of sane 30 t o 40% i n water use. A decrease exceeding 60% was recorded a s a res u l t of warm water supply metering and paying s e p a r a t e l y f o r each f l a t , being a r e s u l t of a l t e r i n g b a s i c uses, e.g. using stoppers, dishpans etc. instead of constant flaw, r e p a i r i n g leaks i n t h e domestic p l m b i n g system etc. When t h e r a t i o of water management c o s t s t o t h e t o t a l s o c i a l property is r e l a t i v e l y small, water development and management expenses can be f u l l y covered e i t h e r from p r i v a t e o r from comon funds. There is a g r e a t d i v e r s i t y i n the degree of i n s t i t u t i o n a l i n t e g r a t i o n i n water mnagement, but t h e growing c o s t s of water development and management r e s u l t i n increasing s t a t e and internationa l coordination and f i n a n c i a l i n t e r v e n t i o n , and i n a general tendency t o ensure

3 53 t h a t t h e u s e r s who d i r e c t l y b e n e f i t frcm such c o n t r o l cover t h e cost. TABLE 5.2 Product

[.hit

m3

Definition Water-withdrawn from a stream. (delivered t o the user)

1.

Surface (raw, irr i g a t ion ) water

2.

Groundwater

3.

Drinking water

m3 m3

4.

Process water

m3

5.

Waste water

m3

6.

Treated waste water

7.

Sliidge

t

U t i l i s a b l e waste from waste water treatment and p u r i f i c a t i o n p l a n t s i n c l . recovered m a t e r i a l .

8.

Hydropower

liwh

Energy (average coiitiniious , peak, breakdown) generated by c o n c e n t r a t i o n of head and by s t o r a g e , i f r e q u i r e d .

m3

Symbol

Water withdrawn from a n a q u i f e r .

\dater corresponding t o d r i n k i n g water q u a l i t y standards, delivered t o the water u s e r .

Treated water d e l i v e r e d t o t h e watei u s e r f o r i n d u s t r i a l use. Waste water taken away by t h e sewerage system t o t h e stream o r waste water t r c a tment p l a n t .

Waste water t r e a t e d i n t h e waste water treatment p l a n t .

C l a s s i f i c a t i o n of w a t e r management products This tendency r e s u l t s i n t h e formation of river boards and water supply/ disposa 1 a u t h o r i t i e s a s econcmic o r g a n i z a t i o n s safeguarding t h e r e q u i r e d prod u c t s , productive and unproductive s e r v i c e s (Tab. 5 . 2 , 5.3). Hence, t h e t a s k of economic management t o o l s i s as follows: (a)

they p a r t i a l l y o r f u l l y f i n a n c e t h e main a c t i v i t i e s of water mnagement

o r g a n i z a t i o n s , which r e g u l a t e water development a c t i v i t i e s , (b)

they r e g u l a t e water withdrawals, water consumption and t h e q u a n t i t y and

quality of e f f l u e n t , ( c ) they r e g i l a t e i n d u s t r i a l and a g r i c u l t u r a l development, municipal and r u r a l development, water power g e n e r a t i o n , i n l a n d n a v i g a t i o n , water r e c r e a t i o n , thus also i n f l u e n c i n g t h e l i v i n g standard of the population, which is a l s o d i r e c t l y a f f e c t e d by t h e i r impact on t h e dom(-.stic water requirements. The determination of charges f o r water withdrawals, water consumption, in-

stream water u s e , water p o l l u t i o n , e f f l u e n t d i s p o s a l , as w e l l as v a r i a t i o n s and exemptions i n t h e s e charges and r a t e s , and using water f o r any of t h e mentioned purposes without charges, i n f l u e n c e s t h e s o c i a l e f f i c i e n c y of water u t i l i z a t i o n . Rut the degree of such i n f l u e n c e depends on l o c a l , and e s p e c i a l l y economic con-

354 d i t i o n s . These charges and r a t e s influence t h e water requirements of t h e populat i o n i n connection with the l i v i n g standard and s t y l e , i . e . t h e n e t income, standard of dwelling and s o c i a l customs. The influence of water r a t e s on a g r i c u l t u r a l water requirements rrainly depends on the cost-benefit r a t i o , on expenses f o r o t h e r arrangements needed f o r an increase i n a g r i c u l t u r a l y i e l d , on t h e market and c r e d i t p o s s i b i l i t i e s , and

on the I n e r t i a of t r a d i t i o n a l i r r i g a t i o n and o t h e r a g r i c u l t u r a l p r a c t i c e s .

TABLE 5.3 Water management services

Unit

Definition

symb0 I

Productive s e r v i c e :

2

1. Flood c o n t r o l

km

2.

s o i l protection

km2

3.

Maviga t ion

tkm

4 . Aquatic l i f e management

m3 .s -1

3 s-l

5.

P o l l u t i o n control m

6.

Other productive services

.

rn3 .s-l

Water resources rnanagement aimed a t p r o t e c t i o n a g a i n s t floods and erosion. Drainage and s o i l p r o t e c t i o n . Improvemerit of wateiways , operation of locks and flow c o n t r o l . Water d e l i v e r y and water resources mnagemeri t t o increase e specia 1l y f i s h production. Management of water resources t o restrict water p o l l u t i o n . Management of water resources t o enable production i n o t h e r product i o n s e c t o r s , e.g. water d e l i v e r y f o r pump storage p l a n t s etc.

N1

N2 N3

N4 N5

N6

Unproductive services : ~~

7.

Recreation and water s p o r t s

8.

Hydrmeteorolog i c a l services

9.

Other unproduc-

capita Per season

Management of water courses t o enable o r improve recration.

N7

Collection and processing of hydrometeorological data.

N8

Categorization of water management services. The impact of w a t e r rates on i n d u s t r i a l water demands depends on t h e r a t i o of the water supply and e f f l u e n t d i s p o s a l c o s t t o the t o t a l c o s t of production, on t h e i r influence on t h e development of t h e r e l e v a n t i n d u s t r i a l p l a n t , on the water-saving technology a v a i l a b l e , on t h e i n e r t i a of t r a d i t i o n a l production p r a c t i c e s , and, l a s t but not l e a s t , on t h e i r influence on t h e n e t income of t h e r e l e v a n t milagers ,

355 P r a c t i c a l water p r i c i n g systems generally represent combinations of the following watei p r i c i n g p o s s i b i l i t i e s : (a) (b)

Free of charge, i . e . p r i c e of water included i n general t a x e s ,

(c)

\dater r a t e s

S p e c i f i c water t a x ,

- per u n i t of water -

per u n i t of product

($ per 1 . s - l ) ($ per 1000 pc, per kldh)

- per u n i t of s e r v i c e s (tb) - lump sum, without r e l a t i o n t o t h e q u a n t i t y of water supplied. Rates can take the following f o r m ( a ) uniform r a t e s , dependent on t h e quantity supplied i n t h e r e l e v a n t categ o r i e s of water u s e r s , (b)

r a t e s with increase f o r increased q u a n t i t i e s (supporting water s a v i r g )

(c)

r a t e s with reductions f o r increased q u a n t i t i e s (supporting t h e develop-

ment i n the r e l e v a n t category of water u s e r s ) (d) seasonal (depending on t h e balances of water resources and requirements and supporting water saving i n t h e period of i t s d e f i c i e n c y ) . !dater r a t e per u n i t can be (a)

uniform

f o r a l l water u s e r s ,

( b ) d i f f e r e n t i a t e d (dependent on t h e s t a t e social and development policy: b a s i c q u a n t i t y f r e e clf charge, lower p r i c e s f o r p r e f e r r e d water u s e r s , e.g. f o r a g r i c u l t u r e , higher f o r high-income producers etc. ) (c)

dependent on water q u a l i t y (surface water, groundwater, t r e a t e d water

e t c . , c l a s s Ia, I b , 11, 111, I V ) , (d) dependent on t h e q u a l i t y of t h e product ( i n energetics f o r kbJh b a s i c , peak, breakdown e t c . ) ( e ) dependent on water consumption ( i n industry and e n e r g e t i c s ) . I n t h e case of water r a t e s per u n i t of water consumption, these can be (a)

uniforni,

(b)

categorised on t h e b a s i s of t h e consumption r a t i o ,

( c ) with a n i n c r e a s e f o r increased water consumption and a decrease f o r decreased consumption), ( d ) seasonal (increased during unfavourable balance of water resources and needs ) . Rates per u n i t of e f f l u e n t can be

(a) uniform, (b) w i t h l i n e a r or exponential progressive increase f o r increased p o l l u t i o n , ( c ) categorized according t o the category of p o l l u t e r ( a g r i c u l t u r e , industry, m u n i c i p a l i t y ) , (d) categorized on t h e b a s i s of t h e water q u a n t i t y and q u a l i t y i n the recip i e n t , c l a s s I a , l b , T I , 111, I V ,

356 ( e ) categorized on t h e b a s i s of t h e e f f l u e n t q u a n t i t y and q u a l i t y . J-egal t o o l s can achieve similar s t i m u l a t i n g fiirictions t o those of economic t o o l s namely through:

(a) o f f i c i a l d u t i e s ( f o r u t i l i z a t i o n permissions, discharge p e r m i t s , r u l ings e t c . ) p1 ( b ) s a n c t i o n rates, assessments p2 ( c ) f i n m ( e . g . f o r u t i l i z a t i o n of water i n v i o l a t i o n of v a l i d r e g u l a t i o n s ) (d)

recompenses e t c .

p3 '4

Expenses connected w i t h water development and management include (a)

management and c o n t r o l c o s t s

01 ( b ) o p e r a t i o n a l c o s t s f o r water withdrawal, d i s t r i b u t i o n , p u r i f i c a t i o n , waste water d i s p o s a l e t c . 02 ( c ) maintenance and reproduction c o s t s of water development p r o j e c t s (depreciation costs e t c . ) (d)

investment c o s t s

O3

O4

The balance of r e l e v a n t b e n e f i t s and expenses can be expressed by a simple equation

S

- s u r p l u s r e q u i r e d ( i f riecessary)

k - g r a n t s from o t h e r s e c t o r s and bodies

G

0

k

- expenses

ilk - accumulated charges f o r products connected with t h e water u s e

Nk

-

accuniulated charges f o r s e r v i c e s connected w i t h t h e water use

Pk - d u t i e s , f i n e s , recomperises e t c . ( i f incorporated i n economic t o o l s ) . The economic b a s i s f o r water resources development and management has t o be e s t a b l i s h e d by i n c l u d i n g o r excluding t h e above mentioned components i n t h e equation. Hence, t h i s i n c l u s i o n o r e x c l u s i o n and t h e l e v e l of t h e r e l e v a n t charges n o t only decide on t h e c r e a t i o n of f i n a n c i a l r e s e r v e s , on a timely a c q u i s i t i o n of t h e necessary means f o r o p e r a t i o n , maintenance, investment, adm i n i s t r a t i v e and o t h e r c o s t s , but a l s o on t h e u t i l i z a t i o n of water resources i n

a s o c i a l l y d e s i r a b l e manner, on t h e c o o r d i n a t i o n of t h e development r a t e , and, l a s t b u t n o t least, on t h e development of l i v i n g s t a n d a r d s . Bearing t h i s i n mirid, water rates should be determined on t h e b a s i s of t h e f o l lowi.ng f a c t o r s : (a)

reimbursement of expetises f o r :

357

-

operation,

-

administration,

-

investment f o r f u r t h e r development,

reproduction and modernization,

TAEU 5.4 Basic a i m i n

Factor water supply

waste water disposal

Reimbursement o r p a r t i a l reimbursement of emenses f o r : 1. F i n a n c i a l balance

a ) management and c o n t r o l

a ) maiiqyment and control

b ) operation and maintenance of water supply networks and f a c i l i t i e s

b) operation and maintenance of sewerage systems

c ) t h e i r modernization

c ) t h e i r modernization d) new waste water disposal proiects

d) new water supply p r o j e c t s

2. Factors of time

a ) seasonal l i m i t a t i o n s of availability b ) seasonal and d a i l y limitat i o n of requirements c ) long term l i m i t a t i o n of water needs due t o limited resources

3. Factors of c o n s u q t i o ? and concentration

4 . Factors of quality

5. Policy

a ) r e s t r i c t i o n of environmental p o l l u t i o n b ) seasonal and d a i l y cont r o l of waste water d i s posal c ) l i m i t a t i o n of l a s t i n g p o l l u t i o n due to r e s o u r ces p o t e n t i a l

a ) l i m i t a t i o n of concentrat i o n of t o x i c and o t h e r substances i n waste waters b) l i m i t a t i o n of water consum- b ) r e s t r i c t i o n of change i n p t i o n i n t h e long term ecosys term a ) l i m i t a t i o n of a c t u a l water consumption

decrease i n w a t e r r e q u i r e ments i n t h e production sphere

a ) decrease i n water pollut ion b) m a t e r i a l recovery

E f f e c t of water and waste water d i s p o s a l p r i c i n g on general ecoiponiic development and on the l i v i n g s tandard of population, e s p e c i a l l y on l w i n c c m e groups. E f f e c t of p b n a l t i e s and s u b s i d i e s on water use from e n v i r o p i e n t a l l y , r e g i o n a l l y and s o c i a l l y d e s i r a b l e viewpoint.

Categorization of t h e b a s i c f a c t o r s of water and waste water disposal p r i c i n g policy. (b) (c)

p a s s i v i t y of t h e balance of water resources and needs, l i m i t a t i o n of water consumption,

358 r e s t r i c t i o n of water resources pollution,

(d) (e)

overall development goals

The influence of economic tools on water withdrawals Id, water consumption C and water pollution N (BOD .nid3) 5 i n t h i s way W

C

5

N

9

can be expressed by a simplified equation 5.1

(m3.s-l, BOD5.

fl-3(%)-

=

(5.6)

An increase i n water r a t e s r e s u l t s i n a decrease i n water withdrawals, i n a decrease i n e f f l u e n t quantity and i n a decrease i n water consmption.

An exponential increase i n r a t e s f o r water pollution r e s u l t s i n a d r a s t i c

decrease i n water pollution

The a t t r i b u t e s of efficiency a r e associated with competitive prices. Theref o r e , the r a t e s should be varied with the required changes i n denland, consumpt i o n , water pollution and cost conditions. Water consmption can be influenced, i . e . decreased, by the introduction of special r a t e s or by associating water r a t e s with the value of the water consumption r a t i o 'MC>

'?Ic>

0

c1 < c2 < c3

(5.9)

Applying the forces of supply and demand, water withdrawals W can be expressed, according t o Hanlce and Davis (1971), a s a reversed and exponential funct i o n of p r i c e (5.10)

M

-

e K

- price e l a s t i c i c y or water withdrawals - constant, expressing t h e combined e f f e c t of other tools

unit r a t e

K = f ( l , i , t , e , p ) , and can be simply derived f r m indispensable water require-

ments Ri

K

=

k; 1

. Ri

(see paragraph 3.2)

(5.11)

359 I f price is t o be changed from 'M t o 2FI, the expected water withdrawal W2 can be estimated by taking the log transform

LO^ w1

=

Log K - e l ~ M 'g

Log W2

=

Lcg K

-

e log 2M

(5.12)

as well as by subtracting and rearranging t o find the water withdrawal W2 from the known values of the other variables: ~ o w2 g

=

e

.

(log 'M - log 2M) + log

w1

I n the water resources u t i l i z a t i o n secr-or of the econony prices a r e generally not determined by objective factors of supply and demand, but s e t by the pricing policies of u t i l i t y mnagers. They r a i n constant from the season of peak a v a i l a b i l i t y t o t h e season of peak demand. Available resources a r e used ine f f i c i e n t l y and inequities a r e imposed on the u t i l i t y ' s consumers. The season of peak water demands frequently occurs i n the period of low water a v a i l a b i l i t y . Water withdrawals i n the season of peak water dernand o r i n the period of low water a v a i l a b i l i t y a r e economically d i f f e r e n t fran those i n other periods: This water is high-cost water, because additional capacity must be provided i f requirements exceed the original capacity. By not varying water r a t e s t o r e f l e c t these cost differences, investments a r e larger than econanically j u s t i f i e d . The e l a s t i c i t y of water requirements and t h e i r s e n s i t i v i t y t o changes i n water r a t e s w r y according t o the d i f f e r e n t categories of water users. But i n any case the seasonal regulation of water r a t e s decreases the difference between the maximurn and ninimurn values of t o t a l withdrawais

(5.14) provided t h a t

Nf

and W correspond t o seasonal and constant prices respectively

which reimburse the same t o t a l amount. The application of seasonal water r a t e s f o r a hypothetical u t i l i t y can be i l l u s t r a t e d by two curves: mmin - curve representing off-peak water requirements (fcr the period of an e f f e c t i v e balance of u a t e r resources arid needs)

mmay. - curve representing peak water requirements ( f o r the period of a passive balance of water resources and needs) (Fig. 5.5). The constent average cost pricing l i n e is horizontal and implies that capac i t y stands a t some constant r a t i o t o peak water requirements. The average variable costs a r e assumed t o be constant and equal t o marginal costs. The in-

360

M water rates

3-

-3

m

S

M eonst

5

rn

P

I

Fig. 5.5. The e f f e c t of an increase i n water prices i n the season of increased water requirements and drop i n water a v a i l a b i l i t y and its off-seasonal decrease, safeguarding the same p r o f i t but increased efficiency i n water use according t o Hanke and Davis (1971). cremental costs of expansion a r e depicted by a proxy, average variable costs plus recorded capacity costs distributed over s i x months. Constant average prices r e s u l t i n inefficiencies during the period of peak The use of water requirements, demanding the needlessly excessive capacity W P' water i n the period of excess a v a i l a b i l i t y i s needlessly limited, leading t o withdrawals Wm. Seasonal prices produce higher off-peak requirements l d i and lower water re+ quiranents W during the period of lack of water. Water use i n the off-peak P season should be allowed u n t i l the relevant incremental costs a r e equated t o incremental value. By allowing t h i s expansion i n off-peak use there would be an efficiency gain, represented by the t r i a n g l e 123 (Fig. 5.5). I n the case of m x i m withdrawals during constant prices W the loss generated by the needP' lessly excessive capacity pricing r u l e is postulated f o r future years, s i g n i f i cant reductions i n water requirements can be expected, resulting i n investment savings. To relieve the problem of peak requirements occurring i n the period of low water a v a i l a b i l i t y and safeguard a dynamic water development (a) the water r a t e s should r e f e r t o the actual cost structure and actual cost of resources used o r saved by consumer decisions, (b) the water r a t e s should r e f l e c t operating costs with no, o r only a part i a l contribution t o capacity costs, i f the capacity of the available resources i s not adequately u t i l i z e d ( i . e . i n the period of a highly a c t i v e balance of water resources and needs), (c) the period of an equilibrium of water resources and needs, o r i f requirements exceed capacity a t the relevant price, the price should r e f l e c t both

361 operation and capacity c o s t s and should be adjusted upward t o r e s t r a i n water withdrawals t o t h e capacity l e v e l , and seasonal r a t e s should be determined t o r e s t r i c t t h e f l u c t u a t i o n of water withdrawals during peak and off-peak periods of demand. A s i m i l a r policy should be accepted to decrease water p o l l u t i o n by industry. NON-CONVENTIONAL TECFNIQIJES OF WATER IJSAGE

5.5

The programne i n keeping with t h e f i n a l phase of water development, when a l l s u r f a c e and groundwater resources a r e f u l l v u t i l i z e d i n the conventional way, includes

-

the general extension of w a t e r s a v i n g technologies, including non-convention-

a 1 water u t i l i z a t i o n and - using non-conventional water resources o r non-conventional techniques of water supply, i . e . (a) water, (b)

long-distance water conveyance and long-distance t r a n s p o r t a t i o n of conjunctive u t i l i z a t i o n of surface and groundwater resources,

( c ) groundwater mining and a r t i f i c i a l recharge, ( d ) watershed management aimed a t modifying t h e q u a n t i t y and timing of water production, ( e ) changes of t o t a l r u n o f f , namely changes of evaporation o r evapotranspir a t i o n r a t e , changes of snow and i c e melting,

(f) (g)

weather modification, d e s a l i n a t i o n , renovation of waste water, treatment of o t h e r l o r q u a l i t y

water .

5.5.1

Long-Distance

Water Conveyance and Long-Distance Transportation of Water

The problem of the long-distance conveyance and t r a n s p o r t a t i o n of water is b a s i c a l l y economic. During t h e conventional water supply t h e c o s t s f o r water withdrawals and treatment p r e v a i l :

Mw

+

Mt

<<

.L 3

fil

-

Mt

- specific

PIc

-

W

Mc

3

s p e c i f i c c o s t f o r withdrawal of 1 m of water

3

c o s t f o r treatment of 1 rn

($ p e r m )

3

of water

($ p e r m )

3 of water ($.m-4 )

s p e c i f i c conveyance c o s t f o r t r a n s p o r t of 1 m

The t o t a l s p e c i f i c c o s t Mo i s , t h e r e f o r e ,

Mo = M w + M t + Mc . L

($ per m3)

(5.16)

362 and

L

-

Mo

=

(rtc

r

=

Mw Mc

tc

.

1)

+

Vc

.

I,

(5.17)

Mt L

+

.

conveyance d i s t a n c e (lenEth of t h e headrace o r p i p e l i n e ) (m)

rtc- r a t i o of water supply and t r a n s p o r t c o s t s Water l o s s e s during water conveyance depend f i r s t on the constriiction of t h e conveyance s t r u c t u r e s and second on t h e i r length. Leaving the l o s s e s which occur during w a t e r withdrawal and treatment a s i d e , t h e water q u a n t i t y supplied can be simply expressed on t h e b a s i s of t h e q u a n t i t y withdrawn a s

D

=

(l-cw.L).W

-

D - water d e l i v e r y

W

3 -1 (m .s )

q u a n t i t y of water supplied

3 s-l (m . ) -1 - c o e f f i c i e n t of s p e c i f i c water conveyance l o s s e s (m )

- water c

(5.18)

withdrawal

The t o t a l expenses of water supply can be s i m i l a r l y derived as

D

.

(1

-

.

Mo = W

(1 -

(Mw + Mt) + D

cw

. T,) .

Mo

Cw

.

(Mo

L)

.

=

", +

.

Mc

.

Mt + (1

- Mc . L)

= Mw

J2

- cw . L) . Mc .

L

+ Mt

This equation can be s i m p l i f i e d t o ($ p e r m3)

(5.19)

Comparing tvo w a t e r conveyance p r o j e c t s of t h e same c a p a c i t y (Mcl

Mc2 , cwl cw2), a l i m i t h e d i s t a n c e e x i s t s which h a s t h e same t o t a l conveyance c o s t i n both c a s e s :

(1

-

w1

. Mcl

L,

Cw1

Lm)

=

id2

. W1

=

(1

*

Mcl

- cw2 . Jdm) . W2

( s e e eq. 5.18)

. Mc2

Mcl - Mc2 -

=

cw2

Lm

.

G1

(m) *

(5.20)

Mc2

- marginal transport distance, .1.e. one alternative is m r e

r e q u i r i n g t h e same c o s t s i n both a l t e r n a t i v e s , f e a s i b l e f o r longer conveyance d i s t a n c e s and t h e o t h e r (with hi.Rher conveyance l o s s e s ) f o r s h o r t e r ones.

3 63 The above equation i s v a l i d only f o r comparing p r o j e c t s which have t h e same c o s t s f o r water withdrawal and treatment. I t goes without saying t h a t t h i s l i m i t i n g t r a n s p o r t d i s t a n c e depends on t h e discharges d i v e r t e d , t h e i r q u a l i t y and purpose of t h e i r u t i l i z a t i o n . The same equation can be applied f o r t h e option of t r a n s p o r t i n g water from surplus a r e a s t o water-short

a r e a s by using cistern wagons, tankers o r tawing

manmoth containers o r blocks of icebergs. The r e a l i s t i c d i s t a n c e from t h e source t o t h e r e c e i v e r has t o be i n t h e o r d e r of below 2500 h,and t h e maximum s i z e of t h e container approaches some 1.5 m i l l i o n m3

5.5.2

.

Conjunctive Use of Surface and Groundwater Resources

"he volume i n groundwater resources exceeds by more than a thousand times

t h e volume of f r e s h water i n a l l water courses. Half of t h i s amount is a v a i l a b l e a t a depth below 1000 m y but i t s q u a l i t y i s n o t s u f f i c i e n t l y known and t h e r a t e

of i t s n a t u r a l replenishment is extremely low ( s e e Tab. 1.1). The over-excessive e x t r a c t i o n of water from groundwater resources has t h e same c h a r a c t e r a s mining minerals and causes s i m i l a r environmental e f f e c t s : settlement of t h e E a r t h ' s s u r f a c e , ecological damages , diminution of discharges i n r i v e r s and streams, d i f f i c u l t i e s with both s u r f a c e and groundwater q u a l i t y etc. Pumping from deep a q u i f e r s is energy-demanding. Owing t o the high f l u c t u a t i o n of water t a b l e s , which is due t o changing l i f t s , pumps o f t e n work under condit i o n s of low pumping e f f i c i e n c y . The temperature of water from deep a q u i f e r s is o f t e n higher and depends not only on t h e depth b u t a l s o on the geological age of t h e s t r a t a , - younger geological formations contain water of higher temperature . Nevertheless, a q u i f e r s can be s u c c e s s f u l l y used i n conjuction with s u r f a c e water resources, e s p e c i a l l y i n t h e period of peak demands and i n dry periods. Thick, i n t e r s t i t i a l a q u i f e r s i n n a t u r a l dry c o n d i t i o n s , or only f i l l e d up with water t o a minor e x t e n t , can be used a s underground r e s e r v o i r s t o s t o r e l a r g e q u a n t i t i e s of water of acceptable q u a l i t y f o r t h e period of peak requirements. A r t i f i c i a l i n f i l t r a t i o n can i n c r e a s e t h e q u a n t i t y of water i n groundwater resources by t h e h e l p of i n f i l t r a t i o n b a s i n s , channels and a r t i f i c i a l channels, i n f i l t r a t i o n g a l l e r i e s and wells, working i n t h e period of excess water i n surface resources. An overpumping of these groundwater resources i n the period of drought may c o n t r i b u t e considerably t o balance water a v a i l a b i l i t y and needs even i n t h e period of peak demand ( s e e paragraph 5.5.3). The conjunctive use of s u r f a c e and groundwater resources means a coordinated u t i l i z a t i o n of a v a i l a b l e water discharges a s w e l l a s r e s e r v o i r s and compensation f o r a lack of water i n two o r more successive dry years by groundwater f o r seasonal, annual and carry-over s t o r a g e .

364 Withdrawal

of

contaminated groundwater

7 I I SPRINKLING

degasification , aeration ( s a t u r a t i o n by free 02)

I

J

RETENTION

Sedimentation

I N F I LTR AT ION

Biochemical processes A c t i v i t y of Fe and Mn bacteria Consumption of organic and anorganic carbon, changes in p H and redox potential ( + )

OXIDATION coagulation

Fez+ Fe3+ - e Mn2+ = M n 4 + + 2 e

Crystallizo t ion o f minerals

( + energy) ( + energy)

!

Inflow into groundwater aquifer

Fig. 5.6. Flow c h a r t diagram representing t h e b a s i c processes of the u t i l i z a t i o n of geological strata t o change water q u a l i t y , explored by Hatva and Reijonen (1972).

365 The drop of t h e groundwater t a b l e provokes a more e f f i c i e n t n a t u r a l recharge, a l s o from n o n - u t i l i z e d s t r a t a which do not normally c o n t r i b u t e t o t h e groundwater reserve of t h e a q u i f e r i n question. The volume of water e x t r a c t e d from

groundwater resources i n a dry year may, under favourable geomorphological and topographical c o n d i t i o n s , even exceed the average annual recharge, provided t h e s u r f a c e r e s e r v o i r s safeguard t h e recharge during wet years. The conjunctive use of s u r f a c e and groundwater resources a l s o forms condit i o n s f o r water s t o r a g e i n locations where c o n s t r u c t i o n of a s u r f a c e r e s e r v o i r is not f e a s i b l e , o f f e r i n g p o s s i b i l i t i e s f o r economizing on t h e s i z e of reserv o i r s and t h e i r use f o r carry-over s t o r a g e . I t r e s t r i c t s t h e space requirements f o r water development p r o j e c t s , thus enabling b e t t e r u t i l i z a t i o n of t h e land surface. I n t h i s way t h e a v a i l a b i l i t y f o r o p e r a t i o n a l runoff regulaLion is u t i l i z e d i n an i n t e g r a t e d and environmentally f e a s i b l e manner, r e s t r i c t i n g t h e ev,iporat i o n losses and a l s o improving t h e water q u a l i t y : a r t i f i c i a l recharge o f f e r s favourable conditions f o r water treatment (Fig. 5.6). Amox t h e o t h e r advantages of t h e conjunctive use of s u r f a c e and groundwater resources, the c m s t r u c t i o n i n s t a g e s should be mentioned: t h i s enables the step-by-step

connection of t h e new resources t o the e x i s t i n g system of mass

water siipply f o r population, i n d u s t r y and a g r i c u l t u r e . The conjunctive use of slirface and groundwater resources economizes on t h e c o n s t r u c t i o n of t h e d i s t r i bution and drainage network f o r i r r i g a t i o n : t h e groundwater t a b l e can be regul a t e d by means of r e l e v a n t recharge and supply w e l l s , arld t h e l i n i n g of d i s t r i bution canals can be r e s t r i c t e d , because the p e r c o l a t i o n l o s s e s recharge t h e groundwater r e s e r v e . A more f l e x i b l e i r r i g a t i o n regime f a c i l i t a t e s t h e i r o p e r a t i o n , making i t p o s s i b l e t o punp o u t s i d e t h e period of peak energv demand. The nuin o b s t a c l e s to a d e s i r a b l e development of the conjunctive use of s u r f a c e and groundwater resources include: (a)

gaps i n t h e i n v e s t i g a t i o n of deep a q u i f e r s ,

(b)

technical problems of w a t e r l o a i n g and clogging during i n f i l t r a t i o n ,

( c ) higher operational c o s t s due t o higher consumption of energy during e x t r a c t i o n of groundwater from deep a q u i f e r s , (d) i n s t i t u t i o n a l gaps and d i v e r s i t y i n i n v e s t i g a t i o n of surface water and groundwater (see paragraph 3.1) , ( e ) t h e lack of c o m n understanding between t h e r e l e v a n t s u r f a c e and groundwater s p e c i a l i s t s as w e l l a s t r a d i t i o n .

366

5.5.3

Groundwater Mining and A r t i f i c i a l Recharge

Under special economic and environmental conditions

groundwater can be

extracted as an exhaustible recource of fixed supply on a mining-yield basis. Mining yield is a t o t a l volume of non-renewable water i n an aquifer, analogous t o a mineral deposit (see paragraph 3 . 2 ) . Five types of overdraft have to be recognized according t o Snyder (1955) : (a) Developmnt overdraft, a necessary f i r s t stage i n groundwater developm n t i n t h a t withdrawals cause a lowering of the water table i n areas of natural recharge and discharge. This permits f u l l u t i l i z a t i o n of the i n t e r action between the components of the hydrologic cycle. (b,c) Se2SOMl (annual) o r cyclical (periodic) overdraft, both characterized by a zero n e t change i n water levels over a specified interval of time. Seasonal overdraft occurs when water levels a t the beginning of the pumping season remain the same from year t o year, but a r e i n a continual s t a t e of decline during pmpirg seasons. Cyclical overdraft e x i s t s when water levels decline over two o r m r e seasons, but eventually return t o t h e i r original level. These types of overdraft a r e r e l a t i v e l y unimportant and depend a great deal on the seasonal o r annual demand f o r water. (d) Longrun overdraft is perennial pumping i n excess of natural. replenishment, which m y lead, ultimately, t o depletion. (e) C r i t i c a l overdraft occurs when pumping leads t o some undesirable physical result, restoration from which i s technologically o r economically impossible.

I f environmental r e s t r i c t i o n s (see paragraph 5.5.2) a r e not taken into account then long-run overdraft i s profitable as long as annual n e t revenue from water mining exceeds the capitalized annual loss i n value of recharge. Assuming t h a t natural replenishment is constant and independent of the stage of storage development, Domenico and others (1968) determined the optiml-mining yield as - Mw "rq-Tp-

- Gr

r

(5.21)

($.m3>

Mw

-

n e t u n i t value of water a t the beginning of pumping

k$

-

marginal c o s t of pumping

r

-

r a t e of i n t e r e s t

Gr

-

natural recharge

(m3

S

=

7 dh - water

(m. m-3)

level decline per u n i t of storage withdrawal

GI.m-4>

367 A s a marginal c o s t of pumping becomes high, o r t h e i n t e r e s t rate becomes

small, t h e mineable v o l m e is low, which i n d i c a t e s t h a t a s u s t a i n e d y e i l d policy is d e s i r a b l e . Equilibrium s t o r a g e is achieved when the r a t e of e x t r a c t i o n is equal t o n a t u r a l ( o r n a t u r a l and a r t i f i c i a l ) replenishment. The optimal water use p o l i c y then s p e c i f i e s use r a t e s below n a t u r a l recharge when s t o r a g e i s below

i t s equil.irbium value, t h e tendency being t o move toward equilibrium s t o r a g e . A r t i f i c i a l recharge of groundwater m y be d-efined a s the planned a c t i v i t y of man t o augment t h e n a t u r a l i n f i l t r a t i o n of p r e c i p i t a t i o n , s u r f a c e and o t h e r water i n t o underground f o m t i o n s with the o b j e c t i v e t o (a)

reduce o v e r d r a f t and replenish depleted a q u i f e r , s t o r e water f o r periods of lack of s u r f a c e water o r f o r periods of sub-

(b) s t a n t i a l drop i n water q u a l i t y of o t h e r resources. (c)

t r a n s p o r t water t o t h e l o c a l i t y of use,

(d)

maintain t h e requested groundwater l e v e l (equilibrium s t o r a g e ) ,

(e)

prevent i n t r u s i o n of low q u a l i t y water,

( f ) improve t h e water q u a l i t y by i n f i l t r a t i o n , and, under special circumstances , fg) dispose urnanted w a t e r , i n d u s t r i a l and mining wastes a s well a s toxic substances . Methods of a r t i f i c i a l recharge may be c l a s s i f i e d according t o Huisman and Olsthoorn (1982) i n two groups: ( a ) i n d i r e c t methods (induced recharge) i n which increased replenishment i s obtained by l o c a t i n g t h e means f o r groundwater a b s t r a c t i o n a s c l o s e a s practica b l e t o a r e a s of n a t u r a l discharge o r e f f l u e n t s . ( b ) d i r e c t methods, i n which water from s u r f a c e sources is conveyed t o s u i t a b l e a q u i f e r s where it is made t o p e r c o l a t e i n t o a body of grounchater. Direct methods of a r t i f i c i a l recharge a r e t o be p r a c t i s e d mainly when: ( a ) s e a l i n g of a r i v e r bed s e r i o u s l y reduces t h e capacity of n a t u r a l i n f i l tration, (b)

t h e r i v e r bed is not i n d i r e c t c o n t a c t with t h e s u j t a b l e a q u i f e r ,

( c ) t h e supply area is f a r away from a s u i t a b l e l o c a t i o n of induced recharge, (d)

t h e surface water r e q u i r e s treatment o r s t o r a g e , which can be avoided

by a q u i f e r recharge. The choice of t h e a p p r o p r i a t e method of d i r e c t a r t i f i c i a l recharge is governed mainly by topographic, geologic and economic conditions : ( a ) when t h e a q u i f e r extends t o t h e ground s u r f a c e , shallow ponds formed by a network of dikes and l e v e e s , f u r t h e r d i t c h e s and furrows,adapted t o i r r e g u l a r t e r r a i n , m d i f i e d dry stream beds or r e l a t i v e l y f l a t land may be flooded t o i n c r e a s e t h e a r e a over which i n f i l t r a t i o n occurs aEd extend i t s duration,

365 (b) when t h e a q u i f e r is s i t u a t e d a t m d e r a t e depth, i t can be replenished through s h a f t s , p i t s and b a s i n s , e . g . through abandoned gravel p i t s , ( c ) when confined and unconfined a q u i f e r s a r e s i t u a t e d a t some depth below t h e ground s u r f a c e acd are topped by a semi-pervious o r i q e r v i c u s l a y e r , they can be replenished through we1 Is and g a l l e r i e s .

5.5.4 Watershed Managemea t Watershed management is the planned use of land t o conserve n a t u r a l resources and produce renewable one5 by an appropriate fonn of land and resources use 2nd mn-use, by m d i f i c a t i o n s t o the v e g e t a t i v e canopy and o t h e r measures t o change s u r f a c e runoff i n t o groundwater rvnof f . Vegetation e x t r a c t s water from the s o i l and t r a n s p i r e s it i n t o atmosphere, thus reducing t h e t o t a l r u n o f f . Land management p r a c t i c e s designed t o a f f e c t the volume and timing of the s u r f a c e and p-ounhrater runoff involve modifications t o t h e v e g e t a t i v e canopy. Timber h a r v e s t i n g methods which reduce evapotranspiration r a t e s and increase snowmelt include block and s t r i p c u t t i n g a s w e l l a s thinning. Heavy vegetation, phreatophytes, with a deep and extensive r o o t system, a l s o e x t r a c t s water from deeper s t r a t a which a r e normally a f f e c t e d by evapotranspiration. Clear-cut watersheds y i e l d a n increase of 20%, even recharging 450 mi i n humid a r e a s . A reduction i n phreatophytes r e s u l t s i n a 5

- 15% increase:

t h e rPplacement of old

f o r e s t s by young ones increases water y i e l d s , as does t h e conversion of pine f o r e s t s i n t o hardwood f o r e s t s t o o , due t o t h e g r e a t e r i n t e r c e p t i o n l o s s e s and t h e longer period o f i n t e n s i v e t r a n s p i r a t i o n of evergreens. The conversion of brush o r chaparral

i n t o g r a s s , and f o r e s t s i n t o forbs and

shrubs generally increases t h e flc#w from the watershed. But t h e water y i e l d m y drop below t h e o r i g i n a l v a l u e , when e . g . t h e grassland is lush from s u f f i c i e n t

water supply and e f f i c i e n t f e r t i l i z a t i o n . Water y i e l d s which a r e obtained by v e g e t a t i o n conversion and/or removal and f a l l back t o t h e o r i g i n a l , pre-treatment l e v e l s with regrowth o r a s the n a t u r a l cover becomes re-established.

The y i e l d increment corresponds t o the d i f f e r e n c e

i n water requirements o f f t h e o r i g i n a l and converted v e g e t a t i v e canopy. The change a f f e c t s t h e n a t u r a l ecosystems, with a possibly negative impact on wildl i f e and h a b i t a t . Management a c t i v i t i e s m y involve problems with erosion, peak

flows and water q u a l i t y . Water y i e l d increases a r e economically f e a s i b l e i f combined with o t h e r f o r e s t management o b j e c t i v e s , e s p e c i a l l y timber production. Runoff phenomena a r e t h e i n t e g r a t e d r e s u l t of o v e r a l l watershed behaviour. The l a c k of understanding of t h e causal mechanisms l i m i t s the degree t o which data obtained frcm p i l o t s t u d i e s can be extrapolated f o r complex watersheds i n o r d e r t o f o r e c a s t i n t e g r a t e d hydrological responses on watersheds under d i f f e r e n t geomrphological and climatological conditions.

3 69 The type of vegetation can to a certain degree a l s o a f f e c t the amount of water transpired. But evapotranspiration depends m r e on the climate: i t s r a t e

i s extremely high wherever heavy and dense vegetation, energy and rmisttre input occur together. The suppression of evaporation i s , therefore, of key importance i n tropical areas, especially i n a r i d and semi-arid areas. Measures t o decrease the evaporation include i n particular: (a) surface-area reduction (removal of phreatophytes, groundwater storage, reservoirs with minimum r a t i o of area t o storage, narrowing and straightening of channels e t c . ) (b) reduction i n moisture gradient (e.g. by limitation of a i r circulation by windbreaks) (c) reduction i n energy input (e.g. by protecting the surface by mechanical covers - roofs, floating r a f t s , screens o r granulated material reflecting solar energy) (d) evaporative suppressants (layers of porous material, dust mulch, quickly drying cultivated surface s o i l layer, pebble and paper m l c h , chemical a l t e r a t i o n of the s o i l surface e.g. by polyelectrolytes , thin impervious layers which form resistance i n the evaporation process). One of the basic tools available for the suppression of both evapotranspiration and evaporation a r e filrns of mnomlecular thickness, e.g. the longer carbochain alcohol mixtures, straight-chain f a t t y alkanols i n c l . hexadecanol , octadeconal, ethylene oxide, dosoconol, ethylated ethers e t c . A l l these chemicals have to be non-toxic, having no detrimental effects on m n , f i s h , fowl and wildlife. They must form a thin continueus impervious layer, penetrable by raindrops and closifig again a f t e r being broken, pervious t o oxygen and carbon dioxide. It i s generally cheaper t o use powdered monolayers for t h i s purpose than liquid f o r m such as hot solutions and emulsions. The effects of mnolayers on food chains i n open lakes have been found t o be negligible, with some beneficial interference with insect occurrence. The physical and chemical changes i n water quality, such as a s l i g h t increase i n water temperature and dissolved oxygen, have been found to be minor and not adverse. Any increase i n bacteriological populations can be easily controlled by addition of norm1 bactericides. The degi-ee of the reduction i n evaporation and evapotranspiration varies with the thickness of the applied film and with the kind of surface or plant. It also depends on the deterioration e f f e c t of winds, which occurs on free water surfaces a f t e r winds with a speed in excess of 8 km per hour. According t o Haeussner (1972) reduction r a t e s of 8 - 14% are reported for reservoir surfaces, and higher rates for smaller reservoirs. Reduction rates of up t o 40% and 20% are reported for bare s o i l s and c i t r u s trees :-espectively. Due t o the degrada-

370

tion, the m a x i m e f f e c t on reservoir surfaces within the first day decreases t o a value of some 15%of the i n i t i a l one within about ten days. The quantity and timing of water production from glaciers, ice and snow can be achieved by a change i n the albedo. A thin layer (1 m) of l i g h t ashes, coal dust, foundry sand e t c . can be used for t h i s purpose, r e s d t i n g i n a reduction i n the albedo from 0.6 to 0.1 and an increased r a t e of melting, depending on the s o l a r energy input. Under favourable conditions the yield from glaciers can be doubled. According t o Meir (1964)

the mentioned charge 3 2 i n the albedo r e s u l t s i n an increment of 2.4 m of water from 1 m of glacier

surface. The disadvantages of t h i s practice of runoff augmentation include the following negative environmental effects (a) temporary deterioration in the scenary, which is otherwise a t t r a c t i v e from the recreational point of view, (b) water pollution by fine suspended matter, which i s nevertheless not important from the water use point of view. Depending on the balance of the hydrologic cycle, water which has been a r t i f i c i a l l y withdrawn i n t h i s way can be recharged naturally. I f not, the following practices for decreasing the r a t e of t?e melting process and the a r t i f i c i a l recharge of water i n glaciers have proven feasible: (a) (b)

insulatory cover of the glacier surface, e.g. sawdust,

snow breaks, weathe.modification, i . e . cloud seeding i n winter. (c)

5.5.5

Weather Modification

Water from the atmosphere cap be extracted by various techniques of vapour condensation. -These practices concern both the lower and upper layers of the atmosphere. The moisture of the low atmosphere layers can be a r t i f i c i a l l y condensed, the m t u r a l interception and fog drip increased and an accumulation of the resulting flow achieved by various technical measures and cultivation practices, such as by tree or other wood plantations i n locations with favourable conditions for vapour condensation, by vegetative measures on and arrangement of the land surface, the i n s t a l l a t i o n of impervious sheets, the i n s t a l l a t i o n of constructions with p l a s t i c f i b r e s , acting as water condensers and collectors, by applying various chemicals and by e l e c t r i c a l means. The f e a s i b i l i t y of such measures and arrangements depends on local conditions. Satisfactory quantities of Water can be gained especially i n areas with a high a i r humidity, being frequently i n clouds , o r where ground fogs are frequent

time and: submuntain areas.

-

i n mountains , mri-

371 A r t i f i c i a l Frecipitation, augmenting natural r a i n f a l l within meteorological l i m i t s a t a given place and time, requires a comprehensive understanding of the physics of r a i n f a l l occurrence. The problem of weather m d i f i c a t i o n consists especially in: (a) determining the need of t h i s treatment and i t s j u s t i f i c a t i o n , (b)

recognizing a s u i t a b l e opportunity, method of delivering the required treatment, method of evaluating the r e s u l t of t h i s treatment, unpredictable impact on long-term changes of climate, compensating f o r economic benefits and losses i n the areas affected,

Cc) (d) (e) (f) and for possible adverse impacts on the environment. Rainfall and snowfall can be influenced by changes i n the heat balance i n the atmosphere. Its equilibrium can be affected e.g. by cool water pumped from deep ses layers. A feasible technology f o r gaining more w2ter from showers over agricultural areas i n surnner and increasing snowfall o r r a i n f a l l i n rrountains i s offered by clouc. seeding. This technology consists i n dispersing condensation nuclei s i l v e r diiodide AgJ2, a m n i u m n i t r a t e NH4N03, compounds of urea and t h e i r corn binations, other hygroscopic materials , e. g. finely divided comnon s a l t NaC1, by burning propane and acetone solutions of s i l v e r diiodide o r by the e l e c t r i c disintegration of the various compomds whose product t h i s s i l v e r diiodide is. Cloud seeding is practised from a i r c r a f t o r d i r e c t l y from the ground surface, using upward a i r currents. The a i r pass movement cannot be determined with the required accuracy, unless limited by a land surface, e.g. by a mountain barrier. But uncertainty s t i l l remains, i n the case of both cold and warm cloud seeding, because the r a i n f a l l mechanism is extremely complicated (Fig. 1.8) ; it depends on a i r conditions including wind p r o f i l e s , updraft velocity, on a p o d supply of supercooled liquid droplets and low concentrations of freezing nuclei, on the course of the coalescence growth process e t c . Sumner cumulus producing moderate showers and shallow winter clouds, formed by the muntain-produced l i f t i n g of mist a i r , o f f e r suitable seeding opportun i t i e s . The seeding of heavy s u m e r r a i n clouds and deep winter clouds can even decrease precipitation i n comparison with the normal r a t e . Current techniques have l i t t l e value i n areas with very lcw r a i n f a l l occurrence and during dry periods i n areas of medium precipitation. The best r e s u l t s are still achieved i n regions where, and during seasons when natural r a i n f a l l is mst likely. The evaluation of the r e s u l t s of cloud seeding is based on probabilistic methods. Due t o the great variations of precipitation Over time and space, methods which compare the target area and control area data a r e mre r e l i a b l e

372 but not s u f f i c i e n t l y f r e e of u n c e r t a i n t y . The economic e f f e c t s and l o s s e s caused by cloud seeding bring ahout s e r i o u s problems of compensation o r reimbursment. This treatment m y not only cause excessive floods o r h a i l events, but a l s o avalanches i n muntajnous a r e a s . I t negatively a f f e c t s o t h e r a r e a s as well, where a s u b s t a n t i a l decrease i n rainf a l l may occur. Cloud seeding which r e s u l t s i n increased p r e c i p i t a t i o n over continental a r e a s with a p r e c i p i t a t i o n deficiency and reduces p r e c i p i t a t i o n over s e a s i s the only case where t h i s discrepancy does n o t appear. The e f f i c i e n c y of cloud seedirrg, ranging frcm 8 - 15 percent of t h e expected values f o r annual r a i n f a l l ( t h e l i m i t of a p o s s i b l e increase by improved a p p l i c a t i o n being estimated a t sow 30%), may under favourable conditions be of c r u c i a l importance f o r saving the harvest i n c r i t i c a l dry periods.

5.5.6 Desalination and Treatment of Taw-Quzlity Waters Water d e s a l i n a t i o n and t h e treatment of low-quality waters may prove t o be prac’ i c a b l e s o l u t i o n s t o t h e problem of water shortage i n c e r t a i n r e s t r i c t e d a r e a s . S a l i n i t y c o n t r o l measures which reduce t h e s a l i n i t y of s u r f a c e water discharges include: ( a ) point source c o n t r o l , i n s u l a t i o n of a l o c a l i z e d a r e a or removal of a source which cuntribl!tes an extremely s a l t load t o t h e system ( i n s u l a t i o n of s a l t plugs, d i v e r s i o n o r d e s a l i n a t i o n of s a l t y s p r i n g s , mine drainage, decreasing the t a b l e of s a l t y groundwater, b e n e f i c i a l consumptive use of t h e s a l t y water w i t h i n t h e catchment, u t i l i z i n g s a l i n e r e t u r n flow from i r r i g a t i o n e t c . )

,

(b) d i f f u s e source c o n t r o l , i . e . control of s a l t concentration and disposal spread over l a r g e a r e a s ( c o l l e c t i o n and consumptive u s e , evaporation, d e s a l t ing, measures of watershed mnigement e t c . ), (c) reduction of evaporation and evapotranspiration ( e s p e c i a l l y i n regions of groundwater recharge , improving i r r i g a t i o n e f f i c i e n c i e s , by watershed

management measures i n c l . phreatophyte removal e t c . ) , (d)

d e s a l i n a t i o n of the discharge.

Most n a t u r a l waters a r e not s u f f i c i e n t l y s u i t a b l e f o r d e s a l i n a t i o n , but pre-

treatment can s u f f i c i e n t l y m d i f y t h e i r q u a l i t y f o r subsequent - d i s t i l l a t i o n processes,

-

membrane processes, i . e . e l e c t r o d i a l y s i s and reverse osmosis, chemical processes , e s p e c i a l l y by ion exchange, c r y s t a l i z a t i o n , e s p e c i a l l y freezing processes.

Tnese techniques can be applied for t h e d e s a l i n a t i o n o f sea water, s u r f a c e and groundwater a s w e l l a s f o r the d e s a l i n a t i o n of g e o t h e m l water resources. Desalting processes a r e s t i l l economically f e a s i b l e only under s p e c i a l c i r c u m stances, being used almost exclusively for drinking o r feed water supply. The basic problems involved i n d e s a l i n a t i o n a r e

373 (a) (b)

high energy input requirements, disposal of r e s i d u a l s a l t s .

Similar problems a r e a l s o encountered i n techniques f o r t r e a t i n g low q u a l i t y waters e . g . heavily polluted waste water f o r re-use, which a r e e s s e n t i a l l y concerned with t h e r e m v a l of nitrogenous compoundF, phosphorus, heavy metals, o t h e r dissolved inorganic compounds, a s w e l l a s with the i n a c t i v a t i o n of pathogens.

5.6

CONCLIJSIONS

A t p r e s e n t , a t t h e dawn of a combined popu1at:on

and technological boom, it

is indispensable not only t o d e c l a r e , but a l s o t o safeguard i n a r a t i o n a l and planned manner the r i g h t of mankind and of each individual t o l i v e i n s u f f i ciency and beauty. It i s , t h e r e f o r e , e s s e n t i a l t o accept population growth and t h e a s s o c i a t e d development of heterogeneous demands a s t h e b a s i c c r i t e r i o n f o r making decisions concerning t h e a l l o c a t i o n of water and o t h e r n a t u r a l resources. The u t i l i z a t i o n of water and o t h e r n a t u r a l resources is a precondition of economic g r m t h . The dramatic pace of c u r r e n t economic development, however, i s based on an o v e r - u t i l i z a t i o n of these resources. While some n a t u r a l resources (such a s a i r , water and s o i l ) a r e renewable, they may - and increasingly do become gradually d e t e r i o r a t e d a s a r e s u l t of the secondary e f f e c t s of t h e i r development. An o v e r - u t i l i z a t i o n and excessive d e t e r i o r a t i o n of n a t u r a l resources, results i n a d d i t i o n a l and i n o r d i n a t e r e s t r i c t i o n s on f u t u r e development. I t i s , t h e r e f o r e , absolutely necessary t o manage t h e given developmmt process w i t h i n t h e framework of the biosphere, taking i n t o account t h e nmerous

functional r e l a t i o n s h i p s a s w e l l a s environmental c o n s t r a i n t s , and t o make optimum use of a l l water and f i n i t e n a t u r a l resources. The recognition of t h i s nm r e s p o n s i b i l i t y f o r i n t e g r a t e d development/biosphere management is a c r u c i a l f i r s t s t e p t o achieving s u s t a i n a b l e economic growth. To rove towards t h i s p o l i c y , i t is p o s s i b l e to choose optimum scenarios by means of m d e l 1ing and optimization. The very s e r i o u s environmental c o n s t r a i n t s which could a r i s e through the i n t e r a c t i o n of a g r i c u l t u r a l , i n d u s t r i a l , urban and r u r a l development on the one hand and t h e biosphere on the o t h e r hand m y r e q u i r e such measures a s : - t h e r e v i s i o n of rawlwaste material use/re-use and waterlwaste water u t i l i z a tion i n industry,

-

t h e r e v i s i o n of land use p a t t e r n s and forestry/agricultural/irrigation

practices etc. A new and complex i n t e r d i s c i p l i n a r y theory has t o be developed f o r t h e approach described above, p e n e t r a t i n g i n t o every a c t i v i t y of mankind. The pres e n t monograph attempts t o f o m l a t e a t least p a r t of t h i s theory, t h e theory of water development and management, from t h i s p o i n t of view and s o form the

3 74 basis f o r a deeper understanding between c i v i l engineers, economists, natural s c i e n t i s t s and other s p e c i a l i s t s involved i n the gradual change i n current practices towards a r a t i o n a l and balanced u t i l i z a t i o n of t h e biospheric system

in this particular field.

375 RFFERENCES Achtnich, W . , 1957. D i e F e s t s t e l l u n g des Wasserbedarfes a l s Voraussetzung ekes Sinnvollen Einsatzes der Beregnung, P e r r o t B i b l i o t e k , 3 , Calw. Albrecht, F . , 1951. D i e Vethoden z u r Bestimmung der Verdunstung d e r naturlichen Erdoberflache. Archiv f u r Meteorologie, Geophysik und Bioklimatologie, S p r i n g e r v e r l a g Wien. Arthur Mc, A . G . , Cheney, W.P. 1965. The e f f e c t of management p r a c t i c e on streamflow and sedimentation from forested catchments. Jour. I n s t . Engs, A u s t r a l i a ; 417-425. Avakyan, A . B . , 1977. Problems of environmental p r o t e c t i o n i n building reser- . v o i r s . TIN Water Conference, Mar del P l a t a . Balek, J . , 1977. Hydrology and water resources i n t r o p i c a l Africa. E l s e v i e r Amsterdam, Oxford, N e w York, 207 pp. Belyaev, I . , Zimin, I . 1975. Computer a s s i s t e d procedures i n water p r o j e c t evaluation. IIASA Research Report, Vienna, 32 pp. Benetin, J . 1958. Pohyb vody v zemine, (Water flow i n s o i l ) SVTL, Bratislava Roughton, W.C. 1970. E f f e c t s of land management on q u a n t i t y and q u a l i t y of a v a i l a b l e water. University of New South Wales, Water Research Laboratory, Report No. 120, 330 pp. Bugliavello, G . , Gunther F, 1979. Computer systems and water resources. Development i n water science, 1 , Elsevier, Amsterdam, Oxford, New York. Biilavko, A . G . , 1971. Vodnyj balans retchnych wodosborow . (Water balance of r i v e r s ) Gidrometeoizdat , Leningrad. Bul;&k, J . , 1976. Normy moSst& a j a k o s t i odpadnkh vud. (Standards of waste water qua 1i t y and quanti ty) 10. konf erence vodohospodrifd v prCmyslu. CSVrS, Praha. BuliCek, J . , 1977. Voda v zemPdPlstvi, (Water i n a g r i c u l t u r e ) SZN Praha, 294 pp. Canter, L.W., 1983. Impace studies for dams and reservoirs. International Water Power & Dam Construction, No. 7, Sutton.

Chow, V . T . , e t a l . 1964. Handbook of applied hydrology, Mc Graw-Hi11 New York e t c . 1200 pp. C r i t c h f i e l d , H . J . , 1966. General climatology. P r e n t i c e Hall Inc. Englewood C l i f f s , N.Y. 420 pp. Czepa, O . , Schellenberger, G . , 1956. Uber den Waxmehaushalt des Rreiten Lucinund Haussees b e i Feldberg. Acta Hydrophysica, Rand 111, Berlin. Czuka, J . , 1975. P o s s i b i l i t i e s of r i v e r basin development depending on hvdrolog i c a l and economic backqround. lWP/IJN I n t e r r e g i o n a l Seminar on River Basin and I n t e r b a s i n Development, Budapest. G b e l k a , J . , 1963. Vn6trozemskC vodne' cesty (Inland Waterways), SmL B r a t i s l a v a , SNTL Praha. s 439-460. Cebotarev, A. 1., 1975. Obschtchaja hidrologia (General Hydrology) Gidrometeoizd a t , Leningrad, 544 pp. Dale, M.B., 1970. Systems analysi's and ecology. Ecology Vol. 51 No. 1. Duke IJniversity P r e s s . Delfs, J . , 1956. Konnen w i r d i e Wasserlieferung aus dem Wald durch f o r s t l i c h e Massnahmen beeinflussen? Die Forst und Holzwirtschaft 2211956. kmenico, P A . , 1972. Concepts and models i n groundwater hydrology. Mc Graw-Hill i n t e r n a t i o n a l series. New York e t c . Dub, O . , 1957. Hydrologia, hydrografia, hydrometria (Hydrology, hydrography, hydrometry). SVTL B r a t i s l a v a , SNTL Praha. 526 pp. Eidmann, F.E., 1956. Die I n t e r c e p t i o n i n Buchen und Fichtengestanden. P u b l i c a t i o n No. 48 de I'Association I n t e r n a t i o n a l e S c i e n t i f i q u e .

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Fahlbush, F . , 1983. Optimum capacity of a run-of-river power plant. International Water Power & Dam Construction, No. 3, Sutton.

Fishbein, L., 1976. Environmental m e t a l l i c carcinogens: an overview of exposure l e v e l s . Journal of Toxicology and Environmental Health 2/1976. C o k e ' , A.F., 1977. Handbook of dam engineering. Van Nostram Reinhold Company, New York, p. 17, 58, 59. Graf, W.H., 1983. The hydraulics of reservoir sedimentatlon. International Water Power & Dam Construction, No. 4, Sutton.

376 Hanke, S.H, Davis, R . K . , 1971. Demand management through responsive p r i c i n g . AWWA Journal No. 9/1971. pp. 555-560. Helvey, J.D., P a t r i c , J . H . 1965. Canopy and l i t t e r i n t e r c e p t i o n of r a i n f a l l by hardwoods of e a s t e r n TJnited S t a t e s . Water Resources. Res 1. pp. 193-206. Hargraeves, G . H . , 1965. Consumptive use derived from evaporation pan d a t a . Proceedings ASCE.IR1 pp. 9'-105. Hibbert, A . R . 1967. Forest treatment d f e c t s on water y i e l d , Forest Hydrcjlogy, W.E. Sopper & H.W. L u l l , Pergamon P r e s s . Holman, M.A., 1961. A n a t i o n a l time budget f o r t h e y e a r 2000, Sociologv and Social Research 1/1961,,New York. Hol?, M . , 1978. P r o t i e r o z n i ochrana ( P r o t e c t i o n Against Erosion) SNTL Praha, SVTL B r a t i s l a v a , 283 pp. Hal?, M., 1971. Water and t h e environment, I r r i g a t i o n and drainage paper. FA0 Rome. Hol?, M . , 1976. ZBvlahov6 stavby, ( I r r i g a t i o n Works), SNTI, Praha, Alfa B r a t i s l a v a , 445 pp. Huisman, L., Olsthoorn, T . N . , 2983. A r t i f i c i a l Ground Water Recharge, Pitman Boston, Tnndon, Melbourne, 320 pp. J e d i ? , M . , 1966. VodohospodSfskB funkce a problemy vodniho d i l a RozkoS. Water management functions and problems of t h e Rozkos P r o j e c t . Vodni hospodsfstv; No.4. Praha. 1970. Economic considerations i n the f i e l d of water resources. W P - P l a n Organization Teheran. 1972. Water p i i c i n g . UNDP-MdP Teheran. 1973. Water resources development policy of I r a n . UNDF-MP Teheran. 2973. I n t e g r a t e d water resources development i n water s c a r c e countries. 1. World Congress on Water Resources Chicago. 1973. Co-ordination of water resources development. UNDP Teheran. 1977. Vodn; hospodri2stv; (Nater management) CWT Czech Technical University, Praha . 1978. InvestiCni probl6my vodniho hospo&r'stvi (Investment problems of water Czech Technical University, Praha. resources development) &TJT 1979. Step-by-step comparison of water resoiirces u t i l i z a t i o n . UN Water Seminar Cas telgandol fo. 1980. New approach of teaching water management a t u n i v e r s i t i e s . UNESCO Seminar on Water Resources Education, S m l e n i c e . 1980. PotFeba a spotfeba vody (Water demand and water consumption Publikace MLVH - Ministry of Forest and Water Management, Praha. 1982. Vliv ElovPka na obPh vody (The Impact of man on t h e hydrological cycle. Energeticky i n s t i t u t , Praha. 1983. Vodni hospodrifstv;, (Water Management) SNTL - S t a t e Technical Publishing House, Praha. J e t e l , J . , 1971. S y s t h y k l a s i f i k a c e chemismu podzemnich vod na zAklad6 iontovjrch kombinaci, (Systems of groundwater c l a s s i f i c a t i o n ) . Hydrogeologicka' mrenka 1969-70, pp. 127-134. Praha-Pmo. Kellogg, W.W., 1977. E f f e c t s of H m n A c t i v i t i e s on Global Climate, IdMO Publication No. 486, Geneva. Korziin, V . I . , Sokolov, A . A . , 1977. World water balance and world water resoiirces. 1% Water Conference, Mar del P l a t a . Kovacs , . G . , 1981. Seepage hydraulics. Developments i n water science, 10, Elsemer Amsterdam, Oxford, New York. Kraatz, D . R . , 1971. I r r i g a t i o n canal l i n i n g . I r r i g a t i o n and drainage paper. FA0 Rome. KreZmer, V . , Pe?ina, V . , 1971. Hospodakkr! zpdsoby a vodohospoda'fsk8 funkce l e s a . Lesnicka pra'ce, (Forest management and water management function of f o r e s t s . ) No.6. Kutilek, M . , 1966. Vodohospo&fska pedologie, (Water management pedology). SNTL Praha, SVTL B r a t i s l a v a . 275 pp. Lamb, H . H . , 1972. Climate, p r e s e n t , p a s t and f u t u r e . Metheun, London. Lambor, J . , 1955. L i e f e r t der Wald Wasser? Wald and Wasser, Hilchenbach. Zagler e t a l . , 1969. Man-made l a k e s . FA0 Rome, 71 0.

-

-

377 J m t h e r , S . , 1963. Das Abwasser i m Landwirtschaftlichen G r o s s b e t r i e b . Menge und Reschaffenheit VEB Verlaq h i p z i g . Likens, G . E . , e t a l . 1977. Rivkeochemistry of a f o r e s t e d ecosystem Springer. Verlae New Y o r k , Heidelberg, B e r l i n . 146 p. Maas, A., e t a l . 1962. D e s i w of water resources systems. Harvard University P r e s s , Cambridge, Mass. Mc Mahon, T.A., Hein, R.G., Reservoir c a p a c i t y and v i e l d . Developments i n water s c i e n c e , 9. E l s e v i e r Amsterdam, Oxford, New York. 212 pp. Mason, J . , 1957. The physics of clouds. Monographs on meteorology. Oxford. Manila1 f o r t h e compilation of water resources and needs. 1974. l h i t e d Nations, ECE,AJATF:R/5, New York. 80 p . Minasian, R . G . , e t a l . 1977. Water supply f o r steam and nuclear p l a n t s and p r o t e c t i o n of water bodies. UN Water Conference, Mar d e l P l a t a . Nejedl?, A . , 1976. K o t s z c e Easov6 prostorove' s t n i k t u r y j a k o s t i vody v toc;ch. ( P r o b l e m of water q u a l i t y changes i n r i v e r s . ) VPdeckotechnicka' konference k 1O.vyroEi Povodi Ohl'e, Chomutov. NesmPrAk, I . , 1972. Deterministicka' a stochasticka' s l o i k a v Casov6 Fad6 hodnot u k a z a t e l e j a k o s t i vody v t o c i c h ; ( D e t e r m i n i s t i c and s t o c h a s t i c c o T o n e n t s of water qu?l i t y i n r i v e r s . ) Sbomik konference CSVrS Ochrana Zivotniho prosti-edi, Praha. Nizery, A . , R o u s s e l i e r , M . , 1951. Aspect economique de l a sedimentation des r e s e r v o i r s . 3. Cnngress ICOLD New Delhi. Penman, H . L . , 1948. Natural evaporation from open w a t e r , b a r e s o i l and g r a s s . Froceedings Royal S o c i e t y of London, A 193. P h i l i p , J . R . , 1969. Theory of i n f i l t r a t i o n . Advances i n hydro-science, 5. p. 216-296. P i l s b u r y , A.F., Degan, A . , 1968. S p r i n k l e r i r r i g a t i o n . FA0 Rome. P i t t e r , P . , 1975. Technologie vody. (Water technologv). SNTL Praha. P l a i n e r , J . , 1977. Vodohospod2fskS b i l a n c e . (Water b a l a n c e ) . SZN Praha. 186 P . P o t t e r , G . L . , E l l s a e s s e r , H.h7., Mac Cracken, M . C . , L u t t e r , F.M., 1975. P o s s i b l e c l i m t i c impact o f t r o p i c a l d e f o r e s t a t i o n . Nature, 258. p. 697-698. Ramly E l , N . A . , Congdon, C . F . , 1975. D e s a l t i n g p l a n t inventory. Report No. 5 . O f f i c e of Water Research and Inventory, Washington. k i h a , J . , 1?78. Teoreticke zSklady p r o hodnoceni $razovych vlastnost: vody v prostPed1. ( T h e o r e t i c a l a s p e c t s of water a e s t h e t i c s ) . f i v o t n P p r o s t r e d i e 4 . p . 213-217. Stragkrabovg, V . , 1976. Uliv udolnich nadri; na obsah o r g a n i c w c h l S t e k v Iece. {Impact o f r e s e r v o i r s on t h e content of orEanic m a t t e r . ) Nove' pozMtkV 111-16. VUVH B r a t i s l a v a . Sumwara. M . . e t a l . . 1975. Tank model. UNESCO/lJMO Svmosium and workshops on &-liea p p l i c a t i o n of mathematical m d e l s i n hydrology' and water resources sys terns. B r a t i s l a v a . Sembera, J . , 1979. Syste'my Iizen; vodniho hospodsfstv; (Systems o f water management c o n t r o l ) . SZN. Praha. Todd, D . K . , 1967. Groundwater hydrology. John Wiley & Sons, Inc. New York. Thornwaite, C.W., 1948. An approach towards a r a t i o n a l c l a s s i f i c a t i o n of climate. Geogr. Rev. 38. p . 55-94. Uhlmann, D . , 1975. Hydrobiologie. VEB Gustav F i s c h e r Verlag Jena. p. 11-65. Votruba, L., HroSa, V . , 1980. Hospodaten; s vodou v nddrgich. (\dater Management i n r e s e r v o i r s ) . SNTL Praha, Alfa B r a t i s l a v a . 443 pp. LJolmn, M.G., Schick, A.P., 1967. E f f e c t s of c o n s t r u c t i o n on f l u v i a l sediment, urban and suburban a r e a s of Maryland. Water Resources Research. IJundt, IJ., 1953. Gewasserkunde. Springer Verlag B e r l i n , Gottingen, Heidelberg. I

,

378 AIJTHOR INDEX

Albrecht, 11

Czepa, 12

Hatva, 364

Achtnich, 195

Czuka, 348

Henry, 96

Alekin, 68

Hewlett, 279 Davies, 201 Holeman, 52

Appleyard, 146 Davis, 159, 358, 360

Holmn, 132

Arthur, Mc, 283 Darcy, 28

Holi, 190

Avakyar?, 309 Delfs, 274

Honert van den, 15 Balcerski, 231

Denit, 198

Bayer, 315

Domenico, 366

Bele, 280

Dooge, 289

Renetin, 177

Dub, 13

Hugh-Blair Smith , 240 Hubbert, 31 Huismn, 367 Hus’ek, 82

Blumenstock, 44 ECE, 228, 238 ISO, 124

Borland, 309 Eidman, 274

Iwasaki, 66

Bosch, 279 Boughton, 282

Fahlbusch, 113

Braslavskij, 12

FAO, 188

Brune, 311

FINA, 116

Kalinin, 282

Budyko, 275

Fishbein, 294

Karpov, 282

Bulavko , 285

Florea, 66

Kellogg, 269

Bulifek, 173

F o j t , 282

Koelzer, 312

Freeze, 31

Koeppen, 49

J e t e l , 67

Canter, 281, 319, 325 Kolkwitz, 79 m e n , 320, 323

Gilimeroth, 18

Cheney, 283

Goldschmidt, 55

Cherkasow, 178, 179

Gontcharow, 312

Korzun, 6

Kost j akov, 190 Kovda, 53 Chezy, 59, 60

Haeusner , 369

Kramer, 18

Hanke, 358, 360

KieEek, 279

Hargraeves , 180

Krefmer, 17, 279, 280, 1!82

Hart, 281

Kutilek, 14, 43, 174

COMECON, 148, 208

Costin, 289 Cowan, 32, 33 C r i t c h f i e l d , 50

379

Lamb, 270

Polynov, 53

V a l e n t i n i , 59

Laneel ier , 129

P o t t e r , 273

Viliulina, 12

Reijonen, 364

Wechmann, 17

Robinson, 31

Nhite, 13

Rode, 43, 44

WHO, 124, 125, 126

Rooseboom

Williams

Ianda, 27 Iane, 312 Law, 193 k g o s t a j ev , 196

Levi, 59 Wilson, 201, 298 Liebig, 77

Schamw, 339

Linsley, 22

Schaw, 146

h o w i t c h , 276, 285, 286

Schwabach, 284

Vitherspoon, 31 Wood, 159 Woodwell, 295 Schellenberger, 12 Maddock, 259, 260 Sermer, 12

Zeleni, 279

Shoemaker, 242

Zhukov, 97

Slsdezek, 79, 81

Zinke, 22

Maly, 307 Mason, 19 Maugh 11, 128

Meier, 47

Snyder, 370 Sokolov, 6 , 7

Minasian, 159 Sopper, 281 Moody, 250, 260 $rirnek, 82 Murzaev, 279 Stokes, 95 N a w n , 82

StraS krabova', 317

Neal, 56

Streeter-Phelps

, 96

Stumn, 129 Olsthoorn, 367 Sugawara, 36, 37 Orlob, 320, 323

Thienemann, 82 Pemberton, 311 'I'hornwaite, 44 P e m n , 14 Todd, 31 PeFina, 283 P h i l i p , 25, 26,

Uhlmann, 77, 78

P i t t e r , 296

USDA F o r e s t Service, 281

P l a t e , 253

US S a l i n i t y Lab., 186

380 SUBJECT INDEX

Abrasion 315

-

i n hydrological da ta 262-265

Accumulation e f f e c t 277

-

i n t h e inundated a re a 329

A e st h e t i c enjoyment 84

-

i n t h e r e s e r v o i r environment 329-330

Agricultural

Glow ing 41

-

Climatic drought 49

systems 169-171, 175, 182, 184

- y i e l d 172-179

C1ima to loqical functions 45-49

Albedo 3, 270 A l k a l i hazard 187

Climate 46, 49, 50, 73 Coe ffic ie nt of

Aquifer, 28, 31

-

Aquatic l i f e 324-328

- deoxygenation

Artificial

-

channel roughness 32 97-9 e f f i c i e n c y 111

- i n f i l t r a t i o n 367-368

- evaporation

-

- extension 105

p r e c i p i t a t i o n 371-372

- f i e l d e f f i c i e n c y 199

Balance - hydrological 5-6, 8-9, 224, 265-272

-

chemical 163

- e n e r p e t i c 3-5,

164, 269-270

- o f b e n e f i t s and expenses 356 - of water resources and needs 90,

22C-225

R i ochemical

-

156

c y c l e 50-53, 75 d i s i n t e g r a t i o n 9 8 , 317 d e v e l o p m m~171

-

he a t r e f l e c t a n c e 4 , 46

- diffusion -

69 i r r i g a t i o n e f f i c i e n c y 189, 191 permeability 212

- r e a e r a t i o n 06-98

-

re c yc ling 151 reduction 32 reflection 3 runoff 34, 36, 282-285 s o i l q u a l i t y 172 s t o r a g e 212

Biogeoelement 51, 53-55, 294-298 Biomass 71, 77-79

- tra nsm issivity 212 - t r a n s p i r a t i o n 178

Biosphere 4 , 7 1 , 324

- v a r i a t i o n 103 - water d e l i v e r y

Roiling w a t e r 157-160 Capacity

- optimum - 113 - m i s t u r e - h ol d i n g

190

189, 198

- water

loss 156

- water - total - yield

e f f i c i e n c y 199 178

requirements 177

Carcenogens 122

conjunctive use 363-365

Capital-turnover r a t i o 352

consumers 71

Catchment a r e a 8

consrunptive use 88-91, 180

Changes - i n f l u e n c i n g p r e c i p i t a t i o n 282

cost-sharinz method 256-258

c o s t of water 131, 138, 335, 358-361

381 C r i terium

Evapotranspiration 10, 13, 15-18, 43,

- of environmental p r o t e c t i o n 226

4 8 , 274

- of in-stream water u t i l i z a t i o n 227 - of withdrawal p r i o r i t i e s 227

Fairway 104-105

C r i t i c a l bottom

Financial a n a l y s i s 255-258

c u r r e n t v e l o c i t y 100

Fish occurrence 327-328 Floods 52

Degree of flood control 239

Flood control 240, 330

Delta f o r m t i o n 309

Flow control 239-245

Deposition 310

Flow

Depth of t h e fairway 105

- s a t u r a t e d 25

Desalination

-

Des t r a ti f i c a t i o n 324

- i n channel network 32 - overland 22-23

Destructors 71

unsaturated 25

Dew-point 48 Draught

FreiEht turnover 107

- admissible 104

Groundwater 25-50

Drinking water 121-136

- c l a s s i f i c a t i o n 67-68

Ecosystem 7 3 , 7 4 , 77 Economic optimization 255-258

-

Efficiency

- reserve

- f i l t r a t i o n 164

Guaranteed d e l i v e r y 213

- i r r i g a t i o n 189, 191

Guarantee r a t e 236-238

-

a q u a t i c 7 7 , 324-328

- flow 40, 66 fliictuation 31 p o t e n t i a l 29-30 recharge 35 runoff 37

- f e r t i l i z i n g 192

-

s a n i t a r y 193

- water

use 181

E l e c t r i c a l conductivity 70

FIomeos t a s i s 1 Hothouse e f f e c t 46 Tlydraulic conductivity 29-30, 4 Hydrologic

Energy

- cycle 4 , 8-10, 50, 71

- balance n a t u r a l 3 , 4 , 8 , 12 - balance i n i n d u s t r y 164

Hydrometeorological regime 262

-

FIyplimnion 319, 322

i n p u t 62

Hydrosphere 94

- r e f l e c t i o n 4 , 270 Epilimnion 319

Index of water managanent 232

Erosion 51-53, 55, 315 Eutrophization 99

Inland water t r a n s p o r t 103-111 I n t e r c e p t i o n 21, 22, 3 3 , 274

Evaporation 10-18, 3 3 , 3 6 , 46

I n f i l t r a t i o n 23-25, 3 3 , 40, 41,

-

Impact of

l o s s e s 155, 156, 203 r e d i s t r i b u t i o n 306 - suppression 369

27 5-27 7 - a g r i c u l t u r e 271-287, 292-297

, 212

-

f o r e s t r y 271-287

Multipurpose water u t i l i z a t i o n 257, 301

- i n d u s t r i a l i z a t i o n 287-292 - i r r i g a t i o n 305

Natural environment 1 , 303, 324

- r e s e r v o i r 303, 330

Non-conven t ional

Impact on - erosion and floods 277-281 - groundwater 282 - i c h t y o f a m a 327-328 - mesoclimate 306-309 - r a i n f a l l 282 - sediment t r a n s p o r t 309-313 - temperature 3 1 8-32 1 - water q u a l i t y 316

I n f i l t r a t i o n 23-25, 33, 40-41 Inland navigarion 103-111 Irrigation a n t i - f r o s t 195 f e r t i l i z i n g - 191-194 leaching - 195

-

techniques 218

- water

resources 222

Non-Lit i 1i z a b l e res e w e 2 19 N u t r i t i o n chain 97 Optimization 240, 254-256 Operating procedures 240 Oxygen - content 96 Oxygen demand - biochemical 69, 97, 102 - chemical 69 Parameters of watemay 103-106 Planning model 259-261

p r o t e c t i v e 194-195

P o l l u t i o n 29, 293-296 primary secondary -

remedi a1 191- 194 requirements 188

a i r - 293, 297-299 Specifj-c d a i l y 120

water q u a l i t y 185-187

Population equivalent 166

methods 189

Iake ecological model 323 Land c l a s s i f i c a t i o n 188 l a n g e l l i e r ’ s index 129 Law o f minimum 77 Local climate 46, 73 Lockage 107-111 Long-distance conveyance 361-363 W r g i n a l t r a n s p o r t d i s t a n c e 362 Metalimion 319 Microclima te 119, 307-308 N i n e r a l i z a t i o n 62, 316 Minimum discharges 225-229 Mixing formula 316, 333 Modelling 247-251 Monolimnion 319

Porosity

-

e f f e c t i v e 25, 40, 212

- t o t a l 25, 212

P r e c i p i t a t i o n 19-21, 33, 36, 49 Process - aerobic 97

-

anaerobic 97

Producers 71 Production process 77 Protection a g a i n s t floods 89 Protection of p i p e l i n e s 129 Rainfall-runoff process 36 Rate

- of - of -

guarantee 234-238 i n f i l t r a t i o n 25

of usage 231

383 Ratio ( o f ) - concentration - water consumption 151 - water l osses 152 - water re-use 149-150 - water surface 304 - withdrawals 232 - withdrawal u t i l i z a t i o n 152

sodiumadsorption 186 Raw water 127 Release - addi t i onal 240-243 Reservoir operation Reimbursement of expenses 356 Resulting u n i t m s s 316 Retention e f f e c t Return flow 90 River boards 341 River t r a i n i n 2 336-337 Routing of t he fairway 106 Runoff 33 - augmentation 368-371 - c o e f f i c i e n t 34, 282, 285 - groundwater - 26-32, 21 7-220 - intermediate - 37 - regul at or 46 - surface

-

34, 37, 217-220 - 35

- t o t a l annual

Safe y i e l d 213 S a l t tolerance 187 Sani t ary - admissible concentration 126, 296 - hazard 193 Sat urat i on 25, 63 Sediment - deposition 310-313 - t ransport 309, 339 Sedimentation 95-96 S e l f - p u r i f i c a t i o n 94-5, 99, 102 Sodium adsorption r a t i o 186

S oil - moisture 26, 42 - q u a l i t y 44, 61, 67-70, 79, 81 - regeneration 9, 336, 351 - water pote ntia l 30 - water regime 44 Storage - depression and detention - 22, 23, 33 - flood - 239 - reduction - 309-313 - underground - 363-365 Steam power water 157-160 Stokes law 95 S t o r a t i v i t y 212 Suffusion 41 System abiotic 1 a g r i c u l t u r a l 169 a na lys is 247 - biologic a l 1 cateffories closed-circuit - 146, 123, 145-148, 155 - de c is ion making 341

-

- economic - 252 - i n d u s t r i a l 144 - m d e l l i n g 247-252 - open-circuit 145-146, 155 - operation - optimization 253-254 - root

-

176

- socio-economic

1 steam 158 - successive re-use 146 - water management - 245-247

-

-

Thermal s t r a t i f i c a t i o n 318-324 Toxic matter 298 Transmissivity 212 Transpiration 46 Transport capacity 309 Trap e ffic ie nc y 312

384 Trophicity 79 Was t e - f r e e technologies 167-169 - disposal 94-101 Waste water 90, 94, 144, 147, 191-194 - - categories 296 - - not s u i t a b l e f o r recycling Ib6 - - re-use and recycling 165 Water - c i r c u l a t i o n r a t i o 10

-

-

consumption 88-93, 149-152, 159, 181 conveyance 361-363 cooling - 15ii-157 development stages 211 d i l u t i o n - 120 drinkine - 121-136

- entering the product 145

feed - 158-159 Water losses 88, 93, 110 - i n industry 145, 149-151, 160-165 Water management - a c t i v i t i e s 343 - function of f o r e s t s - organizations 342 - paradoxes 344-346 - policy 92, 341 products 353 services 354 strategy 346-350 t a c t i c s 351 Water metering 142 - mining 152-153 - needs 221 - occurrence 1, 7 , 88, 212 - pollution 70, 98, 111, 207-210 - pollution indicators 70, 102, 186, 22 1 - power 111 - pricing 138, 335, 358-361

-

quality 100, 224

- rates

131, 355, 358-361 - recreation 115-120 - recycling 150-160 k t e r requirements 88, 92, 220-222 actual - - 175, 180 a g r i c u l t u r a l - - 171 domestic - - 130 f i r e extinguishing - - 136 - 138 i n l m d navigation - - 109 livestock 204, 208 lockage 108-111 maximum - - 141, 207 minimum - - 92, 141 municipal - - 120-139 - - per capita and day 131-135 - - per u n i t of production 152 physiological - - 122, plant - - 173-180

-

processing - - 153-155 rural - - 120-139 urban public - - 134-189 raw - 127 re-use 133, 144-152 saving 92, 110, 133 steam power - 157-160 supplementary - 158, 161, 163 supply 8 , 86, 88 transport 103 treatment 127-128, 153-154, 158

- use 86, 93 - - in-stream 86, 87, - - on-site 86, 93

93

Water users 86 Water uses - - non-conventional Warm - 130 Mater wastage 132, 141-142 Waterway c l a s s i f i c a t i o n 104 Water withdrawal 86-88

385 Yield - agricultural - 172-179 - economically utilizable - 217 - maximum sustained - 214 - mining - 214, 218 - natural - 215, 217 - permissive sustained - 214 - theoretical - 215, 217, 218 - technically utilizable - 215

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