26324 Water Resources and Environment Technical Note F.2 Water Conservation: Irrigation Series Editors Richard Davis Rafik Hirji WATER RESOURCES AND ENVIRONMENT TECHNICAL NOTE F.2 Water Conservation: Irrigation SERIES EDITORS RICHARD DAVIS, RAFIK HIRJI The World Bank Washington, D.C. Water Resources and Environment Technical Notes A. Environmental Issues and Lessons Note A.1 Environmental Aspects of Water Resources Management Note A.2 Water Resources Management Policy Implementation: Early Lessons B. Institutional and Regulatory Issues Note B.1 Strategic Environmental Assessment: A Watershed Approach Note B.2 Water Resources Management: Regulatory Dimensions Note B.3 Regulations for Private Sector Utilities C. Environmental Flow Assessment Note C.1 Environmental Flows: Concepts and Methods Note C.2 Environmental Flows: Case Studies Note C.3 Environmental Flows: Flood Flows Note C.4 Environmental Flows: Social Issues D. Water Quality Management Note D.1 Water Quality: Assessment and Protection Note D.2 Water Quality: Wastewater Treatment Note D.3 Water Quality: Nonpoint-Source Pollution E. Irrigation and Drainage Note E.1 Irrigation and Drainage: Development Note E.2 Irrigation and Drainage: Rehabilitation F. Water Conservation and Demand Management Note F.1 Water Conservation: Urban Utilities Note F.2 Water Conservation: Irrigation Note F.3 Wastewater Reuse G. Waterbody Management Note G.1 Groundwater Management Note G.2 Lake Management Note G.3 Wetlands Management Note G.4 Management of Aquatic Plants H. Selected topics Note H.1 Interbasin Transfers Note H.2 Desalination Note H.3 Climate Variability and Climate Change Copyright © 2003 The International Bank for Reconstruction and Development/THE WORLD BANK 1818 H Street, N.W., Washington, D.C. 20433, U.S.A. All rights reserved. Manufactured in the United States of America First printing March 2003 2 CONTENTS Foreword 5 Acknowledgments 7 Introduction 9 Concepts of Water Conservation in Irrigation 11 Because of the interdependencies between sectors, water conservation in irrigation needs to be planned in an integrated and comprehensive manner with Authors other basin users and stakeholders, using a good Hervé Plusquellec and understanding of the local surface and groundwa- Walter Ochs ter resources and their relation to the environment Technical Adviser Stephen Lintner Physical Water Conservation Techniques 16 To provide efficient use of water resources, conserva- Editor tion techniques should be applied at all stages of the Robert Livernash irrigation system from the storage reservoir to field application. Two of the most important ways to increase Production Staff the efficiency of water diverted for irrigation are by Cover Design: Cathe Fadel introducing reforms in the operation of irrigation dis- tricts and by use of good agronomic techniques, in- Design and Production: cluding water conserving crop varieties. The Word Express, Inc. Notes Institutional and Policy Reforms 23 Unless otherwise stated, Technical changes need to be associated with institu- all dollars = U.S. dollars. tional and policy reforms to improve the efficiency and All tons are metric tons. productivity of irrigation projects. Conclusion 28 Cover photo by Hervé Plusquellec, World Bank Low Energy Precise Application Further Information 28 center pivot irrigator This series also is available on the World Bank website (www.worldbank.org). 3 WATER RESOURCESANDENVIRONMENT · TECHNICAL NOTE F.2 Boxes 1. Definitions of irrigation efficiency 11 2. The use of remote sensing for planning and managing water allocations 16 3. Factors affecting seepage from unlined canals 18 4. Field research study on brick canal lining performance in Punjab, India 18 5. Canal lining programs in the Tarim Basin, Xinjiang province, China 19 6. Surface irrigation methods 21 7. Desirable elements in a national water irrigation conservation program 24 8. Office du Niger, Mali: From failure to success 25 9. Volumetric water measurement in Morocco 26 10. Social and business user associations 27 Figures 1. Typical water balance of irrigation projects 12 2. Cross-section of supply channel designed to provide water to 15 turn-outs only at full supply level. Tables 1. Typical irrigation efficiencies 13 2. Water balance and efficiencies of the Indus Basin Irrigation System 13 3. Approximate application efficiency of various on-farm irrigation 20 systems and methods 4. Comparative costs of piped irrigation systems 21 4 WATER CONSERVATION: IRRIGATION FOREWORD The environmentally sustainable development and priority in Bank lending. Many lessons have been management of water resources is a critical and learned, and these have contributed to changing complex issue for both rich and poor countries. It attitudes and practices in World Bank operations. is technically challenging and often entails difficult trade-offs among social, economic, and political con- Water resources management is also a critical de- siderations. Typically, the environment is treated velopment issue because of its many links to pov- as a marginal issue when it is actually key to sus- erty reduction, including health, agricultural tainable water management. productivity, industrial and energy development, and sustainable growth in downstream communi- According to the World Bank's recently approved ties. But strategies to reduce poverty should not lead Water Resources Sector Strategy, "the environment to further degradation of water resources or eco- is a special `water-using sector' in that most envi- logical services. Finding a balance between these ronmental concerns are a central part of overall objectives is an important aspect of the Bank's in- water resources management, and not just a part terest in sustainable development. The 2001 Envi- of a distinct water-using sector" (World Bank 2003: ronment Strategy underscores the linkages among 28). Being integral to overall water resources man- water resources management, environmental agement, the environment is "voiceless" when other sustainability, and poverty, and shows how the 2003 water using sectors have distinct voices. As a con- Water Resources Sector Strategy's call for using sequence, representatives of these other water us- water as a vehicle for increasing growth and re- ing sectors need to be fully aware of the importance ducing poverty can be carried out in a socially and of environmental aspects of water resources man- environmentally responsible manner. agement for the development of their sectoral in- terests. Over the past few decades, many nations have been subjected to the ravages of either droughts or floods. For us in the World Bank, water resources man- Unsustainable land and water use practices have agement--including the development of surface and contributed to the degradation of the water resources groundwater resources for urban, rural, agriculture, base and are undermining the primary investments energy, mining, and industrial uses, as well as the in water supply, energy and irrigation infrastruc- protection of surface and groundwater sources, pol- ture, often also contributing to loss of biodiversity. lution control, watershed management, control of In response, new policy and institutional reforms water weeds, and restoration of degraded ecosys- are being developed to ensure responsible and sus- tems such as lakes and wetlands--is an important tainable practices are put in place, and new predic- element of our lending, supporting one of the es- tive and forecasting techniques are being developed sential building blocks for sustaining livelihoods and that can help to reduce the impacts and manage for social and economic development in general. the consequences of such events. The Environment Prior to 1993, environmental considerations of such and Water Resources Sector Strategies make it clear investments were addressed reactively and prima- that water must be treated as a resource that spans rily through the Bank's safeguard policies. The 1993 multiple uses in a river basin, particularly to main- Water Resources Management Policy Paper broad- tain sufficient flows of sufficient quality at the ap- ened the development focus to include the protec- propriate times to offset upstream abstraction and tion and management of water resources in an pollution and sustain the downstream social, eco- environmentally sustainable, socially acceptable, logical, and hydrological functions of watersheds and economically efficient manner as an emerging and wetlands. 5 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 With the support of the Government of the Nether- The Notes are in eight categories: environmental lands, the Environment Department has prepared issues and lessons; institutional and regulatory is- an initial series of Water Resources and Environ- sues; environmental flow assessment; water qual- ment Technical Notes to improve the knowledge ity management; irrigation and drainage; water base about applying environmental management conservation (demand management); waterbody principles to water resources management. The management; and selected topics. The series may Technical Note series supports the implementation be expanded in the future to include other relevant of the World Bank 1993 Water Resources Manage- categories or topics. Not all topics will be of inter- ment Policy, 2001 Environment Strategy, and 2003 est to all specialists. Some will find the review of Water Resources Sector Strategy, as well as the past environmental practices in the water sector implementation of the Bank's safeguard policies. useful for learning and improving their perfor- The Notes are also consistent with the Millennium mance; others may find their suggestions for fur- Development Goal objectives related to environmen- ther, more detailed information to be valuable; while tal sustainability of water resources. still others will find them useful as a reference on emerging topics such as environmental flow assess- The Notes are intended for use by those without ment, environmental regulations for private water specific training in water resources management utilities, inter-basin water transfers, and climate such as technical specialists, policymakers and variability and climate change. The latter topics are managers working on water sector related invest- likely to be of increasing importance as the World ments within the Bank; practitioners from bilateral, Bank implements its environment and water re- multilateral, and nongovernmental organizations; sources sector strategies and supports the next gen- and public and private sector specialists interested eration of water resources and environmental policy in environmentally sustainable water resources and institutional reforms. management. These people may have been trained as environmental, municipal, water resources, ir- rigation, power, or mining engineers; or as econo- mists, lawyers, sociologists, natural resources Kristalina Georgieva specialists, urban planners, environmental planners, Director or ecologists. Environment Department 6 WATER CONSERVATION: IRRIGATION ACKNOWLEDGMENTS The Bank is deeply grateful to the Government of Technical Note F.2 was drafted by Hervé Plusquellec the Netherlands for financing the production of this and Walter Ochs, building on the earlier work done Technical Note. by Jan Hoevenaars and Roel Slootweg of Geoplan of the Netherlands. It was reviewed by Doug Olson and Safwat Abdel-Dayem of the World Bank. 7 WATER CONSERVATION: IRRIGATION INTRODUCTION As demand for water continues to rise rapidly and This Technical Note is one of three dealing with new sources of supply become scarcer, the conser- irrigation and drainage (I&D) issues. Technical vation of water is increasingly important. Compe- Notes E.1 and E.2 focus on environmental aspects tition among water users affects irrigated agriculture of irrigation and drainage development and reha- in many arid and semiarid areas. These pressures bilitation. This Note focuses on water conservation will become more severe as water supplies are more in irrigation. It starts with considerations of effi- fully utilized. Globally, agriculture accounts for 70 ciency and the importance of taking an integrated percent of water consumption, while industry ac- approach to water conservation in irrigation. The counts for 23 percent and households for 8 percent.1 second section of this note presents techniques to In developing countries, agriculture accounts for reduce losses from the conveyance and distribution an even higher share of 80 percent. Consequently, systems, the different methods for on-farm water even small improvements in irrigation water-use savings, and finally methods for improving opera- efficiency can make significant quantities of water tional flexibility and reliability--a prerequisite to available to further irrigation or to other users. improved water use at farm level. The last section discusses the policy tools that can be used to en- The World Bank's recently published Rural Strat- courage irrigators to use water more efficiently. egy states that future investment priorities for agri- cultural water use will focus on improving the A major conclusion of this Note is that neither tech- productivity of existing systems. This will not only nology nor policy reforms alone are sufficient to defer the need for investment in new sources of bring about more efficient use of irrigation water. water, but will also potentially protect natural re- More efficient application techniques will not be sources and the environment by making water avail- adopted by the water users if they are not accom- able for natural stream flows. The Strategy also panied by changes in pricing and improved opera- points out that irrigation and drainage development tion of the water supply system. and improvements will need to be planned and executed as part of integrated watershed/catchment 1"Water Resources 2000-2001. People and Ecosystem: The systems. Fraying Web of Life". UNDP, UNEP, World Bank, Water Resources Institute, Washington D.C. Bank orld ,W Ochs alter W by Photo Irrigation canal, Inner Mongolia, China 9 WATER CONSERVATION: IRRIGATION CONCEPTS OF WATER CONSERVATION IN IRRIGATION WATER CONSERVATION AND It is normal practice in irrigation engineering to EFFICIENCY assess the efficiency of irrigation systems at differ- ent levels: main canal, secondary and branch ca- nals, tertiary system, and farm level. The efficiencies Water conservation in irrigation is an important of these different levels are the percentages of the component of efforts to use water efficiently. Increas- volumes of water supplied to the next level down ing competition for water resources in many river compared to the volumes diverted from the higher basins of the world dictates the need for careful plan- levels. These efficiencies measure seepage and spill- ning and priority setting. The multiple uses of wa- age losses and reflect an engineering perspective. ter make stakeholder participation in planning and While efficiency within an irrigation system need management of water use systems, such as irriga- only consider irrigation water use, basin-wide effi- tion, a critical component of water conservation ciency must take account of all beneficial water uses. programs. Box 1 defines water use efficiencies at different stages of an irrigation system and its source. Movement of water through an irrigation system, from the water source (river, lake, reservoir) to the However, efficiency alone is not enough to define crop, can be considered as three stages: the performance of an irrigation project. Quality of Conveyance. The movement of water from its service and indicators of productivity also need to source through the main and secondary canals be considered. For example, a canal system could or conduits to the tertiary off-takes. have very high conveyance efficiency with a mini- Distribution. The movement of water through mum of seepage and spillage losses, but if delivery the tertiary and on-farm canals or conduits to of water is rigid or unreliable, there will be consid- the field inlet. erable waste further down at the farm level. Flex- Field application. The movement of water from ible and reliable service is the best user incentive the field system and the application system to for water conservation, because it gives security to the crop. the user. The productivity of water is often defined as the value of marketable produce per unit of wa- Water conservation should be addressed in all three ter. Indicators of the quality of irrigation service, stages. and indicators of productivity along with efficien- BOX 1. DEFINITIONS OF IRRIGATION EFFICIENCY Basin water use efficiency (E ). The percent of the catchment yield applied to beneficial uses in the catchment and its b near-shore areas. These uses include both production and environmental uses but exclude water lost to evaporation, unrecoverable groundwater, polluted water, and offshore flows to the ocean. Conveyance efficiency (E ). The volume of water delivered to the distribution system divided by the volume of water c diverted from the water sources. Distribution efficiency (E ). The volume of water delivered to the fields divided by the volume of water delivered to the d distribution system. Field efficiency or water application efficiency (E ). The net irrigation water requirements minus effective rainfall (IWR) f (sometimes defined as the volume of water required that will not create undesirable stresses in crops) divided by the volume of water delivered to the fields. Overall irrigation efficiency (E ). The net irrigation water requirements minus effective rainfall (IWR) divided by the o volume of water diverted from water sources. 11 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 cies are needed to evaluate performance of irriga- When planning water conservation measures, re- tion projects. alistic values should be used for conveyance, dis- tribution, and water application efficiencies rather These definitions of efficiency in irrigation systems than the optimistic values often found in textbooks. differ from efficiency in urban water systems. In Where possible, these values should be measured urban water systems, efficiency measures the vol- within the project area under current and realistic ume of water treated to the volume billed (or de- irrigation practices. Table 1 shows typical, measured livered) to the consumers. Unlike overall irrigation irrigation efficiencies achieved in Bank-financed efficiency, which includes end (field) uses of the projects. water, urban water efficiency does not consider household use of water, which typically includes INTEGRATED WATER RESOURCES many wasteful practices. For comparative purposes, DEVELOPMENT it would be more relevant to compare irrigation conveyance and distribution efficiencies with ur- An important but little appreciated fact about irri- ban water efficiencies. However, conveyance and gation water use is that a substantial volume of water distribution efficiency is not able to be calculated is recycled, thus providing a significant benefit to accurately in most irrigation projects because of both other consumptive users and to the environ- the difficulties in measuring water volumes in ca- ment (Figure 1). Thus, part of the water diverted nal irrigation systems. for irrigation flows back into a stream or ground- FIGURE 1. TYPICAL WATER BALANCE OF IRRIGATION PROJECTS Inflow Evaporation Loss to Groundwater Reservoir Irrigation Canal Canal Seepage losses Diversion to Field Percolation losses Evapotranspiration Field Surface Drainage Rainfall rev Shallow Ri Crop Water Use Groundwater Beneficial Aquifer Environmental Uses Non-beneficial Pumped and Capillary Groundwater Evapotranspiration Return flow to river Deep drainage Sea 12 WATER CONSERVATION: IRRIGATION TABLE 1. TYPICAL IRRIGATION EFFICIENCIES Efficiencies (%) System Type E x E E E c d f o Open canal systems under manual control and surface application 60 50 30 Open canal systems under automatic control and surface application 70 60 42 Open canal system with advanced automatic control & field water-saving techniques 75 70 53 Pipe conveyance systems and drip techniques 95 75 71 water system, where it can be reused if the water Because water in a river basin can be used mul- quality has not deteriorated beyond acceptable lim- tiple times, the application of water conservation its. The remainder ­evaporation and transpiration, measures in irrigation can have both negative and drainage to the sea or a similar area, water that is positive impacts on third parties. A very effective too contaminated with salt, nutrients, pesticides to water conservation program in an irrigation scheme be useable - cannot be captured and reused and so could impair downstream users relying on ground- is lost to uses within the river basin. water recharge or on drainage water. Similarly, if the water allocated to an irrigation scheme remains Some of this reuse occurs within the irrigation sys- unchanged after conservation measures are imple- tem. The Indus River basin provides an example of recharge of the alluvial aquifers and reuse, provid- ing water with much higher value to most Paki- TABLE 2. stani irrigators. Tubewells were installed in large A) WATER BALANCE AND areas of the basin because surface water supplies B EFFICIENCIES OF THE ) INDUS BASIN IRRIGATION SYSTEM were not adequate for the desired extent of irriga- tion. The overall basin efficiency is estimated at A) Phase of Quantity water cycle (Million acre-feet) about 64 percent, about 60 percent higher than the combined efficiency of the surface system at about Total river inflow 160 40 percent (Table 2). The field efficiency is very high because of under-irrigation and the amount of wa- Canal diversion 107 ter recycled through the tubewells. Recharge of groundwater 56.4 Saline 19.7 Much of the water lost to transpiration comes from crops; a further amount comes from desirable Fresh 36.7 aquatic plants (wetlands, etc). However, not all tran- Crop use 68.2 spiration losses are beneficial. Some come from undesirable weed species and so are non-benefi- Flow to Arabian Sea 39 cial. Other losses come from fallow, waterlogged B) Efficiency % and salinized lands through capillary action, and evaporation. These evaporation losses are also non- Basin water use efficiency 64 beneficial. The problem of non-beneficial evapora- Conveyance efficiency 82 tion losses is exacerbated if shallow groundwater Watercourse efficiency 65 tables are created by irrigation inefficiencies. Field efficiency 75 13 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 mented in an area where there is inadequate allo- Because of these interdependencies, water conser- cation for ecosystems, there is likely to be an ex- vation in irrigation needs to be planned as part of a pansion or intensification of irrigation with no river basin plan involving other basin users and resulting environmental benefits. For example, the stakeholders. Water needs to be allocated to each imposition of a cap on water extractions in the of the uses in the basin based on the socioeconomic Murray-Darling Basin in Australia (see Note C.2) goals of the region and the country. Given that the is likely to lead to improved water use efficiency, major pathway by which water leaves the basin is reduced groundwater rrecharge, and reduced re- through evapotranspiration (ET) from cropland, turn flows to the rivers, making it difficult to meet rangelands, forests, natural areas (wetlands, etc) and instream flows for environmental purposes. Thus, non-beneficial land uses, it is sensible to allocate water conservation needs to be accompanied by water to these land uses in terms of ET. The alloca- controls on beneficial water consumption if these tions should include the flow requirements to main- perverse effects are to be avoided. This is discussed tain the aquatic environment and the services that below. it provides to communities of the river basin (Notes C.1-C.3). However, these points do not constitute a case against improving irrigation systems. Improving Given the complexity of pathways and opportuni- water application can substantially reduce the en- ties for reuse (Fig 1), it is very difficult to deliber- vironmental and production costs of salinization. ately manage the internal flow pathways, including The control of soil salinization requires that excess the various leakages. In simple terms, water for ir- salt be moved from the crop root zone, but this re- rigation is extracted from either surface or ground- quires only a minimal amount of water beyond the water sources; part is consumed through ET, and crop needs. The conservation of water is environ- the remainder is returned to surface or groundwa- mentally sound, and is the least expensive way to ter bodies and is available for other users. The only minimize drainage problems in irrigation project water that leaves the local hydrologic system is the areas. Inefficiencies at irrigation scheme level im- ET (the ET can return as precipitation, but this will pose costs on production, such as increased pump- almost always occur in areas geographically differ- ing cost in projects that depend on lift from a river, ent from the irrigation area and local basin) or and depressed crop yields, particularly in the tail- riverflows to the ocean. ends of irrigation projects. Efficiency improvements also produce other ben- efits, including improve- ments in human health, reductions in the cost of treating drinking water, less environmental con- tamination by agricultu- ral chemicals, and Bank reductions in the eco- orld nomic cost of multiple ,W water withdrawals.1 Plusquellec vé Her by Photo 1Gleick, P. 2000. Canal lining with geomembranes, Tarim Basin, China 14 WATER CONSERVATION: IRRIGATION Since the major loss to the hydrologic system is via HOW DESIGN AFFECTS PERFORMANCE ET, irrigation water conservation needs to be in OF IRRIGATION SYSTEMS terms of reductions in ET. For planning and man- agement purposes, it is convenient to divide ET into Many failures and problems in irrigation and drain- three categories: crop consumptive use (CU), envi- age are caused by designs that are outmoded or that ronmentally beneficial ET, and non-beneficial ET. paid insufficient attention to operational aspects. Water conservation planning in irrigation districts should be directed toward coming up with ways to The design standards adopted in many developed reduce non-beneficial ET and to maximizing crop and developing countries since the 1950s to de- yields and the value of crop production per unit of liver water according to crop demand were con- CU, while preserving environmentally beneficial ET. ceptually advanced. However, most of them failed This approach to managing by the end use of water to meet their objectives because of deficiencies in and not the internal flow pathways assumes that the water control technology and the complexity leakages and other internal losses will eventually of the operational procedures. Managing an irri- be used for one of these beneficial or non-benefi- gation system equipped with manually operated cial uses, and so shifts the focus away from manag- gates at each branching point is a very complex ing leakages and internal losses and toward task. The use of water control technology with managing only those leakages and losses that con- structures requiring frequent adjustments, which tribute to non-beneficial uses of the water. has often been the norm during the intensive de- velopment of irrigation in developing countries In practice, CU, beneficial ET, and non-beneficial from the 1960s to 1990s, has influenced the per- ET need to be measured and monitored to put this formance of irrigated agriculture. Additionally, new approach into practice. Until recently, this has many systems were designed to operate at full ca- been difficult and expensive. However, the continu- pacity without consideration for operation at less ing development of remote sensing technologies has than full supply (see Figure 2). The frequent fluc- made ET measurements both accurate enough and tuations in water level and flows due to changes economically acceptable for practical application in demand and supply accentuate the difficulty of at a regional scale. Remote sensing has also been delivering water to tail-end users. used to monitor ET usage at farm scale, although the accuracy is lower and the cost is greater than at a regional scale. Remote sensing of ET has the additional advantages that it can be used to show FIGURE 2. the time sequence of ET over months, seasons and CROSS SECTION OF SUPPLY CHANNEL DESIGNED TO PROVIDE years, and it allows for performance comparisons WATER TO TURNOUTS ONLY AT FULL SUPPLY LEVEL across different irrigation areas that are indepen- dent of local measurement techniques and stan- Control Turnout dards. Box 2 describes the growing experience in structure the application of remote sensing to irrigation man- Full supply (design discharge) agement. Water level at less than full supply Turnout Turnout Water level without control structure 15 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 BOX 2. THE USE OF REMOTE SENSING FOR PLANNING AND MANAGING WATER ALLOCATIONS Direct in situ measurement of evapotranspiration (ET) from crops is difficult because field measurement devices are expensive and require considerable knowledge to operate, and each type of plant exhibits a different response to atmospheric conditions. The heterogeneity of plants across an irrigation area makes the estimation of regional ET from point measurements subject to considerable error. These difficulties can be avoided if ET is calculated from remotely sensed satellite data. Although satellite-based remotely sensed data have been available since the 1970s, reliable algorithms to estimate ET from these data have only been developed since the mid-1990s. These algorithms have been usually applied at regional scale because the data from weather satellites (typically NOAA-AVHRR with 1 or 2 km2 pixels) are available daily and can be acquired free of charge on the Internet. Higher resolution data from LANDSAT and other such satellites with around 30x30 m pixels are needed for field-scale ET. They need to be purchased, are available less frequently, and only after a delay of some days. The accuracy of ET estimates from remote sensing is about 85 to 90 percent at field scale, comparable to estimates from traditional techniques. However, the accuracy at regional scale is better than 90 percent, and so remote sensing of ET is more accurate at this scale than with traditional methods. The SEBAL algorithm for estimating regional ET, developed by IWMI and ITC, Netherlands, has now been successfully trialed in a number of countries, including the United States, Turkey, Brazil, and China. For example, the technique was tested in a 79,000 ha pilot area within Awati county in the Tarim Basin, China using both NOAA-AVHRR and Landsat data. Both cereals and cotton are grown in the area. Estimates of water use were made for beneficial and non- beneficial uses at the scale of Water User Associations (typically 2000 ha each). The crops were consuming only 40 percent of the water delivered. The actual water distribution was calculated to be 47 percent for crops, 24 percent beneficial eco-system use and 2 percent non-beneficial evaporation. Some of the excess was also believed to be contributing to a rising water table. The maps of ET showed that the water productivity (kg of crop/m3 of water) of the 19 Water User Association areas was relatively low and, with one exception, did not vary significantly between WUAs. The maps also showed where the non-productive ET losses were occurring, thus helping direct managers to areas needing attention. Sources: W. Bastiaanssen and M.G. Bos (1999). Irrigation performance indicators based on remotely sensed data: A review of literature. Irrigation and Drainage Systems 13: 291-311; W. Bastiaanssen, (no date). Remote Sensing Monitoring in the Awati pilot area. WaterWatch, Wageningen, The Netherlands. Even donor-financed irrigation rehabilitation tion system to deliver water in a reliable and flex- projects have not always incorporated design prin- ible way. It is only when the main distribution sys- ciples that reflect an operational understanding of tem is well operated that farmers will invest in the whole system. Many have focused on improv- on-farm water saving techniques. Only then can ing irrigation efficiency at the farm level (field effi- high returns be obtained from an increased appli- ciency) where the over-use of water is the most cation of other complementary inputs and a better apparent. However, the inefficiency at farm level choice of crops. often reflects the inability of the main and distribu- PHYSICAL WATER CONSERVATION TECHNIQUES To provide efficient use of water sources, conser- agronomic changes and improvements in the op- vation techniques should be applied at all stages of eration of irrigation water delivery are more effec- the irrigation system from the storage reservoir to tive at conserving water than are improvements in field application. To be fully effective, these physi- irrigation technology such as canal lining and sprin- cal interventions need to be coupled with institu- kler systems. Changes in technology are often not tional and policy reforms. Experience shows that sustainable without considerable support activities 16 WATER CONSERVATION: IRRIGATION and, even when they are introduced successfully, rehabilitation and modernization of irrigation they can result in a reduction in leakage that was projects. There are many technical reasons for lin- being used for other beneficial uses without a no- ing irrigation canals: ticeable reduction in ET per unit crop produced. Reduction of water lost by seepage Increase in canal discharge capacity RESERVOIRS Limitation of weed growth Reduction of waterlogging Evaporation losses from reservoirs are several times Prevention of bank erosion smaller than downstream losses from seepage or More equitable water distribution and reduc- runoff, unless the reservoirs are very shallow, as tion in transmission time occurs with the numerous tanks in India. Attempts Prevention of damages to adjacent land to reduce evaporation from large reservoirs by Reduction of drainage cost spreading chemicals or physical barriers to evapo- Reduction of canal dimensions ration have not been successful. Reduction in right-of-way and land acquisition cost.2 For safety reasons, seepage losses through dam foundations are minimized during construction. Box 3 describes the factors affecting seepage from Seepage control is seldom considered in other parts unlined canals. of irrigation supply reservoirs. Modern lining tech- niques, using geomembranes, are frequently used Rigid lining (cast-in-situ concrete, pre-cast concrete in small- to medium-sized urban supply reservoirs panels and bricks) is still the most common tech- because of the higher return on investment and the nique of canal lining in developing countries. How- better topographic configuration of urban supply ever, rigid linings are often ineffective because of reservoirs compared to shallow, medium, and small poor construction, particularly the compaction of irrigation dams. Increasingly, geomembranes are the sub-base and the placing of concrete, and inad- being used to line small regulating reservoirs and equate operation of canals with drawdowns that are private ponds in irrigation projects in arid and semi- too rapid and frequent dewatering. Even lining that arid regions. has a good appearance may not be an effective seep- age barrier because of small cracks or deficient CANAL LINING joints that considerably reduce the effectiveness of the lining. Also, saturation of the soils after com- Water losses in unlined canals are usually high. One missioning of a canal can cause some settlement of of the most important ways to increase the efficiency the soil mass, resulting in wide gaps underneath of water diverted for irrigation is to reduce the the rigid slabs resulting in further cracks. Preven- amount of water lost by seepage during conveyance tive maintenance, including sealing of cracks and to farmers' fields. Total seepage losses from main repairs of joints, is vital for the long-term effective- and secondary canals range from 20 to 45 percent. ness of rigid canal linings. For example, the total losses in the Bari Doab canal in Pakistan were estimated at 47 cent of the inflow. 2An additional advantage of canal lining--reduction of The average loss of the 400-km Karakum canal in canal maintenance costs--is subject to debate. One of the Turkmenistan, which runs in mostly sandy soils, largest recurring maintenance costs in many canal sys- was estimated at 43 percent during the first year of tems is the removal of weeds and plants from unlined canal sections. High quality, hard surface linings, which operation, although it decreased in subsequent years are relatively impenetrable by weeds and plants, greatly as the water table rose. reduce the cost of weed control and removal from the canals. However, high maintenance and repair costs of Lining of canals is the most common component of some linings a few years after completion could offset packages proposed by irrigation agencies for the the savings on weed control 17 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 BOX 3. FACTORS AFFECTING SEEPAGE FROM UNLINED CANALS The main factors affecting seepage are: Characteristics of the soil profiles: seepage rates from unlined channels can range from about 0.05 m/day for clay soils to 0.5 m/day for sandy soils Geometry of canals: greater depth of water and greater wetted perimeter increase seepage rates Depth to groundwater Amount of sediment in the water Suspended material in the canal water is carried out by seepage into the pores in the soil. This is known as the self- sealing effect. For example, seepage losses immediately after construction of Donzere-Montdragon canal in France amounted to 16 m3/s; but were reduced to 3 m3/s within five years by the natural sealing effect of the silt-laden Rhone water. Canal lining is very expensive, adding 30 to 40 per- beneficial and non-beneficial uses and a realistic cent to the total cost of an unlined system. Invari- estimate of the water that can reasonably be saved ably the high investment cost is justified by the value by lining if the contribution to non-beneficial uses of water saved by reduction of seepage losses. This needs to be reduced. The contributions of seepage justification is usually based on research studies to beneficial uses can often outweigh any advan- that show that roughly 60 to 80 percent of the wa- tages from canal lining. ter lost in unlined canals can be saved by hard-sur- face lining. For example, research in Nebraska in Another option is to use flexible geomembraness 1986 showed that the seepage rates were reduced protected with a rigid lining or with loose materi- from about 300 to 140 mm/day and research in In- als. This technique was used first by the U.S. Bu- dia showed that seepage reductions after lining reau of Reclamation and in some Middle East ranged from 30 percent for main canals to 45 per- Countries with very difficult soils, including gyp- cent for distributary canals. Reduction of seepage sum soils (Esfahan project in Iran; Balikh project losses is often assumed to be constant for the ex- in Syria) in the 1970s. The Forwah-Sadiaqia project pected life of the lining. However, field experience in Pakistan's Indus Basin and the Tarim II Project and recent research studies do not always validate in Western China (Box 5) are two Bank-supported, that assumption (Box 4). Consequently, decisions large-scale projects where canals were lined with to line irrigation canals must be taken after a sys- geomembranes and seepage rates were dramatically tematic study of the contributions of the seepage to reduced. Despite the experience that conventional BOX 4. FIELD RESEARCH STUDY ON BRICK CANAL LINING PERFORMANCE IN PUNJAB, INDIA The design life for a brick-lined channel is usually assumed to be 20 to 30 years. Lining is expected to reduce seepage from between 200-500 mm/day for earth channels in sandy or clayey loams down to about 50 mm/day for a lined section. Short-term tests on perfect linings in laboratory conditions confirm that seepage rates from lined canals are negligible. However, field studies carried out in Punjab, India in the late 1980s showed that a lined distributary canal was losing 300mm/day within five years of construction, and lined watercourses varying in age from 6 months to 8 years were losing 320 mm/day on average. That is, the observed seepage losses from channels with linings older than four years were comparable to the seepage from unlined channels. The wide gap between laboratory studies and practice arises from the poor quality of construction (quality of bricks, quantity of cement, and compaction of earth behind side walls) combined with wear from people and animals and stresses from repeated drying and wetting caused by rotational water distribution. Source: Goldsmith, H., and Makin, I. (1989). 18 WATER CONSERVATION: IRRIGATION BOX 5. CANAL LINING PROGRAMS IN THE ARIM T BASIN, XINJIANG PROVINCE , CHINA Seepage losses from the irrigation canals and on-farm percolation losses are largely responsible for excessive water use and consequent loss of water to the lower reaches of the Tarim River. The Tarim I project dealt with water resources management issues within two oases only; the Tarim II project, still under implementation, is intended to improve the basin's environment and to partially restore the "green corridor" in the lower reaches of the river which provides a vegetation barrier to encroachment of the Taklimakan Desert. It was projected that the project activities, including canal lining, drainage improvements, and well-field construction (as well as water management improvements) would result in a reduction of 1,000 million m3 in nonbeneficial evapotranspiration. Part of the saved water would be used for increased crop production and part would be used for the green corridor. The Tarim irrigation canals first run on coarse-material lands--with slopes so steep that a high-quality lining is required-- before reaching the irrigable lands with gentle slope and silty soils. The Tarim I project involved lining 980 km of canals, of which 860 km consisted in overlapping thin plastic films (0.2mm) protected with concrete or local materials such as cobble or gravel. This method was considerably improved for the Tarim II project through the use of geomembrane panels (0.5 mm), which are welded in factory and on-site. The Tarim II project includes the lining of 700 km of canals, of which about 400 km were lined with 5 million m2 of geomembranes protected with local materials. Seepage losses of 140 mm/day were measured from a canal lined with plastic film protected with concrete, and 300 mm/day from a canal lined with concrete slabs without plastic film in the Tarim I project. Seepage losses from a canal lined with welded geomembranes in the Tarim II project were reduced to a remarkably low value of 4 to 6 mm/day. Estimated seepage losses from the 57 canals lined during the Tarim I Project were reduced from 1,375 to 405 million m3 and the water savings in the Tarim II project may be in the order of 600 to 800 million m3. The additional cost compared to Tarim I--less than $3 million--makes this improvement the most cost-effective solution to improve the conveyance efficiency of irrigation canals. These results confirm previous observations on the mediocre performance of canal lining techniques that use only rigid materials. The growth of irrigation and decline in environmental quality in the Tarim Basin in the Xinjiang Western Province of China is described in Case Study 1 in Note E.1. lining techniques are not successful over the long ample, water use declined from 12,000 to 6,000 m3 term, the adoption of new technologies such as per hectare within seven years of converting a small geomembranes to line irrigation canals has been project on the West Bank of the Jordan Valley from very slow because of the high cost of importing a surface system with fixed rotation to drip irriga- material in most developing countries and the re- tion. sistance to changes in design standards by many irrigation agencies. Selecting the on-farm distribution and application method that is most suitable for a particular irriga- tion application is important, since the wrong choice FIELD-LEVEL WATER can cause soil erosion, waterlogging, and soil salin- CONSERVATION TECHNIQUES ization. Soil characteristics, topography, and type of crops are the main factors to be considered, with Water losses at farm level vary considerably with the infiltration rate and the water-holding capacity the method of on-farm water distribution and ap- (the amount of water that can be retained in the plication. On-farm water losses with open canal dis- soil for use by the crop) being the two soil charac- tribution networks are estimated to be up to 40 teristics of most concern. percent in unlined ditches. In piped irrigation sys- tems, the water losses range from 10 percent with Water application methods in developing countries localized micro-irrigation and drip to 30 percent with can be broadly divided into surface irrigation and overhead conventional sprinklers (Table 3). For ex- pressurized irrigation techniques. Sub-surface ir- 19 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 TABLE 3. rigated area than at the lower end. Some advanced APPROXIMATE APPLICATION EFFICIENCY OF VARIOUS surface irrigation techniques have been developed ON -FARM IRRIGATION SYSTEMS AND METHODS to minimize the lack of uniformity of irrigation, but System/ Application are not widely used even in developed countries. method efficiency (%)a Surge irrigation, releasing water in furrows for short times separated by closure periods, takes less time Earth canal network; 40­50 surface methods for the water to reach the lower end of the furrow, resulting in a better uniformity of water distribu- Lined canal network; 50­60 tion and higher efficiency. Other techniques, such surface methods as gated pipe and cablegation, were developed to Pressure piped network; 65­75 improve furrow irrigation, but experience shows surface methods they are generally too sophisticated to be used by Hose irrigation systems 70­80 smallholders in developing countries. Low-medium pressure 75 sprinkler systems Adaptive research in the Middle East and North Af- rica has shown the difficulties in introducing sur- Microsprinklers, microjet, 75­85 face water-saving techniques. In Egypt, irrigation minisprinklers trials were conducted with long-level basins and Drip irrigation 80­90 long-level furrows to improve water management, and included precision land leveling. At two sites, aThese efficiency values are indicative. Actual values can range considerably depending on the level of management, the soil the trials were unsuccessful and farmers fared as characteristics, and the method of application. well or better with conventional systems; at the other two sites, the reported net water savings were doubt- ful because drainage and groundwater recycling were not taken into consideration. New irrigation rigation is used in a small number of irrigation development areas in Morocco are subject to land projects in the developed world but has little po- consolidation with the adoption of a geometric lay- tential in the developing world and will not be dis- out of field irrigation and drainage ditches, and pre- cussed further here. cise land leveling for the adoption of furrow or border irrigation in order to improve field efficien- Surface irrigation. Field efficiency will be improved cies. Attempts to introduce gated pipes (uniformly if surface water can be controlled so that the proper spaced outlets for furrows) have failed, likely due amount enters the soil to supply the water needs of to the added expense. Over time, farmers are shift- the crop (plus a leaching fraction if necessary) uni- ing back to the traditional method of irrigation by formly across all parts of the field. Box 6 describes small basins. common surface irrigation methods. Uniformity of water distribution is very difficult to achieve if the Pressurized irrigation techniques. About 20 million land surface is uneven, resulting in low field effi- hectares worldwide are now irrigated by sprinklers ciency, poor crop yields, and soil erosion with con- and 3.2 million hectares are being irrigated by mi- comitant clogging of surface drainage systems. cro-irrigation techniques. Sprinkler irrigation de- Excess water resulting from rainfall or over-irri- livers water in the form of rain drops precipitated gation--if allowed to collect in undrained areas of a over a large area. The equipment for sprinklers field for extended periods--causes deterioration of ranges from hand-moved irrigators and micro- the soil structure and provides breeding areas for sprinklers for small farms to center pivots, linear mosquitoes. moves, and the recently developed LEPA systems (Low Energy Precise Application) for large farms. Even if the land surface is even, more water will LEPA involves drop lines from either center pivot inevitably enter the soil at the upper end of the ir- or linear move systems whereby water is applied 20 WATER CONSERVATION: IRRIGATION BOX 6. SURFACE IRRIGATION METHODS Furrow irrigation is suitable for crops that would be damaged if their stems were submerged. Row crops such as cotton, vegetables, sugar beet, and maize are irrigated by furrow. Considerable experience is needed to divide the water supply into a number of furrow streams and maintain correct rates of flow. Various devices are used for control- ling the flow of water into each furrow. The most popular one is the irrigation siphon type. When water is delivered under low pressure, gated pipes with uniformly spaced outlets are used for releasing irrigation water into furrows. Border irrigation makes use of parallel earth ridges, which guide a sheet of flowing water as it moves down the slope. This method is the most efficient for irrigation of close-growing crops such as alfalfa and pasture. The land must have a uniformly moderate slope. Careful land preparation is necessary. Basin irrigation is the simplest method and most widely used for irrigating crops in developing countries. Many different crops are irrigated by this method. All systems of irrigated rice cultivation make use of basin irrigation. It is possible to modify the soil to decrease the infiltration rate. Compaction and puddling by animals (water buffaloes) has been a traditional method of land preparation in Asian countries. Infiltration rates of 1 or 1.5 mm per day have been consis- tently adopted for the calculation of irrigation water requirements in planning irrigation projects without any field measurement. Basin irrigation can be very efficient for crops other than rice if the basins are supplied with very large flows, as practiced in the United States. at low water pressure directly to the crop to mini- installation. The cost of the solid installations for mize losses from evaporation or wind drift. Micro- localized methods is higher than that of the hand irrigation is characterized by the delivery of water move sprinkler systems. The cost for the installa- at low rates to a limited soil surface area around tion of various piped irrigation systems in Europe the plants. The equipment includes drippers, spray- is presented in Table 4. ers, bubblers, and micro jets. Micro-irrigation sys- tems and micro-sprinklers have the potential to Farmers generally adopt pressurized systems much create significant water savings for smallholder ag- faster than advanced surface application techniques. riculture involved in high-value crops. Micro-irri- For example, about 65 percent of the farmers in the gation has grown by more than six times over the Jordan Valley have shifted from surface to drip irri- last 20 years and, during the 1980s, started pen- gation over a 10-year period, primarily because of etrating developing countries, mainly India and its advantages for water conservation. Farmers built China. small on-farm storage reservoirs lined with plastic sheets to prevent seepage losses and to provide the Both sprinklers and micro-irrigation depend on flexibility required for drip irrigation. water delivery through pressurized pipes. The capi- tal cost of pressurized irrigation systems varies ac- Agronomic improvements. The field efficiency of ir- cording to the method of irrigation and the type of rigation systems can be improved through both ag- TABLE 4. COMPARATIVE COSTS OF PIPED IRRIGATION SYSTEMS (1997 PRICES) Piped Sprinkler Micro-irrigation surface methods hand move solid installation Installation cost ($/ha) $1,400-1,700 $2,100-2,800 $3,000-3,950 Annual maintenance cost ($/ha) $70-85 $105-140 $150-200 21 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 Improved cultivation practices (conservation till- age). Managing the amount, orientation, and distribution of crop and other plant residue on the soil surface year-round conserves soil mois- ture, reduces erosion, and maintains or im- proves soil organic matter. Plastic mulching. Plastic materials can be used to conserve moisture, control weeds, and reduce erosion. IMPROVING THE QUALITY OF IRRIGATION SERVICE The operational performance of the system at all levels of water demand is one of the most impor- tant issues and one that often receives insufficient Bank attention when development or rehabilitation orld ,W projects are being designed. The design must re- Ochs flect not only current requirements but also the alter expected requirements for future operations. W by Photo The choice of the system for water delivery--rota- Spaghetti tube drip irrigation, New Lands Irrigation Area, Egypt tion, arranged schedule, limited-rate demand, and centralized scheduling--will influence the efficiency of water distribution. Most traditional delivery sys- ronomic developments and better control of water tems have no or little flexibility built into them. Thus, application. Overall, the aim is to increase the sharing water on a rigid rotational basis often leads amount of crop produced per unit of water applied. to wasteful use, since users will generally take their Some of the agronomic improvements that conserve full share at each turn irrespective of the water needs water include: of their crops. On the other hand, delivery of water Use of short-duration crop varieties. Some crop on request, also referred to as pre-arranged demand, varieties have shorter growing periods, so less is more likely to improve field efficiency since farm- water is required to produce similar yields. For ers are ordering water only when it is needed. How- example, 120-day rice varieties have now been ever, this method requires the farmers to have replaced by 90-day varieties in most parts of East confidence that their orders will be fulfilled. Asia. Improved crop genetics. Improved crop types The designer of a new or rehabilitated I&D scheme adapted to an area can be selected to minimize must also choose the control strategies and control water use. equipment for the operation of canal irrigation sys- Deficit irrigation.Agronomicresearchhasdem- tems. The selection of a control strategy and equip- onstrated that a reduction of up to 25 percent in ment has a major impact on the ability to provide a irrigation water supply may not substantially high quality of service to users, overall efficiency, affect crop yields, especially cereals, as long as and ease of operation of the system. Potential con- water is delivered at critical growth times. As a trol strategies include local control versus central- result, the number of irrigations of wheat in the ized or supervisory control; upstream versus North China plain has been reduced from five downstream control; or proportional versus adjust- to three. able control. Most projects combine two or more 22 WATER CONSERVATION: IRRIGATION control strategies at different levels of canals. The but requires more design skills and higher quality advantages and disadvantages of the different con- of construction and installation as well as access to trol strategies are discussed in technical publica- skilled operations and maintenance staff for suc- tions.4 cessful long-term operation. Goussard (1993) pre- sents the salient features of the various types of The last step in design is the selection of control control equipment used in irrigation projects. equipment that fits with the selected control strat- egy. Although widely used, manually operated gated Equity considerations should be included with water systems are the most complex to operate if the ob- conservation when new or rehabilitated I&D jective is to provide both quality of service and effi- schemes are being planned, including a water sup- ciency of water use. Automatic control equipment ply that allows tail-enders access to water that is makes it possible to improve service and efficiency consistent with the access of other irrigators. INSTITUTIONAL AND POLICY REFORMS INSTITUTIONAL REFORMS Water rationing User participation in the management of irri- In the 1980s, there was a widespread belief that de- gation systems. ficiencies in management and related institutional Communications strategy. problems, rather than technology of irrigation, were Introduction of water trading within the irrigation the chief constraints in the performance of irriga- sector will tend to improve the economic efficiency tion systems, including poor recovery of investment of the sector but is unlikely to affect overall irriga- and recurrent costs, poor morale and training among tion efficiency. The same volume of water will be staff, and conflicts between farmers and irrigation used, although the value of the products should agencies. It is now accepted that both deficiencies increase with intra-sectoral trading because there in management and institutions as well as techni- is now an incentive to maximize the economic re- cal issues are the causes of poor performance of ir- turns on the water within the sector. If inter-sector rigation projects. Box 7 provides the desirable trading is permitted, then overall irrigation effi- elements for a national water conservation program ciency can improve because of the incentive to trade based on experience in the Middle East. water previously used for low value crops to other sectors where it will achieve a higher return. How- Technical changes need to be combined with insti- ever, basin water use efficiency may not change if tutional and policy reforms to achieve improved inter-basin transfers are not permitted. The example water use efficiency in irrigation projects This is from the Imperial Valley in California (Box 4, Note illustrated by the successful comprehensive mod- E.2) provides an example of inter-sectoral water ernization programs in the Office du Niger in Mali trading. (Box 8). Some of the policy and institutional changes that VOLUMETRIC WATER PRICING have proven to be successful for promoting water conservation include: Prices, which accurately reflect water scarcity val- Price incentives through volumetric pricing ues, will improve water allocation and encourage conservation by giving information to users when they decide to use water. Volumetric charges are fre- quently used for irrigation water pricing in devel- 4See World Bank Technical Paper No. 246. 23 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 BOX 7. DESIRABLE ELEMENTS IN A NATIONAL IRRIGATION WATER CONSERVATION PROGRAM A strong central organization, supported by a comprehensive code of water laws, empowered to plan and design efficient irrigation systems, allocate water, control water use and impose sanctions. Planning, where feasible, of regional or national grids for water distribution and joint operation of both surface water supplies and groundwater resources. For individual irrigation projects, well-founded decisions on the design of conveyance and distribution systems (whether to select pipe or open canal systems or use both systems), taking into account the on-farm irrigation technologies to be promoted. Decisions should be based on long-term water supply and demand projections in the project area, as well as market- ing prospects for crops. Implementing, with the irrigation infrastructure, a comprehensive social and economic development plan for rural areas that promotes the general well-being of the population. Appropriate land reform and land consolidation programs to overcome land tenure problems and improve the efficiency of irrigation layouts and operation (in the main system and on-farm). Implementing a strong research program to develop or adapt on-farm technologies and practices for local condi- tions. A program for testing, demonstrating, and disseminating recommended technologies. A strong irrigation extension service (irrigation advisory service) to advise farmers on irrigation technologies, practices, and scheduling. A strong irrigation agronomy program to assist the irrigation extension service in determining optimal crop water requirements and developing recommendations for new cash crops. A program to train irrigation engineers, technicians, government workers, and water user association workers. An appropriate system of demand management consisting of water metering, water pricing, and possibly water allocations based on carefully researched crop water norms. A system of graduated water prices may be adopted so that the excess use of water is heavily penalized. Strong private sector involvement in manufacturing irrigation equipment and possibly provision of irrigation water. Extension services to the farmers (to be initially supported by the government if necessary). Quality control of irrigation equipment through standardization and issuance of quality marks for locally manufactured products by a national institute of standards. Access to agricultural credit so that farmers can purchase modern irrigation equipment. This may have to be subsi- dized initially, or may contain a grant element to provide sufficient incentive. The promotion of water user associations, especially where the supply of water in bulk would be possible. Source: Van Tuijl (1993). oped countries. Some irrigation districts in Califor- cane and rice. A few countries, such as Morocco nia have instituted incentive pricing rate structures and Brazil, use a two-part tariff for irrigation. For to reduce the application of irrigation water, such example, Brazil imposes a fixed charge to recover as tiered pricing. Under tiered pricing, volumetric investment costs, and a variable part calculated to water rates are increased considerably for volumes cover the operation and maintenance cost of the exceeding a certain ceiling. project. This approach has the advantage that there is a guaranteed income for the irrigation organiza- Measuring water volumes is expensive and prone tion from the fixed part even when the variable part to interference by landowners. Consequently, in is negligible because of either a wet year (and hence most developing countries, water is charged per unit no need to irrigate) or a dry year (when little irri- of irrigated land. In some countries, the unit rate gation water is available). This avoids the budget- varies with the type of crops, reflecting the higher ary problems that arise when pure volumetric average consumption of some crops such as sugar charging is used. 24 WATER CONSERVATION: IRRIGATION BOX 8. OFFICE DU NIGER, MALI: FROM FAILURE TO SUCCESS The Office du Niger, created for cotton cultivation in the 1930s, was managed by a government-owned company. For many years, the Office du Niger was an example of a centralized irrigation system with a heavy financial burden. In the 1950s, cultivation of cotton was abandoned and replaced by rice paddies because of the rapid increase in waterlogged conditions. The Office had a monopoly on buying crops, resulting in low farm gate prices. Under these conditions, there was little incentive for farmers to pay their water fees. O&M was neglected and the system was steadily breaking down. It was only maintained by direct government support. A consensus was reached during the 1980s by all parties that the system had to be reformed. The monopoly was removed and farmers were given a role in the decisionmaking. Office expenditures were made transparent. The Office now concentrates on the essential functions of water services, planning, and maintenance. The paddy management and commercialization functions of the Office du Niger were progressively privatized. Water fee collection rates are now close to 100 percent in the well-rehabilitated zones. Modern water control systems were installed for the main conveyance of the distribution network and the paddy land was precisely leveled. These technical improvements made it possible to adopt high-yielding rice varieties, resulting in an increase of paddy yields from 1.5 to 6 ton/ha. Water use dropped from 1,500 m3/ton to 250 m3/ton, a 6-fold improvement in water use efficiency, leading to a decrease in the volume of water diverted for irrigation. This restructuring of the Office made it possible for the agro- nomic and economic performance of the project to improve dramatically. Source: Couture, J.L. and P. Lavigne, 2000. Institutional Innovations and Irrigation Water Management in Office du Niger, Mali (1910-1990). World Bank Workshop on Institutional Reforms in Irrigation and Drainage; G. Diemer, 2002. Reform of Governance of the Office du Niger in Mali, International Network on Participatory Irrigation Management No 12, October 2002. Some countries do not apply water charges because Latin America countries, including Mexico, Colom- of cultural traditions--in some Islamic countries, bia, Brazil, and Argentina. In most parts of China, water is regarded as a gift of God--or because water water delivery is based on scheduling that is pre- charges are assumed to be included in other taxa- established with stakeholders. tion mechanisms such as land taxes (Indonesia and Thailand). In the 1970s and 1980s, a number of donor-financed projects supported the installation of simple mea- Methods of water charging that are not based on suring devices--such as staff gauges, weirs, or flumes-- the volume of water delivered will have little or no at the farm or group level to improve the management impact on water conservation. Raising irrigation of canal irrigation systems. Today, most of these de- water fees does not provide an incentive to conserve vices are not used and/or are not in working condi- water. To the contrary, an increase in water charges tion because of the manpower required for the may give the impression that irrigators are entitled repetitive reading of these manual devices. Addition- to use more water because they are paying more. ally, these devices could only measure the flows, whereas in practice volumetric pricing requires de- Charging for the volume of water consumed requires vices that can both measure and control the flow of both physical and institutional infrastructure to be water, or at least total the volumes delivered. feasible and effective. Volumetric water charging requires a) the measurement of volumes of water In principle, it is easier to measure volumes used used in order to assess charges; and b) the delivery in pressurized irrigation systems using commer- of the water on a pre-arranged demand or on ac- cial meters with totalizers of volumes, similar to tual demand. Both conditions are rarely met in most those used in the urban sector. However, in some large-scale public irrigation systems (Box 9). Most projects, many of these devices become damaged if irrigation systems around the world have not been they are not under the responsibility of individual designed to adjust the delivery of water to the real- farmers, making it impossible to levy individual time demand of individuals or groups of farmers. water charges. In the modernized Jordan Valley Water is delivered on pre-arranged demand in most project, volumetric charges are applied, but water 25 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 BOX 9. VOLUMETRIC WATER MEASUREMENT IN MOROCCO User-friendly measuring devices, known as modular baffle distributors, that are insensitive to fluctuations in upstream water levels have been installed in surface irrigation projects in Morocco and other Mediterranean and Middle East countries. These devices only require readings of timings of opening and closings of constant-flow gates in order to calculate volumes. In Morocco, the project authorities generally use a fixed rotation for water delivery. The fixed rotation system was introduced when the schemes were set up because many of the farmers were new to irrigated agriculture and needed a simple water delivery method. Since the only option for users is to either take their turn in the imposed weekly rotation or forgo it, there is little incentive for water conservation in spite of the volumetric charging. These modern canal irrigation projects apply volumetric water charges and have the capacity to deliver water on pre- arranged demand. However, this capacity is not utilized. To assess water bills in some sprinkler-irrigated areas in Morocco, the total volume measured at the pumping stations is divided between all the users, since the individual meters are generally not in working condition. Thus, Morocco is in the unusual situation of applying volumetric pricing to surface irrigation but not to pressurized systems where, in theory, it should be simpler to introduce. is delivered on a rotational basis to control the use direct interest in efficiency and flexibility of water of very scarce resources, since the present water delivery because of their influence on profitability. rate is too low for volumetric charging to have any Users would also be more likely to pay for the costs effect on water consumption at the farm level. Con- of I&D systems if they had influence over its opera- sequently, this low-price, volumetric charging has tions, and their involvement in the management of no effect on water conservation. I&D schemes would provide an opportunity to im- prove conservation of water. Volumetric wholesaling of water from main canals to user groups provides a compromise between areal By the mid-1980s, several countries started to imple- based and volumetric charges. Volumetric whole- ment irrigation management programs in which saling to user groups is particularly effective be- irrigators were encouraged to participate in opera- cause the farmers are collectively responsible for tion and maintenance activities. Box 10 discusses paying for the water, and so they conserve and eq- two types of user associations. In Asian countries, uitably distribute water within the user group, of- such as the Philippines, Indonesia, and Pakistan, ten without individual measurements. such programs consisted of a large-scale transfer of the lower level of canal irrigation systems to user WATER RATIONING groups, each one covering a few hundred hectares (from 50 to 200 hectares). Water rationing can have an immediate effect when annual or seasonal allocations exceed the irriga- Participatory irrigation management took a differ- tion crop requirements. Thus, irrigation deliveries ent orientation in the late 1980s with the implemen- for cotton cultivation in Uzbekistan were reduced tation of the 2-phase transfer programs in Mexico. from about 17,000 to 13,000 m3/ha in the early 1990s In a first phase, now completed, user associations without any significant effect on the crop yield. took over the financial and managerial responsi- bilities for operating the irrigation systems below PARTICIPATORY IRRIGATION the main canals. These associations cover areas MANAGEMENT ranging from 5,000 to 25,000 hectares. In the sec- ond phase, the responsibilities for managing the Public irrigation management organizations have main canals are being handed over to limited- little incentive to improve the performance of irri- responsibility companies. The success of the trans- gation projects. On the other hand, users have a fer program in Mexico has encouraged other coun- 26 WATER CONSERVATION: IRRIGATION BOX 10. SOCIAL AND BUSINESS USER ASSOCIATIONS User associations can be formed as either "social" and "business" groups. The business associations are responsible for water distribution, fee collection, maintenance, conflict resolution, and representation of farmers in discussions with public agencies. These associations are legal entities that can enter into contracts. They have the power to enforce rules and regulations. The farmers are not directly involved in the management of their I&D systems; these associations hire professional staff for the actual management. On the other hand, members of social associations are expected to be involved in maintenance activities of the lower level of canal systems, and in some cases to assist government agencies in collecting irrigation service fees. Many of the business associations have modernized their maintenance and administrative activities through acquisi- tion of specialized equipment. They have also dramatically improved the collection rates of water charges. tries, such as Turkey, to adopt the same approach and that physical and institutional improvements with similar success. in irrigation need to be designed in a coordinated manner. Thus, the introduction of volumetric charg- Despite the widespread adoption of water user in- ing requires that the monitoring equipment and con- volvement programs, there is still little informa- trol techniques that are installed need to be tion about their impact on the performance of commensurate with the staffing and skill levels of irrigation systems or on water conservation. Busi- the irrigation authority. ness-type associations have been much more suc- cessful than government agencies in recovering COMMUNICATIONS STRATEGY annual costs through higher charges and higher collection rates, and maintenance activities by the An effective communications strategy can serve a associations have stopped the deterioration of in- useful purpose--to instill positive attitudes and be- frastructure in these systems. Nevertheless, the havior changes--that can contribute to successfully impact is not noticeable in terms of agricultural implementing a water conservation program. It can production, at least for projects that were previ- contribute to a better understanding of institutional ously managed by irrigation agencies according to reforms and technological intervention by the wa- well-established rules. ter users, and facilitate greater participation of the stakeholders in the design and implementation of Some projects that were performing at a low level water conservation programs. Since the stakeholder of efficiency before the transfer of responsibilities interests are varied, an effective communication to user organizations have claimed a substantial strategy needs to be able to reach and engage stake- increase in agricultural productivity. For example, holders through, but not limited to, processes in- in the state of Andhra Pradesh, India, the irrigated volving consultations and communication in order areas in individual schemes increased by between to disseminate information, build consensus, and 5 to 10 percent after statewide irrigation reforms, encourage sustainability of the reforms among including the creation of user organizations, were stakeholders. Important elements of a good com- introduced in 1997. munications strategy are that it must be culturally sensitive, acceptable, and context specific for effec- Overall, the experience of the last 20 years shows tive dissemination of information on the broader that most institutional improvements are not fully water sector reforms and how water conservation effective without the right physical environment, plays a central role in the reform process. 27 WATER RESOURCES AND ENVIRONMENT · TECHNICAL NOTE F.2 CONCLUSION Agricultural water use will continue to dominate nological improvements or policy changes is par- as the largest worldwide water user in the future ticularly desirable. However, the effect of water and so major water savings are most likely to come conservation on downstream water uses and the from improved efficiencies in agriculture. These will preservation of aquatic life and wetlands in coastal require the application of both technical and insti- areas must be factored into these decisions. tutional improvements. However, in all cases, wa- In areas where there is potential for the reuse ter conservation in irrigation needs to be undertaken of seepage water or runoff losses elsewhere in as part of basin-wide decisionmaking. Thus: the basin, the solutions to conserve water in the In areas where there is little return flow or little upstream areas have to be traded off against groundwater recharge to be reused by down- reduced water supplies to other users within stream users, water conservation through tech- the irrigation areas. FURTHER INFORMATION Good general discussions of irrigation water effi- Good references on canal lining include: ciency include: Goldsmith, H., and I. Makin. 1989. Canal Lining: From Plusquellec, H. (forthcoming) How Design, Policy and the Laboratory to the Field and Back Again. Lon- Management Affect Performance of Irrigation don: Overseas Development Unit. Projects. Rome: FAO. Kraatz, D. 1977. Irrigation Canal Lining. Rome: Food and Seckler, D. 1996. The New Era of Water Resources Man- Agriculture Organization (FAO). agement. Research Report 1. Colombo, Sri Lanka: International Water Management Institute Irrigation system operations are discussed in: (IWMI) Jensen, M. 1993. "The Impacts of Irrigation and Drain- Goussard. 1993. Automation of Canal Irrigation Systems. age on the Environment." Gulhati Memorial Lec- New Delhi, India: International Commission on ture. ICID Congress. The Hague. Irrigation and Drainage (ICID). Regional experience in water conservation in irri- Field level water conservation techniques are dis- gation is described in: cussed in: Amer, M. H., and N. A. de Ridder, eds. 1989. Land Drain- Mei Xie, U. Kuffner, and G. Le Moigne. 1993. Using Water age in Egypt. Cairo: Drainage Research Institute. Efficiently: Technical Options. World Bank Tech- Van Tuijl. 1993. Improving Water Use in Agriculture: Ex- nical Paper Number 205. Washington: World periences in the Middle East and North Africa. Bank. World Bank Technical Paper Number 201. Wash- Phocaides, A. 2001. Handbook on Pressurized Irrigation ington: World Bank. Techniques. Rome: Food and Agriculture Orga- Galand, A., M. Terrazoni, and C. Fayollet. 1997. Approche nization (FAO). des uages Globaux en Basse Durance. Water: Economics, Management and Demand. ICID. Proceedings of the 18th European Regional Con- ference "Water an Economic Good?", Oxford, UK, September 1997. 28