SM
IWMI is a Future Harvest Centersupported by the CGIAR
Hydronomic Zones
for Developing Basin Water
Conservation Strategies
RESEARCH
56
Water ManagementI n t e r n a t i o n a l
I n s t i t u t e
David J. Molden, R.Sakthivadivel and Jack Keller
R E P O R T
SM
IWMI is a Future Harvest Centersupported by the CGIAR
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ISSN 1026-0862ISBN 92-9090-463-1
Water ManagementI n t e r n a t i o n a l
I n s t i t u t e
Research Reports
IWMI’s mission is to improve water and land resources management for food,livelihoods and nature. In serving this mission, IWMI concentrates on the integrationof policies, technologies and management systems to achieve workable solutions toreal problems—practical, relevant results in the field of irrigation and water and landresources.
The publications in this series cover a wide range of subjects—from computermodeling to experience with water user associations—and vary in content fromdirectly applicable research to more basic studies, on which applied work ultimatelydepends. Some research reports are narrowly focused, analytical and detailedempirical studies; others are wide-ranging and synthetic overviews of genericproblems.
Although most of the reports are published by IWMI staff and their collaborators,we welcome contributions from others. Each report is reviewed internally by IWMI’sown staff and Fellows, and by external reviewers. The reports are published anddistributed both in hard copy and electronically (www.iwmi.org) and where possible alldata and analyses will be available as separate downloadable files. Reports may becopied freely and cited with due acknowledgment.
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Research Report 56
Hydronomic Zones for DevelopingBasin Water Conservation Strategies
International Water Management InstituteP O Box 2075, Colombo, Sri Lanka
David J. MoldenR. SakthivadivelandJack Keller
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IWMI receives its principal funding from 58 governments, private foundations, andinternational and regional organizations known as the Consultative Group onInternational Agricultural Research (CGIAR). Support is also given by the Governmentsof Pakistan, South Africa and Sri Lanka.
The authors: David J. Molden is a Principal Researcher and Coordinator of ComprehensiveAssessment of Water Management in Agriculture, R. Sakthivadivel is a PrincipalResearcher and Jack Keller is a Consultant, all of the International Water ManagementInstitute Colombo, Sri Lanka.
Molden D. J.; J. Keller; and R. Sakthivadivel. 2001. Hydronomic zones for developingbasin water conservation strategies. Research Report 56. Colombo, Sri Lanka:International Water Management Institute.
/ water conservation / river basins / case studies / irrigation / water management / wateruse efficiency / Sri Lanka / India / Egypt / Turkey /
ISBN 92-9090-463-1
ISSN 1026-0862
Copyright © 2001, by IWMI. All rights reserved.
Please direct inquiries and comments to: [email protected]
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Contents
Summary v
Introduction 1
Hydronomic zones 1
Description of zones 3
Conditions within zones 7
Formulating water conservation strategies for basins 7
Case studies 12
Lessons from case studies 23
Discussion 24
Summary and conclusions 26
Appendix 27
Literature cited 29
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v
Summary
In this report, the concept and procedures ofhydronomic (hydro water + nomus management)zones are introduced. A set of six hydronomiczones are developed and defined based on keydifferences between reaches or areas of riverbasins. These are the: Water Source Zone,Natural Recapture Zone, Regulated RecaptureZone, Stagnation Zone, Final Use Zone, andEnvironmentally Sensitive Zone. The zones aredefined based on similar hydrological, geologicaland topographical conditions and the fate of wateroutflow from the zone. In addition, two conditionsare defined which influence how water ismanaged: whether or not there is appreciablesalinity or pollution loading; and whether or notgroundwater that can be used for utilization orstorage is present. Generic strategies for irrigationfor four water management areas, the NaturalRecapture, Regulated Recapture, Final Use, andStagnation Zones, are presented. The Water
Source Zone and Environmentally Sensitive Zoneare discussed in terms of their overall significancein basin water use and management.
Hydronomic zones allow us to define,characterize, and develop managementstrategies for areas with similar characteristics.The concept of zoning is demonstrated in fouragricultural areas representing a wide variety ofsituations: the Kirindi Oya basin in Sri Lanka,Egypt’s Nile basin, the Bhakra command area inHaryana, India and the Gediz basin in Turkey.We were readily able to apply the zones withineach basin and suggest water managementstrategies for each zone. Hydronomic zones holdpotential as a tool to help us better understandcomplex water interactions within river basins, toisolate similar areas within basins and to help usdevelop sets of water management strategiesbetter tailored to different conditions withinbasins.
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Hydronomic Zones for Developing basin waterConservation Strategies
David J. Molden, R. Sakthivadivel, and Jack Keller
Introduction
All terrestrial freshwater use takes place within abasin context. Within each basin, there arehydrological, topographical, and hydrogeologicaldifferences between areas or reaches, requiringdifferent water management and conservationtechniques. Unfortunately, too often this is notdone and the same water managementstrategies are employed without consideration tocharacteristics of different parts of a basin.
Our objective is to provide a simpleframework to visualize water use in a basin andenable formulation of effective, site-specific,
water management strategies. This paperdefines hydronomic (hydro water + nomusmanagement) zones, describes conditions thatmay occur within zones, and presents genericwater management strategies for the mainzones. We hypothesize that a generic set ofzones and strategies can be developed tocharacterize a variety of situations found in riverbasins. To test the hypothesis we applied theseconcepts to the Kirindi Oya basin in Sri Lanka,Egypt’s Nile basin, the Bhakra irrigation systemin Haryana, India, and the Gediz basin in Turkey.
Hydronomic Zones
Let us illustrate hydronomic zones with a simpleexample, washing hands. We turn on the tap,apply water and soap, then rinse off the soap.Some people may use the water quite frugally,while others may enjoy the process and spendseveral minutes savoring the water running overtheir hands. Given that water is an increasinglyscarce resource, the question should arisewhether or not the person is conserving water.The answer is found by considering whathappens to the water after the hands are washed.
Some water remains on the hands, and iseventually evaporated, while the rest remains asa liquid, picks up some soapy material andpasses into a drain. In many cases, the drainage
water finds itself back to a river, is mixed withriver water, and can be again diverted for anotheruse. In other cases, the drainage water flows tothe sea and cannot be reused, or it is not soeasily drained and contributes to groundwaterbuildup and waterlogging. In the first case, fromthe point of view of water savings, we are not soconcerned about using a high quantity of watersince it is readily available for reuse. We may beconcerned about the costs of delivery of water,and may wish to reduce the use of water tocurtail costs of treatment and delivery. In thesecond case where water is not readily reused,we would be quite concerned about the amountof water applied to the hands.
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Whether the water use is washing hands,industrial cleaning, or irrigation, it is useful toconsider where the drainage water flows, andthis is the essence of the concept of hydronomiczones. Hydronomic zones are defined primarilyon the destiny of drainage outflows from wateruses. Two basic conditions are presented infigures 1a and 1b:
1. Situations where outflow can be reused.
2. Situations where outflows cannot be
reused because of location or quality of
water.
Whether we are in condition 1 or 2 dependson our geographic location in the river basin. In
its simplest form, we have two hydronomiczones. We will expand this concept further tosix zones (figure 2), then include the possibilitiesof groundwater storage, and implications ofpollution. When discussing real water savingsopportunities, we will focus on irrigatedagriculture, and outline irrigation strategies forthe various zones.
Figures 1a and 1b represent two basichydronomic zones. In figure 1a, as a result of awater use, part of the water is converted toevaporation or transpiration. The remaining flowsdeparting the hydronomic zones are utilizable,and could be again put to use by a downstreamuser. In figure 1b, the outflows go to a sink, orbecome too polluted to be reused bydownstream users.
FIGURE 1a.
Outflows recoverable.
FIGURE 1b.
Outflows non-recoverable.
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Description of Zones
The following description of the six hydronomiczones begins with zones where most watermanagement and irrigation efforts are focused:the Natural Recapture, Regulated Recapture,Final Use, and Stagnation Zones. Then wedescribe the Water Source and EnvironmentallySensitive Zones—zones that require carefulconsideration when considering a basin’s watermanagement programs. The concept ofhydronomic zones evolved from a work originallyperformed in Egypt where the Nile was dividedinto Water Management Strategy Zones, andvarious strategies developed for each zone(WRSR 1996a; WRSR 1996b). The authorsrecognized that this concept had generic value,and with some expansion, could be applied andwill be useful for most basins in the world.
Natural Recapture (NR) Zone. The NaturalRecapture Zone is the reach or area of the basinwhere surface and subsurface drainage waterbecome return flows that are naturally capturedby river systems or channel networks. In thiszone, rivers act as a conveyance channel forwater and also serve as the main drain. Theportion of water that is diverted but not depletedby evaporation in a given use cycle is naturallyrecaptured and available for reuse. There islittle opportunity to manage the mixing and reuseof drainage water. For example, in the uplandhills, valleys and alluvial benches along riversand their tributaries, water is diverted forirrigation or other uses and the drainage oroutflow returns to the same river. Throughoutthe Natural Recapture Zone the system is self-
FIGURE 2.
Hydronomic zones in a river basin.
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conserving because the drain and seepage flowsnaturally return to the water supply distributionsystem (without being pumped).
An example of the Natural Recapture Zoneis the irrigation diversions in the hills of Nepalwhere the seepage and runoff flows back to theriver system and are readily tapped downstreamand reused. Another example is the Nile rivervalley in upper Egypt where outflows fromirrigated service areas supplied with Nile waterend up as seepage flows or in drainage canalsthat drain back into the river. Thus the Nile riverserves as both the main supply and maindrainage channel and the drain flows arenaturally recaptured (without pumping). A thirdexample is the Tambraparani system in SouthernIndia (Brewer et al. 1997) where a series ofdiversion structures (anicuts) supply water toirrigation through contour canals. The drainagefrom irrigation application returns to the river, iscaptured by the anicuts, and used again anumber of times through drainage, recapture,and reuse.
Regulated Recapture (RR) Zone. A RegulatedRecapture Zone is any reach or area of thebasin where the reuse of surface runoff, spills,drainage, seepage or deep percolation water canbe regulated. Return flows are captured by adrainage network that is physically separate fromthe distribution network and water does notnaturally return to the river. Therefore, physicallinkages must be built and operated to facilitatethe reuse of the portion of water that is divertedand not depleted by evaporation in a given usecycle. This situation is advantageous becausethe reuse can be managed for quality as well asquantity control. In some parts of the Regulated
Recapture Zone gravity diversions on the drainscan be employed to raise the water levelsufficiently for irrigation reuse, while in otherparts of the system pumps must be employed tolift the water from drains or from groundwatersupplies.1
Typically, Regulated Recapture Zones arethe irrigated areas in the upper reaches of riverdeltas adjacent to coastal plains. If the drainageand groundwater flows are not captured they willflow to the sea. Other Regulated RecaptureZones are found in areas where groundwater isextensively used such as the North China Plains,or the Punjab (in both India and Pakistan). Inthese cases, pumping groundwater is a means ofrecapturing percolation water. An example of theRegulated Recapture Zone is the upper three-quarters of the Egypt’s Nile delta. There, thedrains are separated from the canal distributionsystem. Wells are used in the uppermostreaches to recapture and supply water for use inmunicipal water supplies. Gravity diversions areused along the drains or river branches to re-divert water into irrigation canals in the middlereaches and large, medium and small scalepumping is necessary to lift water for reuse inthe lower reaches. Another example ofRegulated Recapture Zones can be found ininnumerable scattered tanks interspersed withsurface irrigation systems of South India and SriLanka to capture surface runoff and drainage,and to supplement canal water supplies.
Final Use (FU) Zone. A Final Use Zone is anyreach or area of the basin where there is nofurther opportunity for downstream reuse. Thewater in the drains is of little or no value inproductive uses. This zone is typically situated
1Where the drainage networks are permanently tied back to the canal distribution system there is no opportunity for regulating the reuse, thatportion of the Regulated Recapture Zone in effect becomes part of the Natural Recapture Zone. In such cases the system is self-conservingbecause the drain and seepage flows naturally return to the water supply distribution system (without being pumped).
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at the terminal end of the basin adjacent to itssalt sink(s); its quality is too low for irrigatingstandard crops or there is no opportunity forreusing outflows from this zone. For example,even if return flows are of good quality, theremay not be capacity to store water—or thequantity of water may be in excess of what canbe depleted by the downstream area, andwould thus flow to a sink. Final Use Zonesmay fall adjacent to Environmentally SensitiveZones described below, in which caseecological requirements are a strong concern.
Final Use Zones fall at the end of basinssuch as the lower delta in Egypt, the lowerportions of the Muda irrigation system inMalaysia, and the tail end of the Menemenbasin in Turkey. Outflows may be required toremove pollutants or to maintain environmentssuch as coastal lagoons, mangrove forests, orestuaries. Salt water intrusion is often an issuein the Final Use Zone. Final Use Zones mayalso be situated inland in open basins wherethere is no infrastructure capacity to reusedrainage water from the Final Use Zone. Forexample, areas that drain into the lowerportions of the Yangtze river, or lower portionsof the Ganges river are also Final Use Zones,because a reduction in drainage from the FinalUse Zones (up to a certain extent) in thesesituations would not be of concerndownstream.2
Where the Final Use Zone is adjacent tothe Regulated Recapture Zone, there is often atradeoff between having a more relaxed systemallowing drainage and reuse or having a verytight system with little or no excess water, andlimited opportunity for reuse. For example, one
strategy to reduce drainage flows would be tohave a narrow Final Use Zone, with intensivereuse upstream of the Final Use Zone, and veryprecise delivery and application techniqueswithin the Final Use zone. Another approach isto have a broad Final Use Zone with highlyefficient water use but limited reuse upstream.Thus, the size and shape of the Final Use Zoneand Regulated Recapture Zone are a function ofthe infrastructure and management practiceswithin these zones. The combination of thesezones is referred to as the Closure ManagementArea. In closed basins, this is where there isthe greatest opportunity for obtaining real watersavings by recapturing or reducing canaloperational spills and field application lossesthat would otherwise discharge into the basin’ssalt sink(s). It is within the ClosureManagement Area that we carefully examine thetradeoffs in terms of water quality, quantity andcosts between precise irrigation practices andallowing more reuse.
Stagnation (S) Zones. A Stagnation Zone isany isolated area where the drainage capacityis insufficient for the removal of leached saltsand excess water. Stagnation Zones arecharacterized by rising water tables,waterlogged and/or salinized areas. StagnationZones often occur in areas of salinegroundwater, in areas where drainage waterpasses through soils naturally containing salts,in dead-end or depression areas, or in areaswhere surface drainage flows are mixed withsaline or polluted surface drainage water. In thiscase surface or subsurface flows are not readilyrecoverable.
2In other words, present flows in these rivers are more than adequate to meet downstream requirements. A reduction or increase in drainagefrom the area would have little or no effect on downstream uses. However, if downstream uses increase such that downstream uses becomeadversely affected, the basin begins to close, and the Final Use Zone would have to be reclassified as a Regulated or Natural RecaptureZone.
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Examples of Stagnation Zones occurthroughout the Indus basin in Pakistan and innorthwest India that have depressions or pocketsof saline shallow groundwater. There are isolatedareas along the fringes or outer irrigated edgesof (and also within) Egypt’s Nile valley and deltawhere drainage waters are quite saline and thesoils are becoming salinized. In these areaswhere there is inadequate drainage, excessiveuse of surface and reuse of drainage water andgroundwater results in waterlogging, salinizationand decreasing yield due to secondarysalinization.
Water Source (WS) Zone. In a Water SourceZone, excess precipitation provides runoff orgroundwater recharge for downstreamprocesses. It is the area of the catchment wheremost of the runoff or water supply originates. Anisolated aquifer may also make up a WaterSource Zone where mining of this water takesplace, as in the Western Desert of Egypt. Wehave delineated this zone because this is ofprimary importance in the formulation of a watermanagement program for a river basin. Therunoff coefficient or water yield as a proportion ofthe precipitation on the basin and its sedimentload are dependent on how the Water Sourcearea is managed. Water harvesting andsupplementary irrigation may take place in thiszone.
Management strategies in the Water SourceZone can affect basin-wide water use. Forexample, in many basins, relatively smallpercentage increases in runoff can greatly affectthe amount of water available for irrigation orother uses. Also in the Water Source Zone,
there are opportunities to capture and userainfall locally through water harvesting. Whenconsidering these options, basin-wide tradeoffsmust be considered. For example, decreasingforestation to increase yield may increasesediment loading. On the other hand, practicesto decrease sediment loading often alsodecrease water yield.
Environmentally Sensitive (E) Zone. AnEnvironmentally Sensitive Zone is any areawhere there is a requirement of water forecological or other environmentally sensitivepurposes. For example, changes in quality orquantity of drainage flows from irrigation mayadversely affect wetlands, thus wetlands areclassified as Environmentally Sensitive Zones.Other examples include reaches of rivers thathave minimum flow requirements, navigationrequirements, or even special urban orindustrial requirements. When developinghydronomic zones, it is very important todelineate these environmentally sensitive areasso that future programs will carefully considertheir needs.
Formulating water management programsfor Water Source and Environmentally SensitiveZones requires special multidisciplinary efforts.We are describing the Water Source andEnvironmentally Sensitive Zones to ensure thatthey are sufficiently considered. At a futuredate IWMI (International Water ManagementInstitute) will develop the methodology forformulating water management programs for theWater Source and Environmentally SensitiveZones of river basins where irrigated agricultureis of importance.
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Conditions within Zones
Two basic conditions within hydronomic zonesshould be considered when characterizing abasin: pollution and salinity, and existence ofgroundwater.
Pollution or salinity loading
Here we will consider two cases, pollution/salinityloading (p/s), and no appreciable pollution orsalinity loading (np/s). An area loads the basinwith pollution or salinity if an additional mass ofpollution is added to the basin through theoutflow from the area of interest. An example isthe leaching of residual salts as a result ofirrigation. Another example is a river reachwhere cities and industries pollute waterwaysand affect downstream uses.
Groundwater storage/utilization
Freshwater aquifers underlying irrigated areassupport two important functions. One function isto temporarily store and convey water. This iscommon in irrigated areas where deeppercolation enters the groundwater, is kept forsome time, then pumped out at a different
location. The second function is to providelong-term storage to balance deficits andsurpluses of surface inflows and precipitationover seasonal, annual or even multi-yearperiods. The current or potential degree ofdependence on and utilization of groundwaterstorage is an important consideration informulating water management programs. Inview of this we will consider three groundwatersituations. No appreciable groundwaterdependence (nGW), groundwater utilizationfocused on recapturing and distributing water(GWD), and groundwater utilization focused onwater storage as well as recapturing anddistributing water (GWS).
In GWS areas there is always the danger ofover pumping and mining the aquifer. Wherethis is the case the long-term usage of thegroundwater will be unsustainable, and the depthto the water table and consequent pumping liftswill become excessive and eventually thegroundwater resource will be economically if notphysically depleted. In coastal areas there isalways the threat of saltwater intrusion from thesea, which is an insidious problem that may beundetected for a considerable time andeventually completely salinize the aquifer.
Formulating Water Conservation Strategies for Basins
Final Use, and Stagnation Zones with specialattention given to the Closure Management Area.
Typically, the Natural Recapture andRegulated Recapture Zones not underlain withsaline groundwater are considered NaturallyConserving Areas when pollution in return flowsis minimal. In these zones, water that is notdepleted in a given use cycle will readily beavailable for reuse downstream. Because canal
The primary reason for separating basins intodifferent hydronomic zones is because eachzone has its own “best set of water-savingstrategies.” Strategic research and designactivities are needed to formulate packages ofactions to implement in each of the zones. Inthis paper, we will focus on water savings inirrigated agriculture. Thus our focus will be onthe Natural Recapture, Regulated Recapture,
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3In open basins, more water could be developed and beneficially depleted upstream without diminishing existing uses: in other words, theopportunity cost of additional depletion is zero. A closing basin has no more remaining available water flowing out of the basin during part ofthe year, typically a dry season. In a completely closed basin, all water is committed to environmental and process uses.4For example: whether the area is pollution or salt loading (p/s) or not (np/s), or whether there is appreciable groundwater dependence forstorage (GWS) or distribution (GWD) or not (nGw).
5In a different type of water accounting effort, Molden and Sakthivadivel (Molden 1997; Molden and Sakthivadivel 1998) developed termscalled Process Fraction (PF) and Beneficial Utilization (BU). These terms relate intended or Beneficial Utilization to the water available foruse within a field or irrigation system. These terms are similar to CE, but are especially useful in situations where rainfall on irrigated areas isan important supply for cities, industries, or environmental uses where irrigation efficiency does not apply. For simplicity we will use the ClassicalEfficiency formulation in the discussion, but the discussion would remain the same if Process Fraction or Beneficial Utilization were used.
operation and field application losses arerecaptured and available for reuse downstream,irrigation improvements in these zones will resultin little real water savings. But, someimprovements in these zones may be warrantedon grounds of providing water-short areas withbetter access to water and increased productionper unit of water consumed by cropevapotranspiration.
Formulating Strategies
Our procedure for formulating water managementstrategies for each of the hydronomic zonesinvolves first considering whether the basin isclosing, closed or open3 (Seckler 1996; Keller etal. 1998). Then for each zone we consider thestatus of pollution/salt loading and groundwaterstorage/utilization.4 While this may appear toresult in a large matrix of water managementstrategy possibilities, it can be quickly narroweddown to a practical set of possibilities. First ofall, determination of whether the basin is open orclosed greatly reduces the number ofpossibilities. The Stagnation Zone stands alonebecause the package of strategies for StagnationZones are generally quite site specific.
Local and Basin Considerations
One common misperception is that increases inirrigation efficiency will lead to water savings at abasin scale to alleviate problems of water
scarcity and competition (Seckler 1996). Insome cases, increases in efficiency do lead to“real” water savings, where saved water can betransferred to an additional use. In other cases,this is not the case, and increases in efficiencydo not lead to real water savings. Hydronomiczones help to clarify the issue of when efficiencyincreases lead to increased beneficial utilization,and when they do not.
At the scale of a particular service or use,like an irrigation system, city, or irrigated fields,expressions of local efficiency have beendeveloped. Mathematical expressions ofirrigation efficiency generally take the form ofcrop evapotranspiration (ET) less effectiveprecipitation divided by diversions to irrigation,and is referred to as classical irrigation efficiency(CE) (Keller and Keller 1995):
CE = (ETa – Pe)/DIV
Where ETa is the actual crop evapo-transpiration, Pe is the effective precipitation,and DIV is the diverted water from surface orgroundwater.
Various versions or refinements of thegeneral form of CE have been presented(Israelson 1932; Bos and Nugteren 1974; Burt etal. 1997). Classical Efficiency is higher whenETa increases or when diversions decrease. Adisadvantage of this formulation is how rain ishandled. Classical Efficiency formulationssubtract out effective rainfall in the numerator,leaving the focus on water diversions.5
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TABLE 1.
General guidelines for determining when it is appropriate to increase Classical Efficiency.
If CE is 40 percent, is the other 60 percenta loss? This depends on what happens to thereturn flows (the flows that are diverted but notdepleted by crop evapotranspiration). We knowthat in many instances return flows areavailable for other beneficial uses downstreamand do not necessarily represent a loss. Ingeneral, there are 3 situations defined byhydronomic zones useful for deciding whethera high Classical Efficiency is warranted (table1). The appendix ( page 27) gives morespecific means of increasing CE.
General Strategies by Zone
Consideration of water flow paths helps informulating strategies for saving water. The zonestell us where water can be allowed to flow, andwhere water should not be allowed to flow. Forexample, in the Final Use Zone, drainage outflowsin excess of environmental requirements should berestricted in closed and closing basins. Strategiesto achieve real water savings are summarized inBox 1 giving consideration to flow paths andClassical Efficiency.
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BOX 1.
Matching irrigation strategies with zones and conditions within zones.
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BOX 1. Continued.
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Case Studies
In this section, we present four case studiesfrom various situations to demonstrate the use ofhydronomic zones. For each case we provide abrief description of the basin plus a map showingthe hydronomic zones. Then based on thezoning, we suggest various water managementstrategies that could improve water use in thesebasins.
Kirindi Oya Basin in Sri Lanka
The Kirindi Oya river basin in southern Sri Lankaflows from the medium range hills of Sri Lankato the Indian Ocean (figure 3). Water resourcesin the area have supported vigorous agriculturesince ancient times (Brohier 1934). The YodaWewa, Debera Wewa, Tissa Wewa, Weerawila,Pannagamuwa and Badagiriya tanks utilizeKirindi Oya water for irrigation and other uses(Bakker et al. 1999). This area is referred tohere as the Old Area served by the old tanks.The Kirindi Oya Irrigation and Settlement Projectprovided irrigation upstream of this old area fornew settlers with the addition of theLunugamvehera reservoir, which began operationin 1985 (IIMI 1995). The additional landsirrigated by the project are referred to as theNew Area.
The basin is considered closing becauseduring parts of the year there are only verylimited outflows to the Indian Ocean. During thewet seasons, there is utilizable outflow to theIndian Ocean through drains and the river inexcess of environmental requirements. Thisoutflow represents a real water savingsopportunity. Except during wet periods, anincrease in upstream depletive use would affectdownstream uses of water. Occasionally, floodflows occur resulting in water spilling from thereservoir to the Kirindi Oya and to the sea.There is no appreciable salinity or pollutionproblem. While groundwater use is an important
economic activity, the potential use ofgroundwater as a storage and regulatingreservoir is not significant in terms of the volumeof water.
The following zones are identified at KirindiOya:
• Water Source Zone (WS): Beginning inthe upstream area is the Water SourceZone. Upcountry plantations and forestsoccupy this area.
• Natural Recapture Zone (NR): Movingdownstream is a Natural RecaptureZone, surrounded by Water Sourceareas. Here there are several smalltanks serving irrigated farmers.Recently, many open wells and river liftpumps have been developed privately byfarmers for vegetable growing. Withincreased population in the area, landuse is rapidly changing. Any increase inevaporative depletion in this regionresults in a decrease in water availabilitydownstream. Drainage outflows fromvarious uses naturally find their wayback to the Kirindi Oya where there isopportunity for reuse downstream.Eventually, they flow into theLunugamvehera reservoir where they willbe again diverted.
• Regulated Recapture Zone (RR): TheRegulated Recapture Zone shown infigure 3 lies between the Lunugamveherareservoir and the old tanks (reservoirs).Return flows are captured by drains andtanks separated from the river, and thereare ample options for reuse. The oldtanks serve as storage and regulatingreservoirs, capturing upstream spills,storing them temporarily and providing asupply for downstream uses. Within the
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FIGURE 3.
Kirindi Oya River Basin.
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irrigated area are several trees, manythat are economically important such ascoconut trees, thriving on water indirectlysupplied by irrigation via the shallowgroundwater system (Renault et al.2000).
• Final Use Zone (FU): Downstream ofthe old tanks, and adjacent to the sea, isthe Final Use Zone. There is noopportunity for reuse of drainageoutflows downstream of this area. Thereare patches of salinity, especially in thenewly developed area where salts information have not been leached out.There is significant drainage outflow fromthis area, especially during the wetseason, and apparently there is scopefor real water savings in this zone.
• Environmentally Sensitive Zone (E):The lagoons incorporated in the Bundalanational park, downstream of theBadagiriya tank, constitute an importantecological use of water and are sensitiveto upstream, especially irrigation, wateruse. While some water is required todilute the sea water for brackish waterconditions, it is now thought that excessdrainage flow induced by irrigation isartificially lowering salinity levels andadversely affecting the existing ecology(Matsuno et al. 1998).
Water Conservation Strategies
Many consider this a water-short area becauseduring certain times of the year people do notreceive sufficient water for agricultural anddomestic needs. Water accounting studies inthe area show that there is considerable dryseason drainage outflow to the Indian Ocean thatcould be productively depleted by irrigation orother use (Renault et al. 2000; van Eijk et al.1999). Present investigations (Matsuno et al.
1998) show that excess irrigation drainagechanges the natural ecosystem in Bundala parkby lowering salinity levels. It has beenhypothesized that more upstream irrigationdepletion would result in less drainage to thepark, and thus be beneficial to this area.
There are certainly opportunities for realwater savings below the Lunugamveherareservoir to be found in the Final Use andRegulated Recapture Zones. Direct deliveriesfrom the Lunugamvehera reservoir to tanks andfarms in the Old Area (the Final Use Zone) couldbe substantially reduced or eliminated. Uses inthe old area would then rely on “reuse” waterfrom the old tanks.
Substantial savings could be found in theClosure Management Area consisting of theRegulated Recapture Zone and the Final UseZone. Within the Regulated Recapture Zone,diversion and pumping facilities could beemployed to recycle water. In fact, this is nowbeing increasingly practiced at Kirindi Oya withpositive results. By doing so, the RegulatedRecapture Zone is growing while the Final UseZone is shrinking. Classical Efficiencyimprovements in the Final Use Zone wouldreduce the water requirement and relateddrainage outflows. For example, when irrigatingrice, alternating wet and dry irrigation (Guerra etal. 1998) would reduce application requirementsand drainage outflows. Plus, more effective useof rain on farms, by increasing bund height incombination with a reduction in standing waterlevels on fields, could also reduce the need fordeliveries to farms. Water saved by thesepractices could be stored in the reservoir for usein the dry season, or alternatively, morebeneficial depletive use could be practicedupstream of the reservoir.
Changes that seem somewhat obvious aredifficult to implement because they requiresignificant changes in current perceptions andincentives. For example, downstream users inthe Old Area perceive that they have a first rightto water because they were the first to settle
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there. As a result, water is often delivereddirectly from the Lunugamvehera reservoir to thisarea first. This practice prohibits savingsopportunities that could occur if water could firstbe delivered to the New Area, with downstreamold tanks capturing return flows. Old Areafarmers would have to be convinced that theirneeds would be met with new water savingspractices to readily accept changing from theirexisting practices.
The Kirindi Oya case demonstrates howdifferent water conservation strategies in differentzones are required to overcome water scarcityand to maintain the natural ecosystem.
Egypt’s Nile
Almost all economic activity in Egypt is situatedaround the river Nile, the main source of waterfor the country. Figure 4 shows the Nile riverbelow the High Aswan dam. The Nile spreadsout into the Nile delta, then water dischargesthrough the river branches and drainage networkinto the Mediterranean Sea. Most water isdiverted to agricultural uses, but domestic andindustrial uses also rely on the same source ofwater (see WRSR 1996a; WRSR 1996b;Elarabawy et al. 1998; Molden et al. 1998 formore detailed descriptions of water use).Significant environmental requirements exist atthe northern end of the delta where there areimportant lakes, lagoons, and coastal estuaries.The Nile is rapidly closing, and unless anadditional supply of water is identified, additionalwater to meet growing agricultural, domestic andindustrial needs must come from real watersavings, primarily in agriculture.
The Nile can be divided into five zones(figure 4).
• Natural Recapture with GroundwaterDistribution (NR with GWD): TheNatural Recapture Zone is situated inUpper Egypt. There is no appreciablesalinity loading, but pollution loading,mostly from industrial and domestic usesexists. There are opportunities forgroundwater pumping. Drainage waterfrom all uses naturally drains back intothe river Nile or enters a groundwatersystem connected to the river.Improvements in Classical Efficiency inthis zone will not lead to real watersavings, because drainage water isavailable for reuse downstream.
• Regulated Recapture withGroundwater Storage and Regulation(RR with GWS): The RegulatedRecapture Zone is situated in the upperportion of the Nile delta. In this areathere is no appreciable salinity loading,although effluent from cities andindustries pollutes the water. There isample opportunity for conjunctivemanagement with groundwater storageand diversions, and there is intensiveuse of groundwater. This area iscovered by an intensive drainagenetwork, and there is substantialdrainage reuse both through largedrainage water reuse facilities and byindividual or small groups of farmersoperating small pumps. There is atradeoff between drainage water reuse,groundwater use, and surface water use,and many farmers use several sourcesof water. Increases in ClassicalEfficiency will decrease drainageoutflows to surface drains andgroundwater, and thus decrease theopportunities for reuse. Costconsiderations of various approaches isa more dominant consideration than realwater savings.
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Figure 4.
Nile River Basin.
• Regulated Recapture withGroundwater Storage and Regulationand appreciable Pollution and SalinityLoading (RR with GWS and p/s).Roughly in the middle of the Nile delta,there is increasing salinity. There areopportunities in the Regulated RecaptureZone for mixing fresh water and salinewater for agriculture, but using salinedrainage water alone would have to be
done with great care to sustainproductivity.
• Final Use with Pollution and SalinityLoading (FU with p/s). The Final UseZone is located at the tail of the Niledelta system where drainage outflowsare directed to the sea. There areimportant salinity and pollutionconsiderations in the area including
17
saline intrusion into groundwater (Amerand Sharif 1996). There are importantenvironmental considerations at theNorthern Lakes and the coastalestuaries. Classical Efficiencyimprovements accompanied by additionaluse elsewhere in the river system willresult in real water savings.
• Environmentally Sensitive (E) Zone.At the tail end are the Northern Lakesand coastal estuaries of ecological andeconomic importance. Livelihoods offishermen are dependent on good qualitywater, and the lakes serve importantecological functions. At present these areseverely affected by pollution fromupstream industrial, urban, andagricultural uses (Imam and Ibrahim1996). Conservation plans need toconsider the quality and quantity ofenvironmental needs in these areas.
Water Conservation Strategies
Within the Natural Recapture Zone, increases inClassical Efficiency will not lead to basin scalereal water savings. It will only lead to a changein water flow paths. Without Classical Efficiencyimprovements, water will be diverted from theNile to irrigated fields, then drain back to theNile. By reducing diversions from the Nile, waterwill remain in the river. Both options haveassociated economic and environmental tradeoffsfor consideration, but both options areapproximately equal with regard to the amount ofwater freed up for urban or further agriculturaluse. Within the Regulated Recapture Zone, thereis ample recycling of water. Increases inClassical Efficiency may or may not have othersocial or economic benefits, but again, will notlead to real water savings because of the extentof reuse.
Most opportunities for real water savings liewith the Closure Management Area—the lower
part of the Regulated Recapture Zone plus theFinal Use Zone. There are several possiblestrategies for water savings within the ClosureManagement Area summarized in Keller et al.1996a; Keller et al. 1996b; WRSR 1996a;WRSR 1996b. One option is to enlarge theFinal Use Zone through Classical Efficiencyimprovements in the Final Use Zone. In thiscase, diversions to the area and drainageoutflows would be minimized just to meetdownstream ecological commitments. Anotheroption would be to expand the RegulatedRecapture Zone, taking advantage of theopportunities for recycling, and minimize theFinal Use Zone. In this second option, the aimwould also be to reduce drainage flows to a levelwhere they are not in excess of environmentalcommitments. The selection of options wouldrequire detailed investigations of benefits andcosts.
Bhakra Irrigation System
The Bhakra irrigation system in India is locatedalong the divide between the Ganges and Induswater catchments. The Bhakra canal commandin Haryana state serves more than 1.2 millionhectares and contributes to about 40 percent ofHaryana’s wheat production and 6 percent of thenational production, and is thus very important toIndia’s national food security interests.
More than 98 percent of the command areais covered by alluvial plain lying between theSiwalik hills and Aravalli hills. Drainage isdifficult because of the saucer shapedtopography, and lack of surface and subsurfacedrains. Surface and subsurface drainage isabsent in this system. The system is describedin more detail in Sakthivadivel 1999;Bastiaanssen et al. 1999; Perry andNarayanamurthy 1998; Berkoff 1990; andMalhotra 1982. Groundwater is an importantsource of water, supplying irrigation water tomore than half of the command area, through
18
approximately 150,000 privately ownedtubewells. About 65 percent of the commandarea is underlain with marginal and salinegroundwater. Because groundwater qualityvaries with depth, these shallow tubewells tapmostly the upper unconfined aquifers, whilesome high capacity, deep augmentationtubewells were installed along Narwana, Bhakra,Ratia and Fatehbad canals to preventwaterlogging and supplement irrigation supplies.
The Bhakra canal irrigation system,introduced some 40 years ago, has changed thequality and use of groundwater in this area.Where groundwater quality is suitable forirrigation, there has been extensive groundwateruse, resulting in falling water tables over a largearea. In contrast, groundwater extraction hasbeen less than recharge in the brackish/salinebelt of the system. In these areas, the rate ofwater table rise has been noticed at 0.3–1.0 mper year.
Hydronomically, the entire Bhakra canalcontains a Regulated Recapture Zone andStagnation Zones pertaining to areas ofgroundwater extraction, and groundwater rise(figure 5).
• Regulated Rrecapture Zone withGroundwater Storage and Distributionand Negligible Pollution or SalinityLoading (RR with GWS and np/s). AtBhakra, much of the area comes under aRegulated Recapture Zone withgroundwater pumping. Groundwater isrecharged primarily by surface drainageflows from irrigation. Use of groundwaterwhere salinity is not a major concern iswidespread. The aquifer could also beused for water storage, but is nowconsidered primarily as a source of watersupply. In this zone, typically groundwatertables are declining at a high rate.
• Regulated Recapture Zone withGroundwater Storage and Distribution
and Pollution or Salinity Loading.(RR with GWS and p/s) TheRegulated Recapture Zone alsocontains areas where salinity is a majorconcern. There is a considerable area,especially in Sirsa and Hirsa servicecircles with deep saline groundwater atdepths greater than 20 m. In theseareas, surface water has to be usedcarefully in order to prevent build up ofsaline groundwater.
• Stagnation Zones (S). StagnationZones are those areas that are poorlydrained, and hence waterlogging andsalinity is a major problem. Watermanagement practices and technologiesin these areas that limit the buildup ofgroundwater assume great significancein sustaining the productivity of thissystem. If well managed, it is possibleto convert these Stagnation Zones intoRegulated Recapture Zones. On theother hand, it is also possible for theStagnation Zones to enlarge the threatto the sustainability of the region.
Water Management Strategies
Bhakra is basically a closed basin with allwater allocated to various uses (Molden et al.2000). There are opportunities and threatsdepending on the zone. Farmers are takingadvantage of the opportunity provided bygroundwater use resulting in productive andprofitable agriculture. Unfortunately, it will bedifficult to add substantially more supplies bywater savings, although aggressiveconservation measures can yield some water.The biggest opportunity lies in increasing theproductivity of water in terms of increasedagricultural output and increased economicbenefit for every unit of water consumed.
The biggest challenge at Bhakra, in ourview, is managing threats to sustainability. In
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the Regulated Recapture Zone with freshgroundwater, the biggest threat to sustainabilityis groundwater mining. Groundwater rechargeby heavy monsoon rains is an option.Institutional solutions to regulate groundwaterseem difficult to find, and difficult to implement.But an aggressive search for these solutions iswarranted.
In the Regulated Rrecapture Zone withsaline groundwater, the biggest concerns aremanaging salinity and preventing groundwaterbuild up. An important approach is to
minimize the mobilization of salts from deepaquifers, so as not to add more salts toreasonably good quality water. Water ofmarginal quality can be mixed with fresh waterfor irrigation, if it is economical.
There is a threat of growing areas ofstagnation. In the Stagnation Zone, an importantoption is the addition of drainage. A secondoption is to limit the amount of canal watercoming into this area, and improve the reliabilityof supply and farm management practices wheredeep percolation is limited.
FIGURE 5.
Bhakra Canal Command Area.
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Gediz Basin
The Gediz Basin in Western Turkey has a typicalMediterranean climate, hot, dry summers andcool winters (see IWMI and GDRS 2000 for adetailed description of the basin). The Gedizriver has a length of about 275 km, drains anarea of 17,700 km² and flows from east to westinto the Aegean Sea just north of Izmir. Meanannual precipitation in the basin ranges fromalmost 800 mm in the 2,300 m high mountains tobelow 500 mm near the Aegean coast.Temperatures range from –24 °C at highelevations in winter to over 40 °C in the interiorplains in summer. The natural vegetation of thebasin is mainly shrubland, maki (bay, myrtle,scrub oak and juniper trees, among others) andconiferous forest with large outcrops of barrenlimestone mountain.
The Gediz basin is an important agriculturalbasin, with irrigation as a main water use. Gedizriver water serves irrigation, municipal andindustrial uses. A wetland of about 15,000 ha liesat the tail end of the Gediz river. The basin canbe divided into four distinct zones: Water SourceZone (WS); a Natural Recapture Zone (NR), aRegulated Recapture Zone (RR); and anEnvironmentally Sensitive (E) Zone (figure 6).
• Water Source Zone (WS): The WaterSource Zone is situated upstream of theirrigated area in the Gediz basin. Ananalysis of the rainfall pattern in thebasin indicates that the portion of theGediz basin above the Demirköprüreservoir contributes most of the runoff tothe basin because it has higherprecipitation and lower evapotranspirationthan the rest of the basin. The annualrunoff cycle shows peaks in winter andspring, with flows decreasing over thesummer and fall periods. TheDemirköprü reservoir came into operationin the year 1970. Apart from the
Demirköprü reservoir, and two smallerreservoirs on the Alasehir river, themajor waterbody in the basin is GölMarmara, a natural lake which is alsofed by diversions from the Gediz andKum rivers and used to store winterflows for the summer irrigation period.
A comparison of the flow (maximum,minimum and mean) to the Demirköprüreservoir and flow at the outlet of Gedizbasin indicates that much of the flow tothe Gediz basin emanates upstream ofthe Demirköprü reservoir. There is verylittle contribution provided by thetributaries such as Alasehir (2,700 km²),Nif (1,100 km²) and Kum (3,200 km²)which are on the downstream side ofthe Demirköprü reservoir (IWMI andGDRS 2000).
• Natural Recapture Zone withGroundwater Distribution (NR withGWD). The whole of the Gediz valleysituated between Demirköprü reservoirand Emiralem regulator is a NaturalRecapture Zone interspersed with smallWater Source Zones consisting ofconiferous forest and maki cover.Agricultural land covers 62 percent ofthe valley, about half of which isirrigated. Irrigation water is divertedfrom the Demirköprü dam and GölMarmara, a natural lake in the floor ofthe valley. Three diversion weirs orregulators were constructed on theGediz downstream of Demirköprü andtwo additional dams built in the uppervalley near Alasehir. The topographyand drainage of the basin is such thatall water re-entering the hydrologiccycle is directed back into the Gedizriver, and water is reused at severallocations.
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FIGURE 6.
Gediz River Basin, Turkey.
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Groundwater is an important source ofwater, increasing in importance after thedrought of 1989–1994. Within the mainvalley there does not seem to be aproblem with falling or rising groundwaterfrom excess canal water. Many farmersuse both canal water and groundwater,although somewhere between 30-40percent of the total area appears to beirrigated solely by groundwater orpumping from drains and rivers.
• Natural Recapture Zone withGroundwater Distribution andPollution and Salinity Loading (NRwith GWD and p/s). The return flowsfrom municipalities and villages arecause for concern because some of thewater is polluted with human and otherwaste. The most rapidly urbanizing andindustrializing area is in the upper Nifvalley immediately east of Izmir. Manyfactories extract groundwater and thendischarge polluted water back into theGediz basin. The city of Manisa is alsoa rapidly expanding industrial areacausing a lot of pollution in the Gedizbasin. This condition of pollution loadingaffects uses within the area, anddownstream uses of water.
• Regulated Recapture Zone withGroundwater Distribution (RR withGWD): The Meneman delta (belowEmiralem regulator) is the closure areaof the Gediz basin. This delta is fertileland supporting an irrigated area ofroughly 23,000 ha. This is mostly cottonirrigated through right and left bank canaltakeoff from Emiralem regulator. Theupstream part of the delta is demarcatedas a Regulated Recapture Zone because
farmers use shallow groundwater, whichis recharged primarily by irrigation, toaugment supplies. The deepgroundwater is saline, and is not usedfor agriculture. Most farmers growingvegetables and fruits feel they can nolonger use canal water, and otherscomplain of skin diseases and otherproblems as a direct result of contactwith canal water. In this zone, drainagewater takes either one of two paths.Water either drains to downstreamwetlands or it re-enters the main riverchannel, where it is reused. There isvery little drainage outflow in this area;thus no final use zone has beendemarcated. Even the extreme tail-endfarmers mix drain, canal andgroundwater.
• Environmentally Sensitive (E) Zone:The Bird Paradise (14,900 ha) at the tailend of Gediz basin is one of ninewetlands in Turkey declared as a“Wetland of International Importance”under the convention of Ramsar by theTurkish Government, and is thusclassified as an EnvironmentallySensitive Zone. It is an importantbreeding or over-wintering area for manybird species such as flamingos, pelicans,herons and others. Protection of theBird Paradise has become difficult as itis located at the end of the Gediz riverand is therefore very sensitive tochanges of land use or climate. In 1992,the water shortage in the Gediz river ledto a drying up of significant areas of thewetland and the death of thousands ofbirds. Changes in upstream use in termsof quality and quantity affect thisEnvironmentally Sensitive Zone.
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Water Conservation Strategies
The Gediz basin is essentially closed, andthere is only limited scope for real watersavings. Most water savings opportunitieshave already been taken. The RegulatedRecapture Zone has already extended throughthe Menemen plains reducing drainageoutflows. Drip and sprinkler irrigationthroughout the basin may yield some watersavings by decreasing non-beneficialevaporation. These and other on-farmpractices can result in increasing theproductivity of water consumed by agriculture.
A constraint on improving the economicproductivity of water is the pollution emanatingfrom the pollution loading in a Natural RecaptureZone, which adversely affects downstream usersby limiting crop choice and causing a healthhazard. Basin management strategies need toaddress this issue to solve this major problem.
There are threats, besides pollution loading,that would decrease the overall productivity ofwater in the basin. Groundwater use hasincreased to levels that may not be sustainable,although this is not yet clear. Increased upstreamuse and degraded quality affect the downstreambird sanctuary.
Lessons from Case Studies
The layout of zones often follows a path asdepicted in figure 2. Water Source areas are inthe upstream, followed by a Natural RecaptureZone. Near the coast there is a RegulatedRecapture Zone, and lastly, a Final Use Zone.But this pattern is not always the case as seenin the Bhakra example. This subbasin consistsof Regulated Recapture Zones interspersed withStagnation Zones. With more applications,more patterns will be found.
The zones are not a fixed physical feature ofthe landscape. They are dependent both onlandscape characteristics, and on infrastructureand management practices. For example,provision of drainage can remove a StagnationZone. Thus, Stagnation Zones can grow orshrink. An interesting interplay is between theRegulated Recapture Zone and the Final UseZone. Kirindi Oya has a fairly wide Final UseZone relative to the total area. At the otherextreme, we did not identify a clear Final UseZone within Gediz. Farmers of Gediz practicesome sort of reuse, either by pumping drainagewater or groundwater, right up to the last pieceof irrigated land next to the sea. They follow a
sound conservation strategy of reducing the FinalUse Zone, and increasing the RegulatedRecapture Zone. This leads us to conclude thatthe interfaces between zones are not permanentbut vary with management approaches anddegree of scarcity. In the case of Gediz, theFinal Use Zone is completely eliminated and withstill further stresses, the Regulated RecaptureZone may even move upstream to impinge onthe Naturally Recaptured Zone.
Excepting Bhakra, opportunities for savingwater are most obvious in the downstream endof basin at the Closure Management Areaconsisting of the Regulated Recapture and FinalUse Zones. The strategy is to reduce drainageoutflows to an acceptable environmental limit.To do so requires a combination of reuse withinthe Regulated Recapture Zone, and highClassical Efficiency improvements in the FinalUse Zone. In other areas, saving strategies arefocused on reducing pollution loading, andreducing non-beneficial evaporation.
Hydronomic zones also lay out threats.Often times, the scope for water savings is smallas in the case of Egypt’s Nile, the Bhakra
24
subbasin, and the Gediz basin. In theseclosed and closing basins, management effortsshould be focused on these threats. Salt-loading at the lower end of the Nile and withinBhakra is a major threat. Groundwater
Discussion
Understanding the dynamics of water use in awater basin at first seems a formidable task.Superimposed on the natural hydrologic systemare human-made structures altering the courseof flow paths for our use. People, influenced byculture, politics, and other diverse incentives,operate these structures, resulting in flows ofwater that are often different from originalintentions. Over time population grows, and theneeds of people change, resulting in an everchanging set of water relationships within abasin. Over time we are continually adjustingand looking for ways to manage water better.Given all these complexities, how do weconceptualize, form, and describe options forimprovement within a basin?
Hydronomic zones and water accounting aremethodologies that try to simplify complexrelationships to help us understand the presentsituation of water use, the changes in how wateris being used, and to visualize how changes mayaffect the performance in basin-wide water use.They are first approximation tools to help usquickly obtain an initial grasp of basin behavior.They allow the identification of issues that mustbe further probed. They provide contextualinformation about the basin, within which we canfurther study the complexities of water use.
Conceptualizing basin water use with the aidof hydronomic zones holds promise for severalapplications. For many water-related activities, itis not necessary to completely understand the
dynamics and interactions within the entire basin.Conservation options and performanceconsiderations are related to the zone ratherthan the entire basin. This has the potential tosave considerable time and effort in basinanalysis.
As a first approximation tool, hydronomiczones have limitations. They do not provide theresolution needed for more detailed performanceassessment or design of solutions. They areonly meant to give an overview and to help ourinitial thinking. The divisions between zonesmay not be so sharp, or even if there are sharpdivision lines between zones, they may bedifficult to map out precisely. Thus, maps drawnwith zones should be used as rough guidelines,rather than precise zoning tools. With thedevelopment of basin water resources thelocations of interfaces between zones can alsoshift.
Detailed analyses are carried out many timesin one part of a basin and focus on one aspectof water resource use. For example, studies arecarried out to find out how to increaseapplication or irrigation system efficiency, or howto reduce demand for water by increased pricing.When promising solutions are found, the reactionis to apply these to all locations in a basin. Thisis often done without consideration of whethersolutions are appropriate to various parts of abasin, or how these solutions scale up to thebasin. For example, the most common error is
overdraft exists at Bhakra and possibly withinGediz. There is considerable pollution loadingin Egypt and the Gediz basin, posing a threat tothe productivity of agriculture and other wateruses.
25
to assume that improvements in applicationefficiency of water will save enormous quantitiesof water. Technologies to increase applicationefficiency combined with increased water pricing,and a demand management response, areindeed likely to reduce applications of water tofields and deliveries of water within an irrigationsystem. These changes come at a cost, and arenot necessarily easy to implement throughexisting institutions. Are they worth it? In FinalUse Zones, or where pollution is a concern inclosing and closed basins, there is likely to belarge gains in benefits when transferable watersavings are achieved, and more productive useof water is realized. In Regulated Recapture andNatural Recapture Zones, the result of demandmanagement interventions may simply be to alterthe course of water at an additional cost, withbenefits remaining constant. The role ofhydronomic zones would be to give an initialindication of where these demand managementinterventions are most appropriate, or to helpprioritize areas where interventions would lead tothe most benefits.
Hydronomic Zones can be useful in dealingwith the problem of spatial scales. We are oftenmost interested in working at one scale— forexample, an irrigated field, or a domestic watersupply system. Yet we hope that the actions wetake at this scale, when replicated, will havebroader consequence on basin water resources.When scaled-up, results are often not asanticipated because of reuse of drainage
outflows or solutions that apply in one part of thebasin are not appropriate for another part.Hydronomic Zones can at least help us to definesolutions that are applicable to similar areas.This is much like the concept of agro-ecosystems, where solutions are found forparticular agro-ecosystems so that they can bereplicated in other areas within the agro-ecosystem.
There are many other tools that help inexploring options for improved water use,including economic and hydrologic simulationand optimization models. There seems to besynergy between these approaches. Models arecapable of providing much more resolution andmore accuracy in predicting what may happenunder various scenarios. Various scenarios canbe conceptualized with the aid of hydronomiczones and then further tested through modeling.Alternatively, solutions given by modeling resultscan be checked for logic using the concepts ofhydronomic zones.
Hydronomic zones can play an importantrole in characterizing water basins. Whenmaking decisions that affect basin-wide wateruse, it is increasingly common to involvestakeholders in discussions. This zoning couldbe an effective tool in facilitating discussionsbetween people from various backgrounds. It isimportant to describe key differences in thehydrology and use of water within basins and itis important to know how potential changes mayaffect users.
26
Summary and Conclusions
A set of hydronomic zones are defined tocharacterize the combination of hydrologic andwater use settings within a basin. The zonesare based primarily on considerations of outflowof water from the particular areas. Genericstrategies for improving the productivity of wateruse were identified for each water managementzone. Water Source and EnvironmentallySensitive Zones were discussed in far lessdetail, and need to be addressed later throughresearch. They are kept here as referencepoints in that they need to be recognized andconsidered when developing basin managementstrategies.
Zoning was applied to four basins or majorparts of basins with diverse characteristics. Wewere able to somewhat rapidly sketch the zoneswithin the basins and draw some statementsabout considerations within each zone, andpossible water management strategies that mustbe considered by zone. These four casesprovide examples, and demonstrate that themethodology can cover a wide variety ofsituations.
There are several potential uses ofhydronomic zones:
• providing a quick overall characterizationof how water is used in a basin, andproviding an overview of specialconsiderations
• dividing a river basin into areas wherethere are distinctly different watermanagement considerations
• interpretation of water balanceperformance measures
• conceptualization of strategies to improvewater management
• isolation of areas with like problems, sothat the entire basin does not have to beconsidered in detail
• development of solutions for specifichydronomic zones, so that thesesolutions can be extended to likehydronomic zones in other areas
• providing information for use instakeholder discussions for people fromdiverse backgrounds
Zoning and classification are common anduseful practices in many fields, includingagriculture and water resources. We feel thatthis type of zoning is a novel, yet usefulapproach, to help in conceptualizing how wateris used in a basin, and to help in developingimproved water management practices. Overtime and with further examples, we expect thatthis method will evolve and find severalapplications.
27
Appendix
3. Canal seepage/leakage (decrease)a. Liningb. Maintenancec. Rotation instead of continuos flow
4. Operational spillage (decrease)a. Canal interceptor systemsb. Off-canal regulating reservoirsc. Better match between supply and demand
i. Improved schedulingii. Enhanced communicationsiii. Improved flow calibration and
managementiv. Canal automation
5. Deep percolation (decrease)a. Improved distribution uniformity
i. Precision levelingii. Shorter furrow or graded border
lengthsiii. Sprinkle or trickle irrigation on high
infiltration rate soilsb. Deficit irrigation
i. Reduced irrigation frequency(increase soil water depletionbetween irrigations)
ii. Reduced depth of irrigationc. Grow deeper rooted crops
6. Surface water runoff (decrease)a. Tailwater recovery systems for furrow
and graded border irrigationb. Shorten furrow or graded border lengthsc. Replace furrow and graded border
irrigation withi. Level basin irrigationii. Sprinkle irrigation
iii. Trickle irrigation
Conservation Measures to Increase Classical Efficiency or Process Fraction
In general the conservation measures that areaddressed in formulating a water managementplan are designed to increase the AvailableWater (AW), decrease non-beneficial evaporativedepletions or increase the local or MezzoEfficiencies: CE (Classical Efficiency) or PF(Process Fraction)6. In designing conservationmeasures through CE or PF, they can beorganized in relation to the flow paths implicit inthe terms of CE or PF applied within orthroughout each hydronomic zone. To increaseCE, either the numerator must be increasedproportionally more than the denominator isincreased or the denominator must be decreasedproportionally more than the numerator isdecreased.
The flow paths and means for decreasing (orincreasing) them to improve or increase CE areas follows:
1. Evaporation (decrease)a. Deficit irrigation
i. Reducing frequencyii. Reducing depth of irrigation
b. Drip irrigation (to reduce surface areawetted)
c. Sprinkle irrigate at night and/or duringlow wind periods
d. Mulching
2. Crop transpiration (decrease or increase)a. Planting at a different date when the
potential ET is lessb. Using a shorter season varietyc. Crop substitution with a crop having a
lower ETa
6The amount of water depleted by agricultural, industrial or municipal processes divided by rain and other inflows to the domain. For agricultureat field level. This is - ETa/(Rain + Div).
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29
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Molden, D. J.; R. Sakthivadivel; and Z. Habib. 2000. Accounting for use and productivity of water: Examples fromSouth Asia. IWMI Research Report 49. Colombo, Sri Lanka: International Water Management Institute.
Molden, D. J.; and R. Sakthivadivel. 1999. Water accounting to assess use and productivity of water. InternationalJournal of Water Resources Development 15(142): 55-71.
Molden, D. J.; M. El Kady; and Z. Zhu. 1998. Use and productivity of Egypt’s Nile. Paper presented at the 14th TechnicalConference on Irrigation, Drainage and Flood Control. Phoenix, Arizona, June 3-6, 1998. United States Committeeon Irrigation and Drainage.
Molden, D. J. 1997. Accounting for water use and productivity. SWIM Report 1. Colombo, Sri Lanka: InternationalIrrigation Management Institute.
Perry, C. J.; and S. G. Narayanamurthy. 1998. Farmer response to rationed and uncertain irrigation supplies. ResearchReport 24. Colombo, Sri Lanka: International Water Management Institute.
Renault, D.; M. Hemakumara; and D. J. Molden. 2000. Importance of water consumption by perennial vegetation inirrigated areas of the humid tropics: Evidence from Sri Lanka. Agricultural Water Management. 46(3):215-230.
Sakthivadivel, R.; S. Thiruvengadachari; U. Amerasinghe; W.G.M. Bastiaanssen; and D. J. Molden. 1999. Performanceevaluation of the Bhakra Irrigation System, India, using remote sensing and GIS techniques. IWMI Research Report28. Colombo, Sri Lanka: International Water Mangement Institute.
Seckler, D. W. 1996. The new era of water resources management: From “dry” to “wet” water savings. ResearchReport 1. Colombo, Sri Lanka: International Irrigation Management Institute.
van Eijk, A.; D. J. Molden; and R. Sakthivadivel. 1999. Water uses in the Kirindi Oya subbasin. In Multiple uses ofwater in irrigated areas: A case study from Sri Lanka, eds. M. Bakker; R. Barker; R. Meinzen-Dick; and F. Konradsen.SWIM Paper 8. Colombo, Sri Lanka: International Water Mangement Institute.
WRSR (Water Resources Strategic Research). 1996a. National level strategies and policies for utilizing Egypt’s Nilewater resources. Water Resources Strategic Research Activity Report 1. Cairo, Egypt: National Water ResearchCenter, Ministry of Public Works and Water Resources, Winrock International Institute for Agricultural Developmentand the US Agency for International Development.
WRSR. 1996b. Beheira pilot study area integrated water conservation and utilization program. Water ResourcesStrategic Research Activity Report 2. Cairo, Egypt: National Water Research Center, Ministry of Public Works andWater Resources, Winrock International Institute for Agricultural Development and the US Agency for InternationalDevelopment.
Research Reports
42. Comparison of Actual Evapotranspiration from Satellites, Hydrological Modelsand Field Data. Geoff Kite and Peter Droogers, 2000.
43. Integrated Basin Modeling. Geoff Kite and Peter Droogers, 2000.
44. Productivity and Performance of Irrigated Wheat Farms across Canal Commands inthe Lower Indus Basin. Intizar Hussain, Fuard Marikar, and Waqar Jehangir, 2000.
45. Pedaling out of Poverty: Social Impact of a Manual Irrigation Technology in SouthAsia. Tushaar Shah, M. Alam, M. Dinesh Kumar, R. K. Nagar, and Mahendra Singh,2000.
46. Using Remote Sensing Techniques to Evaluate Lining Efficacy of Watercourses.R. Sakthivadivel, Upali A. Amarasinghe, and S. Thiruvengadachari, 2000.
47. Alternate Wet Dry Irrigation in Rice Cultivation: Saving Water and Controlling Malariaand Japanese Encephalitis? Wim van der Hoek, R. Sakthivadivel, Melanie Renshaw,John B. Silver, Martin H. Birley, and Flemming Konradsen, 2000.
48. Predicting Water Availability in Irrigation Tank Cascade Systems: The CASCADEWater Balance Model. C. J. Jayatilaka, R. Sakthivadivel, Y. Shinogi, I. W. Makin, andP. Witharana, 2000.
49. Basin-Level Use and Productivity of Water: Examples from South Asia. David Molden,R. Sakthivadivel, and Zaigham Habib, 2000.
50. Modeling Scenarios for Water Allocation in the Gediz Basin, Turkey. Geoff Kite, PeterDroogers, Hammond Murray-Rust, and Koos de Voogt, 2001.
51. Valuing Water in Irrigated Agriculture and Reservoir Fisheries: A Multiple Use IrrigationSystem in Sri Lanka. Mary E. Renwick, 2001.
52. Charging for Irrigation Water: The Issues and Options, with a Cast Study from Iran. C.J. Perry, 2001.
53. Estimating Productivity of Water at Different Spatial Scales Using Simulation Modeling.Peter Droogers, and Geoff Kite, 2001.
54. Wells and Welfare in the Ganga Basin: Public Policy and Private Initiative in EasternUttar Pradesh, India. Tushaar Shah, 2001.
55.Water Scarcity and Managing Seasonal Water Crisis: Lessons from the Kirindi OyaProject in Sri Lanka. R. Sakthivadivel, Ronald Loeve, Upali A. Amarasinghe,and Manju Hemakumara, 2001.
56. Hydronomic Zones for Developing Basin Water Conservation Strategies. David J.Molden, Jack Keller, and R. Sakthivadivel. 2001.
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