The pairing of irrigation and h y d r o p o w e r in a discussion of progress in the hydrospheric sciences may seem an incongruity. In many ways the use o f water for irrigation or for the generation of electric power is in conflict, the first requiring seasonal use only and the latter a steady supply year around with only daily fluctuations to meet demands. Initially, the water resource projects were single purpose, built and operated to provide irrigation or to generate power.

However, to make efficient use of water, both require water control structures involving the same basic scientific principles. Also, in areas of limited water supply, such as the western half of the United States, it soon became evident that water development projects must be multipurpose for the best overall returns. The pioneering work in the application of science to large-scale water control for irrigation and power generation has largely taken place in the large multipurpose water development programs of the West.