Book excerpt: Irrigation has long played a key role in feeding expanding populations and is expected to play a still greater role in the future. However, is it sustainable? Can it remain in existence and function continuously and indefinitely? Some pessimists doubt that it is. This volume presents a more positive approach with carefully conditional optimism. It takes the diffuse, voluminous and disparate facts and combines them in a unified exposition. It merges physico-chemical, agronomic, environmental and economic principles into practical recommendations to help ensure the long-term viability and productivity of irrigated agriculture in arid and semiarid regions.