FIGURE 2-1 Regional irrigation water application for various crops for six regions of the United States. Irrigation application is normalized by area, and is in feet.

SOURCE: N.Gollehon, U.S. Department of Agriculture (USDA) Economic Research Service (ERS), written commun., July 12, 2007. Based on data from USDA Census of Agriculture.

different type of biomass will result in increased water use in some cases, in other cases a decrease.

As an example, in much of the country, the crop substitution is from soy to corn. The regional effects of this can be seen in Figure 2-1. Corn generally uses less water than soybeans and cotton in the Pacific and Mountain regions. The reverse is true in the Northern and Southern Plains, and the crops use about the same amount of water in the North Central and Eastern regions. Changes in agricultural water use would generally parallel these trends. Another example is in Northern Texas, where annual evapotranspiration (ET) rates per year for alfalfa, corn, cotton, and sorghum are estimated to be about 1,600, 760, 640, and 580 mm (63, 30, 25, and 23 inches), respectively. Therefore, regional water loss to ET will likely decrease if