Water scarcity driven by climate change, growing demand, and inefficient management of water and related infrastructure is a serious threat to livelihoods in the Aral Sea Basin (ASB) of Central Asia. In recent decades, downstream water shortages have become increasingly common and inflows into the Aral Sea have become very limited. Meanwhile, water losses are enormous both at conveyance and field levels because of outdated infrastructure and the dominance of highly inefficient basin and furrow irrigation methods. Intensification and modernization of irrigation systems, while requiring investment of scarce capital resources, could thus substantially reduce non-beneficial water consumption and help in coping with increasing water scarcity. This study applies a hydro-economic model that solves for the investment in improved irrigation efficiency across the various irrigation sites in the ASB that delivers the highest economic gains. Improvement of the efficiency of irrigation canals and implementation of field efficiency investments and practices, such as drip irrigation, and alternate dry or short furrow irrigation (for rice), would substantially improve economic outcomes. Conveyance efficiency investments are particularly worthwhile in downstream regions where sandy soils are common and return flows largely feed saline lakes in tail-end depressions. Meanwhile, field-level efficiency should be fully upgraded in all rice-producing regions through the use of drip and alternate wet and dry irrigation, as well as with drip irrigation in the cotton-producing Ferghana Valley of the Syr Darya Basin. The value of these improvements increases with reduced water availability. Implementation of an optimal set of investments could increase basinwide benefits by 20% (from US$ 3.2 to 3.8 billion) under normal water availability and by 40% (from US$ 2.5 to 3.5 billion) under dry conditions (80% of normal supply).
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