The use of water for agricultural purposes is the largest consumptive use of water in the United States, even though in recent years withdrawals of water for industrial purposes exceed those for irrigation. Generally, over half of the water withdrawn for irrigation is consumed by evaporation and transpiration, while less than a tenth of the water withdrawn for industrial purposes is consumed. Therefore, in view of the increasing trend to irrigation in the humid areas of the country as a means of increasing crop yields, irrigated agriculture may well be significant. The Department of Agriculture has considered the land and water potentials of the United States and made projections of future requirements for low, medium, and high levels of population in 1980 and 2000, with estimates of how these requirements may be divided among the several water resource regions into which the committee staff has divided the United States for the purpose of analyzing future water needs.