Abstract
Only about 3% of the world's total water supply is fresh, and most of this (87%) is locked up in ice caps or glaciers, in the atmosphere or soil, or deep underground. Mankind's primary supply of freshwater is the renewable component (precipitation minus evapotranspiration) which flows through aquifers, streams and lakes. An estimated 3,240 cubic kilometers of fresh water are withdrawn annually. About 70% is for agriculture, mainly for irrigation. Although agriculture accounts for a large share of world water use, providing adequate water in a timely and reliable manner to irrigate crops is a formidable challenge in most parts of the developing world. It will be even more challenging over the next few decades. This paper examines some significant issues that the world must address in the remaining years of this century to ensure that irrigated agriculture achieves its potential.
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