Water and Development: The Importance of Irrigation in Developing CountriesBy Karina Schoengold and David Zilberman1. Overview2. The Benefits and Cost of Irrigation2.1. BENEFITS OF IRRIGATION2.1.1. Contribution of Irrigation to Agricultural Productivity2.1.2. Food Supply ExpansionIrrigation and agricultural land expansionIrrigation and increased crop yieldsIrrigation and double cropping of land2.1.3. Welfare ImprovementsIrrigation and employment opportunitiesIrrigation and land values2.1.4. Irrigation Supply Stabilization2.1.5. Environmental BenefitsIrrigation and deforestation22.1.6. Benefits of the Conjunctive Use of Groundwater and Surface Water2.2. COSTS OF IRRIGATION2.2.1. Capital Costs2.2.2. Environmental CostsHabitat destructionBlocking migration of native speciesIncreased emissions of greenhouse gases.2.2.3. Dynamic Cost on Water ResourcesIncreased salinity levels in freshwater suppliesWaterlogging and salinization of landDecreased levels of sediment and nutrients in waterContamination of water supplies2.2.4. Social ConcernsWaterborne diseasesDisplacement of native populationsInternational conflicts and water supply2.2.5. Overuse of Groundwater Resources2.2.6. Environmental Problems Associated with the Overdraft of Groundwater3. Actions to Improve Efficiency of Irrigation33.1. EFFICIENT INVESTMENT IN IRRIGATION PROJECTS3.1.1. The Basic Economics of Oversized Water Projects3.1.2. Dynamic Consideration and Uncertainty3.1.3. Waterlogging and Drainage3.1.4. Use of Non-Traditional Water Sources3.1.5. Trade and the Concept of “Virtual Water”3.2. IMPROVED CONVEYANCE AND THE ALLOCATION OF WATER.3.2.1. Management of Conveyance System3.2.2. Transition from Water Rights to Water MarketsWater rights systemsThe transition to trading and markets3.2.3. Improved Efficiency of Water Pricing SystemsInaccurate volumetric measurementSubsidization of water delivery costs3.2.4. Improved Efficiency of Groundwater ManagementGroundwater as an open-access resourceSubsidization of groundwater pumping costsIntroduction of efficient groundwater pricing43.3. INEFFICIENCIES IN MICRO-LEVEL WATER MANAGEMENT3.3.1. Land Allocation to Irrigation at the Farm Level3.3.2. Irrigation Choice at the Farm Level3.3.3. Existence of Low-Capital Efficient Irrigation Technologies4. ConclusionAppendix 1Appendix 2ReferencesWater and Development: The Importance of Irrigation in Developing CountriesBy Karina Schoengold and David ZilbermanThe post-World War II era has witnessed a drastic increase in irrigation activities that havecontributed substantially to the massive growth in agricultural production that enables humanityto feed its doubling population. However, a distinction has to be made between the overallpositive contribution of irrigation and water to agricultural productivity and economic welfareand a significant amount of misallocation and management of resources that have accompaniedthe expansion of irrigation. In many cases, water resources have been overdeveloped; there hasbeen overspending on capital; and significant cost in terms of loss of ecosystems, extinction offish species, and contamination of water sources. This chapter provides an economic perspectiveon the contribution or irrigation and water resources to the post-WW II agricultural developmentand provides a perspective for agricultural water resource management and policies in the future. First, we will have an overview of the benefits and costs of agricultural water andirrigation projects in developing countries. There is a paucity of ex post integrated assessmentsof these projects, so we can put the pieces together, combing data with conceptual arguments.The second part of the chapter consists of three sections that present an economic framework fordesigning water institutions and policies in the future to improve water resource allocation andprevent some of the inefficiency in water resource systems at the present. The third part of thechapter ventures beyond irrigation and addresses impacts of agriculture on water quality andhuman and environmental health and presents mechanisms to address these impacts.21. OverviewThe last century has seen unprecedented growth in irrigation projects on a global level. The useof tube well irrigation has decreased the cost of using groundwater, and the subsidization of largereservoirs and canals has been used to achieve food security. Worldwide, irrigated land hasincreased from 50 mha (million hectares) in 1900 to 267 mha today (Gleick, 2000). Much of thisincrease has been in developing countries. Between 1962 and 1996, the irrigated area indeveloping countries increased at about 2 percent a year, leading to a near doubling in irrigatedland. For example, in 1950 India had an irrigation potential of 22.6 mha. By 1993-94, this hadgrown to 86 mha (Saleth, 1996). Between 1949 and 1998, the amount of land in China underirrigation increased from 16 mha to 52.3 mha. This represented a change from 16% to 40% ofChina’s total farmland (Guangzhi, Yuansheng, and Hansong, 1999). Currently 75 percent of allirrigated land is in developing countries. Irrigation has increased the amount of land undercultivation, and the yields on existing cropland. It has also allowed double cropping, and hasdecreased the uncertainty of water supplied by rainfall.Despite all of these benefits, there have also been substantial costs as a result of theconstruction of water projects and the growth in cropland. These have been costs in the form ofcapital, environmental degradation, and diminished human health. In many areas there has beenthe destruction of native habitats, the displacement of indigenous people, soil erosion, a decreasein water quality, and an increase in waterborne diseases, just to name a few of the problems thatresult either directly or indirectly from the growth in irrigated lands. Globally there is a lot ofheterogeneity among land qualities and populations. Not every location is well suited to waterdevelopment, and the potential benefits of irrigation have not been spread evenly throughout theworld. The following chart shows the distribution of irrigation dams built throughout the world.3There have been many irrigation projects developed in Asia, which have been mostly successful.South America and Africa have had relatively few irrigation projects developed, and the benefitshave been minimal.An important concern for the future is the limited supply of fresh water.
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