U.S. Irrigation. Extent and Economic Importance. Agriculture Information Bulletin Number 523.

Data for the years 1974, 1978, 1982, and 1984 are used to identify the principal features of irrigated farming in the United States and to assess the importance of irrigation to the farm economy. Irrigation of U.S. acreage declined 5.6 million acres between 1978 and 1984 to 44.7 million acres. In 1982 irrigated acreage represented 6 percent of the 820 million acres of cropland and pastureland harvested in the contiguous United States. These irrigated lands accounted for about 13 percent of all cropland harvested in 1982, however, and thus contributed 32 percent of the total value of the crops produced that year. Irrigation was used on the entire rice crop; 60 to 70 percent of vegetable, potato, and orchard crops; 53 percent of the sugar beet crop; and 35 percent of the cotton crop. Other crops were irrigated in proportions ranging from 4 to 17 percent. The four western regions (Northern Plains, Southern Plains, the Rocky Mountain, and Pacific areas) accounted for almost 85 percent of all irrigated land. The most rapid increase in the use of irrigation occurred in the Lake States and Corn Belt, where irrigated acreage nearly doubled between 1974 and 1982. Other areas in which the use of irrigation was increasing at a rapid rate included Appalachia (67 percent), the Southeast (73 percent), the Delta States (78 percent), and the Northern Great Plains (52 percent). Irrigation declined 14 percent in the Southern Plains. As of 1984, about 60 percent of all irrigation systems were gravity flow systems, with the remainder being either sprinkler or drip systems. (MN)