coping with water scarcity: water saving and increasing water productivity

IRRIGATION AND DRAINAGE

Irrig. and Drain. 52: 3–20 (2003)

Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/ird.73

COPING WITH WATER SCARCITY: WATER SAVING AND INCREASINGWATER PRODUCTIVITY†

A. HAMDY,1 R. RAGAB2* AND ELISA SCARASCIA-MUGNOZZA3

1 CIHEAM/Mediterranean Agronomic Institute, Bari, Italy2 Centre for Ecology and Hydrology, Wallingford, UK

3 Italy-ICID, Rome, Italy

ABSTRACT

The increasing scarcity of water in dry areas is now a well-recognized problem. According to the WorldCommission on Environment and Development, approximately 80 countries with 40% of the world populationalready suffer from serious water shortages.

At present, water shortages have led most of arid and semi-arid countries to increase food imports becausethe local agricultural sector is not able to produce sufficient food to fill the existing food gaps. The increasingfood gaps are posing serious challenges beyond the economic and political capacity required for the necessaryadjustments concerning the allocation and use of water in all sectors, particularly agriculture.

The agricultural sector is by far the largest user of water in the world. On a consumptive use basis, 80–90%of all the water is consumed in agriculture. Unfortunately, water use efficiency in this sector is very poor notexceeding 45% with more than 50% water losses; thereby, enormous water saving could be achieved in theagricultural sector comparable with other sectoral water uses.

The growing water scarcity and the misuse and management of the available water resources are nowa-days major threats to sustainable development for the various sectors, especially domestic, industrial andagricultural.

Today, in most countries suffering water shortages, at the heart is the question of whether a water crisiscan be averted or whether water can be made productive. Increasing the productivity of water is central toproducing food, to fighting poverty, to reducing competition for water and to ensuring that there is enoughwater for nature. The more we produce with less water and/or with the same amount of water, the less theneed for infrastructure development, the fewer the conflicts among the sectoral water uses, the greater thelocal food security and the more water for agricultural, household and industrial uses, and the more thatremains in nature. However, to achieve such goals, major improvements are still required in water resourceuse and irrigation technology and management. Meeting such challenges will require a far greater effort andsignificant changes in how water is managed. What needs to be changed? What are the improvements requiredto cope with increased water scarcity?

These are the issues to be discussed in this paper: addressing the appropriate techniques and proper tools tobe adopted for increasing the productivity of water through water saving, and improving the rates in water useefficiency in the irrigation sector coupled with better management systems for water conveyance, allocationand distribution. Copyright 2003 John Wiley & Sons, Ltd.

KEY WORDS: water scarcity; water saving; water productivity; irrigation; water use; water management

* Correspondence to: R. Ragab, Centre for Ecology and Hydrology, Maclean Building, Crowmarsh Gifford, Wallingford, OxfordshireOX10 8BB, UK. E-mail: [email protected]† Comment faire face a la penurie d’eau: economie de l’eau et accroissement de sa productivite.

Copyright 2003 John Wiley & Sons, Ltd.

Received 2 September 2002Revised 5 November 2002

Accepted 19 November 2002

4 A. HAMDY ET AL.

RESUME

La penurie en eau croissante dans les zones arides est desormais un fait reconnu. Suivant la CommissionMondiale de l’Environnement et du Developpement, approximativement 80 pays avec 40 pour cent de lapopulation souffrent deja de graves problemes de penurie d’eau.

A l’heure actuelle, la penurie d’eau a oblige la plupart des pays arides et semi-arides a accroıtre lesimportations des produits alimentaires car le secteur agricole local n’est pas en mesure de satisfaire la demandealimentaire. Le deficit alimentaire pose des defis qui vont au-dela de la capacite politique et economiquerequise pour les ajustements necessaires pour l’allocation et l’utilisation de l’eau dans tous les secteurs, etdans l’agriculture en particulier. Le secteur agricole est de loin l’utilisateur le plus important dans le monde.Se referant a la consommation en eau par evapotranspiration, 80 a 90% de l’eau est utilisee en agriculture.Malheureusement, l’efficience d’utilisation de l’eau est tres faible et n’excede pas 45% avec plus de 50%des pertes, ce qui fait que c’est dans le secteur agricole plus qu’en d’autres secteurs qu’on peut realiser uneeconomie d’eau considerable.

La penurie d’eau croissante et la mauvaise utilisation et gestion des ressources en eau disponibles sont, al’heure actuelle, les principales menaces au developpement durable dans les differents secteurs, surtout lessecteurs menager, industriel et agricole.

A l’heure actuelle, dans la plupart des pays qui souffrent d’une penurie d’eau, on s’interroge si une crisehydrique peut etre annoncee ou si l’on peut accroıtre la productivite de l’eau. Une meilleure productivitede l’eau est un point crucial pour la production alimentaire, pour la lutte contre la pauvrete, pour reduirela competition et assurer une disponibilite en eau suffisante en nature. D’autant plus nous produisons avecmoins d’eau et/ou la meme quantite d’eau, d’autant plus faible sera la necessite de developper de nouvellesinfrastructures, d’autant plus reduits seront les conflits entre les usages sectoriels, d’autant meilleure sera lasecurite alimentaire locale et d’autant plus elevee sera la quantite d’eau disponible pour l’usage agricole,municipal et industriel, et d’autant plus grande sera la quantite d’eau disponible en nature.

Pour realiser ces objectifs, il faut encore ameliorer considerablement l’utilisation des ressources en eauainsi que la technologie et la gestion de l’irrigation. Pour repondre a ces defis, il faut un effort majeur et deschangements significatifs dans la maniere de gerer l’eau, dans les adaptations des besoins et les ameliorationsnecessaires pour faire face a la penurie d’eau.

Ce travail s’occupe de ces aspects et porte en particulier sur les techniques appropriees et les outils adequatsqu’il faut adopter pour accroıtre la productivite de l’eau a travers l’economie de l’eau et l’amelioration deson efficience d’utilisation dans le secteur de l’irrigation associees a un meilleur systeme de gestion pour letransport, l’allocation et la distribution de l’eau. Copyright 2003 John Wiley & Sons, Ltd.

MOTS CLES: eau; penurie; economization; productivite; irrigation; utilisation d’eau; gestion d’eau

INTRODUCTION

The availability of fresh water is one of the great issues facing humankind today, in some ways the greatest,because problems associated with it affect the lives of many millions of people. During the next 50 yearsproblems associated with a lack of water or the pollution of water bodies will affect virtually everyone onthe planet. Water shortages and needs are increasing, and the competition for water among urban, industrial,and agricultural sectors, as well as other resources users, is growing more intensive.

Population in the developing world is increasing, leading to growing demands for water resources and,unfortunately, to more pollution which effectively reduces the availability of water to meet human needs.

Huge investments in water infrastructure have not met the demands of the developing world. We can thinkback on major investments in water systems, wastewater disposal and irrigation systems, but these have notmet local needs. In addition, institutional weaknesses have posed serious threats to long-term sustainabilityin the development of the water sector and, generally, the problem stems from infrastructure inadequacies aswell as from resource mismanagement.

Copyright 2003 John Wiley & Sons, Ltd. Irrig. and Drain. 52: 3–20 (2003)

COPING WITH WATER SCARCITY 5

Many agricultural production systems, including irrigated agriculture, perform poorly. In many places,projects not properly formulated, implemented and managed have caused misallocations of water—or itssheer waste—and have led to the degradation of land. Potential physical, social and environmental impactswere not identified, and even if they were, mitigating measures like the timely installation of drainagecomponents to prevent waterlogging and salinization were simply neglected, as was the formation of waterusers’ organizations.

At present, due to the increasing water scarcity, food security in most developing countries is very doubtful.In this regard, the following two fundamental questions are asked: What should be done? And what is theappropriate balance between supply-side and demand-side water strategies?

Concrete answers to such questions are not available. There is thus a need to deal with the management ofland and water resources within a comprehensive framework in which policies can be formulated and projectscan be planned for their subsequent integrated implementation. Management needs to be improved, both atthe level of the farmers and that of the irrigation system. In practice, these improvements will continue toprove hard to realize, and they will require more time than improvements in the physical infrastructure.

This paper addresses the efforts to be made to increase the productivity of water through appropriate watermanagement, water saving and improving the rates in water use efficiency in the irrigation sector.

WORLD POPULATION AND FRESHWATER USE, 1940–2000

The world’s population grows by more than 90 million each year. In just 30 years, by 2025, it may be 50%more than it is today—the largest population growth ever seen in such a short time. If the current trends ofpopulation and economic growth continue, the world will have 1 billion more people than it had in 1990,more than half of the developing countries will be unable to feed their people without importing food andone-fourth of the world’s freshwater supply would be too polluted to drink. The new century will face anuphill task of feeding the large growing population with limited natural resources. The evolution of worldpopulation and annual water used is given in Figure 1.

During the past decade, drinking water has been made available to 1.2 billion people, and 770 million havegained access to safe sanitation. While the population grew threefold in this century—from 1.6 billion tomore than 5 billion—irrigated agriculture grew fivefold to some 240 million ha, meeting only 16% of theglobal food security.

0

1

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5

6

7

1940 1950 1960 1970 1980 1990 20000

1000

2000

3000

4000

5000

6000

7000

Annual Water Use

Population[billion]

Population

Annual Water Use[cubic kilometers]

Figure 1. World population and annual water use


6 A. HAMDY ET AL.

PROJECTED WATER USE

Because of population growth, between 2000 and 2025 the global average annual per capita availabilityof renewable water resources is projected to fall from 6600 m3 to 4800 m3. Given the uneven distributionof these resources, however, it is much more informative that some 3 billion women and men will live incountries—wholly or partly arid or semi-arid—that have less than 1700 m3 per capita, the quantity belowwhich one suffers from water stress (Cosgrove and Rijsberman, 2000).

Table I shows two diverging water use projections for 2025. The projection by Shiklomanov (1999) isbased on the assumption that current trends can be extrapolated—that reservoirs will be constructed as in thepast and that the world’s irrigated area will expand by 30% from 1995 to 2025. This projection is supportedby the FAO, ICID and the International Water Management Institute (IWMI) first projection (Seckler et al.,1998). The conclusion of their analysis under optimistic assumptions on yield and efficiency improvementsis that the irrigated area will expand by at least 17% from 1995.

The projection by Alcamo et al. (1999) assumes limited expansion of the irrigated area, which, combinedwith rapidly increasing water use efficiency, leads to reduced agricultural use but a rapid increase in municipaland industrial use linked to rising income and population.

This perspective is supported by environmentalists and by a number of stakeholders in agriculture; it holdsthat a slowdown in dam building and irrigation investments, combined with the consequences of fallinggroundwater tables, will limit the expansion in irrigated area to 5–10%.

The key difference between these two projections—the amount of increase in irrigated land—is the firstturning point. Even though water use goes up significantly in both projections, neither scenario is based onsatisfying the world’s water and water-related basic needs, particularly for food production and household use.

Analysis of the two alternatives shows that neither is attractive:

• unattractive alternative 1. The 30% increase in irrigated area requires major investments in water infrastruc-ture, a considerable part of which would have to be through large dams. There would also be severe water

Table I. Two diverging projections for use of renewable water resources for businessas usual (m3)

Use Expanding irrigation Stable irrigation

1950 1995 2025a 2025b

AgricultureWithdrawal 1100 2500 3200 2300Consumption 700 1750 2250 1700

IndustryWithdrawal 200 750 1200 900Consumption 20 80 170 120

MunicipalitiesWithdrawal 90 350 600 900Consumption 15 50 75 100

Reservoirs (evaporation) 10 200 270 200c

TotalWithdrawal 1400 3800 5200 4300Consumption 750 2100 2800 2100

a Shiklomanov projection.b World Water Vision business as usual scenario. Alcamo projections.c Alcamo et al. do not calculate reservoir evaporation, but since the business as usual scenariodeveloped by the World Water Vision assumes that relatively few additional reservoirs will bebuilt, Shiklomanov’s 1995 estimate is used to obtain comparable total use figures.Sources: Shiklomanov (1999); Alcamo et al.(1999).Note: all numbers are rounded.



scarcities and serious risks of major damage to ecosystems (Shiklomanov, 1999; Seckler et al., 1998); and• unattractive alternative 2. A strong reduction in irrigation expansion—under otherwise unchanged policies,

or business as usual as elaborated by the Scenario Development Panel (Alcamo et al., 1999; Rosegrant andRingler, 1999; IWMI, 2000)—will cause considerable food shortages and rising food prices.

Both “unattractive and unsustainable” alternatives would considerably deepen today’s water crisis. Thusthere is every motivation to implement policies that make food production and water resource managementmore sustainable.

CONTRIBUTION OF IRRIGATION TO FOOD PRODUCTION

During the past four decades, irrigation and drainage have contributed significantly to the increase in foodproduction. Today, one-sixth of cropped land that is irrigated produces one-third of the world’s harvest offood crops. Drainage has enhanced the productivity of another tenth of cropped lands.

The contributions are not without costs. Irrigated agriculture consumes 70–80% of the fresh water usedin the developing countries. Drainage of agricultural land has impacts on downstream water quality. Furthergrowth in irrigated agriculture will be limited by the scarcity of water and land, by increasing competitionfor water, by the degradation of the environment, by the rising cost of development, by the deterioration ofexisting systems, and, finally, by the inadequacies of management.

According to the 1992–93 World Resources Report, by the year 2000, the total irrigated area is expectedto increase by about 19% and to accommodate that increase, water withdrawals for irrigation are projectedto increase by almost 17%. The changes in the functional use of water will occur mainly in Asia, Africa andLatin America.

In 1993, approximately 1.45 billion ha of the world’s crop land, or 3% of the earth’s surface, was used byagriculture which was responsible for 65–70% of all water withdrawals (WRI, 1996; WWI, 1996).

There are great regional variations, in terms of both absolute withdrawal and per capita consumption inthe amount of water withdrawn by agriculture (Table II). Continents where more than 80% of all waterwithdrawals are for agriculture, such as Africa and Asia, contrast with Europe and North America, whereagriculture accounts for only 39 and 49% of the total withdrawals respectively. In arid and semi-arid devel-oping countries more than 90% of all water withdrawals is for agricultural purposes, whereas in humid regionsthe figure is only 30%.

FOOD AND WATER CONSUMPTION: CURRENT SITUATION AND A LOOK INTO THEFUTURE

Between 1965 and 1985 more than 50% of the increased yield in global food production was achieved byirrigated agriculture (WRI, 1996). Irrigated crops amounted for 40% of global food production. The total area

Table II. Annual continental water withdrawals by agriculture

Year Totalwithdrawal

(km3)

Per capitawithdrawal by

agriculture (m3)

Withdrawal by agriculture(percentage of total

withdrawals)

Africa 1995 145 175 88Asia 1987 1633 460 85Europe 1995 455 244 31North America 1995 608 711 49South America 1995 106 196 59Oceania 1995 17 199 34

Source: WRI (1996).


8 A. HAMDY ET AL.

of irrigated land has risen fivefold in the last 100 years, from approx. 50 million ha in 1900 to 95 million hain 1950, to approx. 250 million ha in 1994. Over the same period, water withdrawals for irrigation landincreased even faster, by a factor of six (Table III).

Grain crops account for around 50% of the world’s cultivated land. One can assume that about 1000 tof water is needed to produce a single tonne of grain (WWI, 1996). This figure includes transpiration fromplants and evaporation from soils, but not the losses due to wasteful irrigation methods or the water needed todesalinate the soil. Thus, the quantity of water referred to is more a reflection of minimum requirements forgrain production. Based on world grain production of 1.72 billion t in 1995 (FAO, 1996), a water volume of1720 km3, or 300 m3 per capita, is required. The quantity of grain produced worldwide in 1995, i.e. 300 kgper capita, corresponds to exactly the amount necessary to cover the calorie needs of the population. Given100% efficiency and a diet consisting of plant foods, only 300 m3 of water per capita and annum wouldtheoretically suffice to supply the world with food. Current consumption of grain is around 150 kg per capitaand annum on a worldwide average and therefore meets only half of humanity’s calorie needs (2200 kcal perperson per day).

Based on the above-mentioned water consumption, an additional 51.3 billion m3 (51.3 km3) of waterannually is needed to cover the additional food needs for the growth in population of 90 million people.Given a constant average per capita consumption of food, an additional 1556 billion km3 of water will berequired for food production in the year 2025. This is 18 times the quantity of water that flows down theNile every year, or 58% of the volume that was used in agriculture in 1990. These figures do not take intoaccount the water losses due to inefficient irrigation. If present production conditions in irrigation farming areapplied to the year 2025, water withdrawals for food production would rise by a further 20% to 1867 billionkm3 (World Water Forum, 2000).

THE CHALLENGES

We now face the challenge of feeding 8 billion people by the end of the first quarter of the twenty-first century.The United Nations medium growth projection will expand from present 6 billion to nearly 8 billion in

2025. More than 80% of these people will live in developing countries. This implies that on nearly the samewater and land resources base, we must grow food for 2 billion more people as well as supplying expandingdomestic and industrial water use.

Experience leads us to the fact that to feed 2 billion people water supplies used in agriculture will have tobe augmented by an additional 15–20% over the next 25 years, even under favourable assumptions regardingimprovements in irrigation efficiency and agronomic potential to meet food requirements. This will amountto an additional 0.6–0.7% of water supply per year.

Table III. Agriculture’s share of global water withdrawals, 1900–95

Year Withdrawals byagriculture (km3)

Totalwithdrawals (km3)

Proportion(%)

1900a 525 578 911940a 893 1057 841950a 1130 1367 831960a 1550 1985 781970a 1850 2586 721980b 2090 3020 691987b 2235 3240 691995c 3106 4145 75

Source: compiled from Clarke(1993)(a); WRI (1994, 1996)(b); Alcamo et al.(1997)(c).



This leads us to ask what are the options and tools to be implemented that could bring reasonable answersto meet our future water and food needs.

OPTIONS AND TOOLS

There is no single solution for sustainable use of water resources in irrigated agriculture.In order to survive the consequences of water scarcity, approaches have to be undertaken by professionals

such as:

• strictly manage the demand for precious resources, preserve and augment the supply or more preferablyto combine the previous two options in an integrated management plan aiming ultimately at sustainabledevelopment;

• effective water-saving programmes and strategies in all water use sectors and, particularly, agriculture;• increasing water productivity; and• the reuse and recycling of non-conventional water sources as additional ones.

Our attempt here is to outline key issues that warrant our priority attention as we seek to move from acommon understanding of the problems to concrete actions to be implemented.

WATER RESOURCES MANAGEMENT: A NEW APPROACH

Why do we need a new approach to water resources management? Quite simply, it is clear that in manycountries, existing approaches are not sustainable in the physical, economic, or environmental sense mainlybecause:

(a) water is misallocated—low-value uses consume a significant share of the resource, while high-value usessuffer shortages;

(b) water quality is not monitored, leading to inappropriate use of low-quality water and to long-term effectson land and groundwater quality;

(c) water and sewage services, especially for the poor, are inadequate;(d) costs of new water development are mounting drastically.

These issues cannot be addressed by the present fragmented approach to water resources since it leads toinappropriate investments in the different water subsectors, and prevents adequate consideration of alternativeuses of water, water conservation, and environmental effects.

Integrated water resources management (IWRM) is an alternative approach, one that is now endorsed byinternational agencies (Delft 1991; Dublin 1992). The UN Conference on “Environmental and development”in Rio de Janeiro in June 1992 concluded that “the holistic management of fresh water as a finite and vulnerableresource, and the integration of sectoral water plans and programs within the framework of national economicand social policy, are of paramount importance for actions in the 1990s and beyond”.

In order to move from fragmented sectoral water management to a holistic integrated management, newsolutions must be found. However, if these solutions are to be sustainable, countries need to strengthen thecapacity to undertake IWRM exercises on a periodic basis. Countries as well as their external support agenciesare used to operating on a subsectoral basis, developing projects in water supply, irrigation and hydropowerwithout regard to the intersectoral effects.

The principles of IWRM include a comprehensive analytical framework coupled with decentralized manage-ment of water resources and the active participation of water users. The analytical framework requires theexamination of water resources, usually with a river basin as the spatial unit, by considering potential uses andpossible effects, especially environmental effects. Protection, enhancement, and restoration of water quality,


10 A. HAMDY ET AL.

plus abatement of pollution, are principles which must satisfy each of the aspects of comprehensive watermanagement mentioned previously.

A comprehensive analytical approach does not mean comprehensive planning; it is not intended to makerigid, centralized prescriptions. Decentralizing the actual management has many benefits, among which ishelping the public sector better perform the needed functions of regulation. The participation of key stake-holders is necessary at the stage of analysis to account for all effects and externalities and also in managementto ensure the sustainability of the systems.

The comprehensive approach also relies on appropriate incentives for providers and users of water. Theseare necessary if we are to allocate water to the best possible use and price water services properly to fosterfinancial discipline and accountability among water providers and users.

IWRM calls for a new approach and, therefore, requires new analytical capabilities on one hand, and onthe other new skills to facilitate the participation of stakeholders in the process. For such an exercise to besuccessful, country capacity to formulate IWRM strategy needs to be strengthened. It is, therefore, importantthat IWRM strategy formulation must be seen, not as a one-shot effort carried out by external experts, butas an iterative exercise in analysis and management. Ownership of any programme in the sector by thedecision-makers and participation by key stakeholders are crucial to its success.

The introduction of IWRM offers the greatest opportunities for people to reach beyond their particularsubsector and discipline. It calls for intensive interaction between subsectors and disciplines. Irrigation special-ists have to talk with water supply and environmental experts. Technical specialists have to communicate withsocial scientists. In particular, if engineers and technical professionals are to be at the policy table to addresssustainable development, it is important that they cross narrow specialist boundaries. To be present at thepolicy table requires a broad understanding not only of the interaction of technical areas in water manage-ment, but of the processes by which policies are made and implemented, and how conflicts over water canbe resolved or—better yet—avoided.

DEMAND MANAGEMENT AS A NEW CHALLENGE FACING IRRIGATED AGRICULTURE

Traditionally, the response to water shortage in arid and semi-arid regions has been addressed through devel-oping more supplies. But as the uses of water have changed and expanded, and as more accessible resourceshave been fully exploited, so the costs for further supply-side options have increased dramatically. Even,water-rich countries are finding it increasingly expensive, in some case prohibitively so, to resort to large-scale infrastructural solutions for providing water to meet increasing demands. Furthermore, in addition todirect investment costs, issues related to settlement of population and to adverse effects on nature have becomemore difficult and more expensive to overcome.

Such concerns add weight to major changes in the approach to water resource management supplies, if thechallenges of imbalance between usable water supplies and demands are to be overcome.

There is very little that can be done with the supply side of the water equation which at the moment isheavily unbalanced, and the option is to manipulate the demand side.

DEMAND WATER MANAGEMENT

There is no question of the central importance of demand management, particularly in the agricultural sector.There is much concern in the regions suffering water shortage that irrigated agriculture will first and

disproportionally be affected by increasing water scarcity and growing demand by other sectors. Agriculturewill indeed have to compete with higher-value uses, if market mechanisms are permitted to come into play.The World Bank comes to the conclusion that in the light of the high opportunity cost of water and thelack of economic opportunities to increase supply on a large scale, agriculture will inevitably have to releasefreshwater resources to other sectors of the economy over the long term. Most of the water savings to meet thegrowing water demand in the municipal and industrial sector would be made in the agricultural sector. This



is not only because irrigation takes the highest share of total water use, but also because it has considerablepotential for efficiency improvement. In typical traditional irrigation schemes, as little as 45% of applied watermay be used by crops with losses as high as more than 50%. Assuming a typical situation where 80% of totalwater use is for agriculture, a 10% increase in the efficiency of irrigation would provide 50% more water formunicipal and industrial use. This is a good illustration of the potential for water savings in agriculture andthe need to press for it (Hamdy and Lacirignola, 1999).

We need to introduce the concept of demand management into water policies, programmes and actionsin particular with irrigation as the main consumer, with major water losses, thus, huge water saving, couldbe realized.

COPING WITH THE CHALLENGES FACING IRRIGATION SECTOR

For those involved in irrigation, the main challenge will be improving water conservation through policy,technological and management interventions. National irrigation agencies, international agencies (includingFAO, CIHEAM, WHO, UNDP, IWMI and EU) and bilateral and multilateral support agencies have importantroles to play in assisting countries meet the challenge successfully. Perhaps the most important areas forwork are:

• proper operation and maintenance of existing systems—with the reduced importance of new construction,it is time to pay special attention to operation and maintenance issues;

• managing water demand through efficient pricing, cost recovery and regulatory measures, and relatededucation and training;

• ensuring widespread user participation—no longer can governments continue to subsidize water and meetall the capital and operating budgetary requirements. Also, the management burden on the public sector istoo heavy. Vigorous efforts to communicate with users on the management and financing of irrigation arenecessary. Related action to improve the reliability of water services is crucial;

• adopting adequate steps to enhance water and land quality measures—environmental assessments, reuse;and related quality control measures—R&D are a necessary part of this task; and

• adopting improved, water-efficient technologies—this is a must if continuing to irrigate also permits thereallocation of water from agriculture to water supply.

WATER-SAVING ASPECTS

The present status of water availability and the foreseeable future shortages fit poorly with the stronglydependent relationship between the production of food and fiber and the availability of controlled water.

Since the total amount allocated to agriculture is so great in comparison to the amounts allocated to urbanand industrial uses, an increase in water use efficiency in the agricultural sector will serve a double purpose.It will free sufficient amounts of water for alternative, industrial uses while, at the same time, it is quitepossible to take away a certain amount without sacrificing food production. Indeed, it is possible to produce“more out of less”.

This water dilemma—to produce more in a sustainable way with less water—poses enormous challengesto reallocate existing supplies, encourages more efficient use and promotes water conservation.

Technical interventions for water saving

Technical interventions to save water could take place at the basin level, the project level and the farm level.Interventions cannot be standardized throughout the region—especially at the basin level—because they

will vary from country to country and from one river basin to another. However, at the basin level, anew storage reservoir could prevent the outflow of flood water to the sea. The construction of link canals


12 A. HAMDY ET AL.

between reservoirs could improve the system operation efficiency and provide optimal mixing of differentquality waters.

At the project level, canal lining or upgrading the technology of water control in the irrigation distributionsystem by moving from one system to another, could save 10–30% of water.

The average conveyance efficiency under traditional open canal systems is around 60%. Conveyance lossesmay be subdivided into: seepage, evaporation, leaks in poorly maintained structures and poor water manage-ment in the distribution network.

Improvement catchment and conveyanceImproved catchment. Losses from evaporation are relatively lower than from seepage. Nonetheless, many

irrigation districts have extensive surfaces exposed to evaporation in natural irrigation ditches or canals withlevees, and evaporation losses can therefore be considerable.

A trend of research which could produce results for reducing evaporation in reservoirs at low cost (ASCE,1974) is the introduction of white floating material. It seems that if albedo is increased, the temperature of abody of water drops and a corresponding reduction in evaporation is thus obtained.

Some methods for reducing evaporation in reservoirs are commercially available, but there are insufficientdata on their performance.

Reduction of seepage in conveyance. Seepage losses occur mainly in natural irrigation ditches andunlined canals in permeable soils. From the point of view of hydraulics, there is no doubt that seepage lossesin unlined ditches are the main cause of water loss during conveyance. The most obvious—but neverthelesscostly solution—is to line channels with masonry or concrete.

Optimization of channel operation. Water management losses occur during distribution and conveyanceand are the result of inadequate operation of the system.

To perform suitable system control is a key point of operation for saving water resources and for supplyingsufficient water into command areas without noticeable delay. The essential points of automatic control are:

• the minimizing of time delay in operation response;• the minimizing of offset value between set discharges and actual discharges;• the stability of response from self-oscillation or deviation; and• maintaining reliability and independence from outside disturbances.

IRRIGATION SUPPLY SYSTEMS

Merriam (1977) stated that “water supplies which are not flexible are the biggest single cause of low efficiency.Farmers must have the ability to turn off the water.” A recognition of this fact is apparent in current trendstoward more flexible water supply systems.

Flexibility means demand-oriented systems that can respond quickly and effectively to farm water require-ments. This has been achieved in several ways, such as canal night storage (e.g. Gezira scheme), automationof canal control gates (e.g. downstream control systems in southern France, North Africa, Near East) andmost recently in the use of pipe systems which respond far more rapidly to changes in demand than do openchannel systems.

Numerous studies have been carried out in this field and applications have been made to the main channelsin major irrigation systems, but it cannot be said that the problem has been solved.

There is need for more economical and reliable methods which can be applied to existing channels (Nayanet al., 1991).



IMPROVED IRRIGATION TECHNIQUES FOR ON-FARM IRRIGATION

The efficiency of on-farm water use can be increased with improved surface irrigation techniques or withsprinkler or micro-irrigation systems.

Micro-irrigation has a great potential to conserve water on the farm (30–50% when compared with surfaceirrigation). Important yield increases per hectare are generally obtained. The potential yield increases percubic meter of water are even more sustainable (often two- or threefold).

Surface irrigation

Innovations which have been already made in surface irrigation were aimed at improving irrigation perfor-mance (efficiency) and its automation (reduction of labour cost). These innovations were centered around theprecision with which land leveling is implemented, and the improvement of the farm water delivery system.Improvement in flexibility has also been demonstrated at farm level by the use of gated pipes. This has beenperhaps one of the simplest and most effective ways of improving flexibility and efficiency of canal watersupplies. Aluminium or PVC pipes up to 300 mm diameter fitted with control valves and field outlets allowfull control over discharges into furrows, borders and even basins.

An innovation development following the introduction of gated pipe has been surge irrigation for furrows.The significance of this technique lies in the simplification it can bring to the management of furrow irri-gation by incorporating management practices into the technology and thus simplifying the work of thefarmer/irrigator. Moreover, surge irrigation has the potential to bring about drastic changes in gravity irriga-tion practices currently in use. It increases efficiency by both reducing drainage losses on the borders of thefarm and ensuring more even application, thus limiting deep percolation losses. Surge irrigation has claimedother advantages. On many soils reductions in soil infiltration rate of one-third to two-thirds have beenreported under surge irrigation when compared to continuous flow, thus encouraging a more rapid advanceand a more uniform application of water.

This new technique merits special attention by researchers and should be evaluated as one of the toppriority research needs. Due to the importance of this technique and its potential for significant improvementin surface irrigation efficiency and water saving, further studies are needed on different ways to model furrowadvance rates, describe the infiltration process and on the method’s practical application and design.

The use of computer-simulated models for the optimal management of surface irrigation systems is one ofthe latest innovations.

A better understanding of the hydraulics of surface irrigation coupled with access to cheap computingtechnology have led to the development and calibration of computer models which can simulate a surfaceirrigation event and thus allow for exploration to rapidly simulate and evaluate scenarios and the impact ofalternative decisions regarding surface irrigation system design and management.

Overhead irrigation

Overhead irrigation has always had a distinct advantage over surface irrigation as a good managementpractice. However, bad design and/or bad management are the two reasons which very often cause poorperformance and efficiency of the sprinkler system. In addition, in developing countries, poor maintenancedue to the lack of skilled people and the availability of spare parts can add greatly to the problem of operation.Unless these difficulties are overcome the basic problems facing sprinkler irrigation may well overshadowcurrent developments which might be considered as mere refinements at wrong end of the system.

Micro-irrigation

Comparing the drip irrigation system with both surface and sprinkler irrigation with respect to water saving,performance (efficiency) management, and operation, cited review and experiences of several countries clearly


14 A. HAMDY ET AL.

demonstrate that this system is more advantageous with respect to the others, particularly for countriessuffering shortages in available water resources.

IRRIGATION TECHNIQUES AND PRE-EXISTING CONSTRAINTS

Despite all the advances, old and inefficient ways still persist throughout many irrigated areas. In too manyplaces, inefficiency is perpetuated by institutionally imposed standards based on excessive and hence wastefulapplications of water. However, institutional inertia and conservative attitudes are only a part of the problem.Some of the new irrigation systems developed in the industrialized countries are indeed too highly mechanized,complex, energy-intensive and large in scale to be directly applicable to the low-capital, low-technologycircumstances of non-highly industrialized countries, where farming is often practised on a small scale andthe relative costs of labour and capital are very different. Hence ready-made modern technology often failswhen introduced arbitrarily into developing countries.

Overall, the best chance for improving the efficiency of water delivery is embodied in a system whichconveys water in closed conduits and that provides measured amounts of water on demand, at a rate calibratedto meet continuous crop needs while preventing waste, salinity and water table rise. Likewise, the mostpromising strategy for improving the efficiency of water utilization appears to be a regime of low-volume,low-pressure, high-frequency, partial-area irrigation applied to suitable crops of high potential yield.

IMPROVED INTERMEDIATE IRRIGATION TECHNOLOGY

Water harvesting

The potential for developing new water supplies by means of water harvesting is tremendous. Though rainfalls infrequently in arid lands, it involves considerable amounts of water; 10 mm of rain equals 100 000 litresof water per ha. Although we will never capture all precipitation, we can certainly collect more than we donow. Rainwater harvesting is possible in areas with as little as 50–80 mm average rainfall.

None of the methods and materials used for water harvesting (land alternation, vegetation management,chemical treatments and ground covers) has been subjected to a long-term economic analysis. Large fieldtrials in different areas are needed to build up a database that could lead to a better understanding of theeconomic viability of different methods in different economic environments. With adaptive research to fit theneeds, economics and materials of developing countries, rainwater harvesting methods may be of exceptionaland immediate value. The major technical research need is to reduce the cost of sealing catchment soils andto make the treatment practical for a wider variety of soils and situations.

Recent technological developments (e.g. special machinery for subsoiling and contour bunding) can accel-erate implementation and at the same time reduce the costs and labour requirements which, in the past,constituted one of the major obstacles to the large-scale adoption of water harvesting.

OTHER APPROACHES FOR WATER SAVING

Since agriculture is by far the main consumer of water in the arid and semi-arid regions, significant watersaving in the agriculture sector could be achieved following other approaches some of which will be outlinedin the following sections.

Reallocation of irrigation water supply to lower water-consuming and high-value crops

Crop rotation is one of the essential factors to be carefully considered for setting a proper irrigation watermanagement demand. Crop patterns should be modified through the use of less water-consuming crops andhigh-value crops to achieve the goal of water saving in the agricultural sector.



In most of the developing countries, irrigation water allocations are heavily influenced by national policiesseeking to achieve food self-sufficiency.

As a result, the current cropping patterns contribute to the consumption of large amounts of water at a timewe are seeking more water saving and economizing the water use in irrigation. Therefore, where croppingpatterns lead to the use of more irrigation water, the cost of water, allocated to crop production measured ineconomic terms, should be considered.

Furthermore, for more efficient water use and better water saving, irrigation scheduling should be verycarefully considered. For irrigation scheduling to be effective, farmers should also be advised on the dischargerate to use and the time of application of such a flow rate (time of cut-off).

In conclusion, in the arid and semi-arid regions, for efficient water use and better water saving in irrigatedagriculture it is necessary to set new strategies for changing cropping patterns to suit to future water allocationbased on the availability of water supply and embark on economic reforms and structural adjustments includingprivate sector development, privatization and trade, price liberalization beside moving towards lifting controlson agricultural crop patterns and shifting towards more profitable crops.

Use of marginal quality water

Limited supplies of fresh water are increasingly in demand for competing uses and create the need to usemarginal quality water in agriculture. From the viewpoint of irrigation, the use of marginal quality waterswill require careful planning, more complex management practices and stringent monitoring procedures thanwhen good quality water is used (FAO, 1992).

Wastewater recycling and use

Generally, speaking, for most arid and semi-arid countries, reuse of wastewater may have greater impact onfuture usable sources of water than any of the technological solutions available for increasing water supply,such as water harvesting, weather modification or desalination. Treated wastewater can be used for irrigation,industrial purposes, groundwater recharge and in special cases, properly treated wastewater could even be usedfor municipal supply. Furthermore, as various industrial and agricultural demands are met by wastewater, morefresh water could be made available for municipal use. In addition, reusing treated wastewater in agriculturecan also be beneficial in that it supplies much of the nitrogen and other nutrients required by agricultural crops.A World Bank study (1992) estimates that the fertilizer value of natural nutrients in wastewater (nitrogen,phosphorus and potassium) is worth about 3 cents m−3 which can save the farmer about $130 ha−1 yr−1

in fertilizer costs; for poor farmers this can be an attractive incentive for the use of treated sewage waterfor irrigation.

Many countries have included wastewater reuse as an important component of water resource planning. Inthe more arid areas in the Mediterranean, wastewater is used in agriculture, thus releasing high-quality watersupplies for potable use. This practice is likely to spread to other arid and semi-arid countries; indeed, aswater scarcity increases, the use of wastewater for irrigation will become obligatory.

If we assume that the total domestic/urban/industrial water supply eventually reaches 125 m3 per personper year, then it is not unreasonable to estimate, based on experience in various countries, that anywherebetween 65 and 80% of the incoming water supply can be recycled and reused. Thus for example, a city witha population of 1 million would require a water supply of 125 million m3 yr−1 and under optimal conditionssome 80% of that amount could be collected in the central sewerage network, treated and recycled for reusein adjacent agricultural areas. In this case some 100 million m3 yr−1 of recycled wastewater might be madeavailable to agricultural areas adjacent to the city.

That amount of water would be sufficient to irrigate between 10 000 and 20 000 ha, depending on theirrigation technology used and the type of crops. If achieved, such recycling and reuse of wastewater canadd significant amounts of water to the agricultural sector. Alternatively, it could be used for higher-valuedindustrial purposes and even for still higher value, urban, non-potable purposes.


16 A. HAMDY ET AL.

To promote wide use of wastewater in agriculture in arid and semi-arid regions a number of issues stillneed to be clarified and appropriate technologies will have to be developed and tested. In this regard, moreemphasis should be given to the following:

• discovering simple, efficient and economical waste treatment methods of low cost systems;• modifying irrigation design, techniques and management to cope with the specific characteristics of the

effluents; and• developing rapid analytical methods for routine monitoring of effluent quality as well as that of irrigation

runoff, drainage and groundwater.

Saline water use

The use of saline water in irrigation is becoming an increasingly important issue in arid regions. It isnecessary to consider this water source within the overall water development and management framework.It should be considered as an additional water source to be properly managed. The sustainable use of thissource will have its beneficial impacts on the water resource through not only increasing the irrigation watersupply, but also to a greater freshwater saving in this field to be directed to other sectoral water uses alreadysuffering water shortages.

Currently, the use of such new sources, particularly in irrigation, has not been properly conceived due toone or more of the following reasons (Hamdy, 1996):

1. lack of national policies and strategies in this area;2. inadequate commitment by decision-makers;3. results are suboptimal due to ad hoc planning and management;4. long-term sustainability is in doubt;5. unnecessarily expensive for the objectives to be achieved;6. major constraints exist in terms of lack of adequate funds for operation and maintenance; inadequate

monitoring and evaluation; lack of trained manpower; and7. health and environmentally related issues are not being properly considered.

The problems undoubtedly are serious, but given proper management and appropriate commitments bydecision-makers, they are surmountable within a limited time period.

Conjunctive use of surface and groundwater resources

The use of saline groundwater in conjunction with fresh surface water is an important means of freshwatersaving and it also helps mitigate waterlogging and salinity hazards.

The conjunctive use can be defined as the development and management of multiple water resources ina coordinated manner such that the total yield of the system over a period of years exceeds the sum of theyields of the individual components of the system resulting from an uncoordinated operation. The objectiveof conjunctive use implies not only the combined use of water resources of more than one type, but also theirexploitation through efficient management in techno-economic terms by taking advantage of the interactionbetween them and the impact of one on the others.

Conjunctive use planning must include principles involved in the two systems independently, but must alsoinclude principles to guide the optimal development of the complementarity of the two systems.

Increasing water productivity

The more we produce with the same amount of water, the less the need for infrastructure development, theless the competition for water, the greater the local food security, and the more water for agriculture, household



and industrial uses and the more that remains in nature. Achieving the greater productivity needed to resolvethe water crisis will not happen automatically—it will require great effort. But it is possible, especially indeveloping countries, where water productivity is far below potential. For cereal grains, for example, therange in water productivity—in biomass produced per cubic meter of evapotranspiration—is between 0.2and 1.5 kg −3. As a rule of thumb, that value should be about 1 kg m−3 (IWMI, 2000). If a country’s demandfor grains grows by 50%, one way to match the increase is to increase water productivity by 50%.

Meeting this challenge will require a far greater effort and significant changes in how water is managed.

HOW CAN WATER PRODUCTIVITY BE IMPROVED IN AGRICULTURE—THE LARGESTWATER USER?

More crop per drop

To increase crop per drop, either production must be increased, keeping water constant, or the same amountof production must be maintained while using less water. There are several ways to achieve this:

• increase the productivity per unit of crop consumption (transpiration);• reduce non-beneficial evaporation or flows to sinks;• reduce pollution;• reduce uncommitted outflows, either through improved management of existing facilities or through devel-

opment of additional facilities;• reallocate water to crops with higher water productivity.

Within each of these broad strategies, more detailed measures can be identified. The choice of strategyfor increasing water productivity will be guided by economic and social factors. Existing water rights willoften constrain choices, especially when there are options of reallocation. In such cases, the basis of waterrights may need to be reconsidered. Local availability of water will be an important consideration dictatingan improvement strategy. In choosing among various strategies, cost-effectiveness is a central consideration.

Most measures to improve water productivity assume that there will be improvements in managementthrough new or restructured organizations.

The following provides details of the key strategic options for increasing crop per drop.

More production per unit transpiration. There are several possibilities to enhance the production perunit transpiration:

• changed crop varieties. Plant breeding plays an important role in developing varieties that yield moremass per unit transpiration. For example, by reducing the growth period while keeping the same yield, theproduction per unit transpiration increases;

• crop substitution. Different crops vary dramatically in their water use, and in their economic returns.Farmers can switch from a more to a less water-consuming crop or switch to a crop with higher economicor physical productivity per unit of water consumed by transpiration;

• deficit, supplemental, or precision irrigation. With sufficient water control, it is possible to achieve moreproductivity per unit of water by irrigation strategies that may not meet full evaporative requirements, butinstead increase returns per unit of transpiration; and

• improved water management. Better timing of water supply, or better timing of the crop cycle, can reducestress at critical crop growth periods, leading to increased yields. By increasing reliability of supply, farmersare motivated to invest more in other agricultural inputs, leading to higher output per unit of water.

Reducing non-beneficial evaporation and flows to sinks. The first task to reduce non-beneficial evap-oration and flows to sinks is to carefully identify these flows, remembering that water diverted primarily foragriculture may serve other beneficial purposes. Reduction of non-beneficial evaporation can be achieved by:


18 A. HAMDY ET AL.

• reducing evaporation from water applied to irrigated fields through irrigation technologies (e.g. drip irri-gation), agronomic practices (e.g. mulching), changing crops or planting dates to match periods of lessevaporative demands;

• controlling evaporation from fallow land, decreasing the area of free water surfaces, decreasing phreato-phytes and controlling weeds; and

• reduction of flows to sinks can be realized by interventions that reduce surface runoff or deep percolationthat flows to sinks like the sea, and is not required for environmental or other commitments.

Pollution control. Controlling pollution can increase the amount of water available for reuse by:

• reducing flows through saline soils or through saline groundwater to reduce mobilization of salts intoirrigation return flows;

• shunting saline or otherwise polluted water directly to a sink and avoiding the need to dilute it with freshwater;

• utilizing a basin-wide irrigation strategy that controls reuse of return flows;• reducing pollution entering irrigation water supplies through return flows of municipal and industrial

users; and• reducing pollutants originating from rainfed and irrigated agriculture.

Using not yet committed flows. Even with present levels of infrastructure development, there is muchoutflow beyond downstream commitments that could be tapped. This can be done by:

• improved management of existing facilities to obtain more beneficial use from existing water supplies;• adding storage facilities and releasing water during drier periods. The storage could take many forms

besides impoundment behind reservoirs, including storage in groundwater, and storage in small reservoirsand in ponds on farmers’ fields; and

• reusing return flows to increase irrigated area.

Reallocating water between uses. Reallocation of water from lower- to higher-value uses (from agri-culture to municipal and industrial uses or from low- to higher-value crops) affects downstream availability.Such reallocation can have serious legal, equity and other social considerations that must be addressed.

Plan of action

To help avert the water crisis and alleviate the problems due to shortages in available water resources indeveloping and developed countries, an outline of the Plan of Action is suggested, which would have twolevels of initiatives:

• at the country level, and• at the international level.

The First —initiatives at the country level. They may include:

1. Efficient use of scarce water and monitoring and reduction in pollution through:• irrigation efficiency;• demand management;• sustainable groundwater use;• improving water quality;• use of high technology in irrigation application.

2. Alternative sources of water supplementation—initiatives may include:• evaluation and identification of supplementation of existing supply with alternate resources like desali-

nation;



• reuse of non-conventional water.3. Integrating water resources management through:

• promotion of conservation and improvement in sectoral allotments;• investigation of resource utilization and water audits;• institutional support;• preparation of a national water conservation strategy including water law and water pricing;• preparation of plans for decentralization and turnover.

4. Mobilizing country effort by:• public awareness campaigns;• local participation;• involvement of water user associations;• promoting NGO forums for a two-way communication between the government and the community.

The Second: —initiatives at regional and international levels. These may include:• capacity building through international cooperation;• transfer of latest technology in the water sector;• liaison with donors;• organization of workshops for international experience sharing;• cooperation with other water-related organizations like Global Water partnership and the World Water

Council;• development of the data and institutional research network through IPTRID, IWMI, CIHEAM and other

research institutions.

This outline plan only proposes key areas. It is unlikely that a “blueprint” approach can devise a strategyfor water conservation under varied conditions since country requirements are different and each countryshould set its own target. This requires a concerted and sustained effort with set objectives and clearlydefinable targets.

However, the successful implementation of such proposed plan of action to attain major benefits fromhigher efficiency in irrigation sector, the efforts should be directed towards:

• development of human resources;• improvement of institutional capacities;• establishment of an efficient technical assistance capable to implement the new techniques required as well

as friendly working with the users (farmers); and• gathering the scattered information in the region and creating wide links of cooperation not only among the

scientific institutions but also between researchers and scientists in the region. Networking and establishmentof national and regional networks in the appropriate approach to be followed.

REFERENCES

Alcamo J, Henrichs T, Rosch T. 1999. World Water in 2025: Global Modeling and Scenario Analysis for the World Commission onWater for the 21st Century. University of Kassel, Center for Environmental System Research, Germany.

Alcamo J, Doll P, Kaspar F, Siebert S. 1997. An overview of the global freshwater situation. Expertise for WBGU. Mimeo.ASCE. 1974. Water management through irrigation and drainage progress, problems and opportunities. Committee on research of

irrigation and drainage division, ASCE, IR2.Clarke D. 1993. Water: the International Crisis. Cambridge University Press: Cambridge.Cosgrove JW, Rijsberman RF. 2000. World Water Vision. World Water Council, Earthscan UK.FAO. 1992. Wastewater treatment and use in agriculture. Pescod, M.B. (ed.). Irrigation and Drainage Paper 47, Rome.FAO. 1996. Food summit. Technical background documents. Rome, Italy.Hamdy A. 1996. Use and management of saline water for irrigation towards sustainable development. In Sustainability of irrigated

agriculture. NATO ASI Series, Applie Sciences, vol. 312, Pereira LS, Feeds RA, Gilly JR, Lesaffre B. (eds); 359–372.Hamdy A, Lacirignola C. 1999. Mediterranean Water Resources: Major Challenges towards the 21st Century. Mediterranean Agronomic

Institute of Bari, Italy.IWMI (International Water Management Institute). 2000. Water Supply and Demand in 2025. Colombo, Sri Lanka.


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Merrian JL. 1977. Efficient Irrigation. California Polytechnic State University, San Louis Obispo, California.Nayan S, Pandy AD, Debajyoti C. 1991. Feasibility for canal automation to an existing canal: a case study. Proceedings of the

International Seminar of Efficiency Water Use, Mexico. Oct. 21–25.Rosegrant MW, Ringler C. 1999. World Water Vision Scenarios. Consequences for Food Supply, Demand, Trade and Food Security.

Results from Impact Implementation of the World Water Vision Scenarios. International Food Policy Research Institute: Washington,DC.

Seckler DU, Amarasinghe U, Molden D, Da Silva R, Barker R. 1998. World Water Demand and Supply, 1990 to 2025. Scenarios andIssues. Research report 19. IWMI: Colombia, Sri Lanka.

Shiklomanov IA. 1999. World Water Resources and Water Use: Present Assessment and Outlook for 2025. State Hydrological Institute,St. Petersburg, Russia.

World Bank. 1992. World Bank Development Report. Oxford: New York.World Water Forum. WWCouncil. 2000. A Vision of Water for Food and Rural Development. World Water Forum. 17 March. The

Hague, The Netherlands.WRI. 1994. A Guide to the Global Environment. Oxford University Press: New York, Oxford.WRI. 1996. World Resources 1996: The Urban Environment. Oxford University Press: New York, Oxford.WWI (World Watch Institute). 1996. World Watch Data-base Disk. Frankfurt: Umwelt Kommunikation.


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