In most States, consumptive use was based on coefficients ranging from 40 to 100 percent of withdrawals, or on theoretical crop requirements. In a few States, consumptive use was calculated as the difference between reported withdrawals and reported return flows. Irrigation withdrawals as well as acres irrigated during 1990 were about the same as during 1985. Irrigation use represents 40 percent of total freshwater use for all offstream categories. Surface water was the source for about 63 percent of irrigation withdrawals, and, except for a small fraction of 1 percent that was reclaimed wastewater, ground water furnished the remainder.
Irrigation is by far the largest water use in the West.
Florida withdrew the most water for irrigation in the East although it ranked thirteenth nationwide.