Geohydrology of the High Plains Aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming

The High Plains aquifer, which underlies about 174,000 square miles in parts of eight States, is the principal source of water in one of the Nation's major agricultural areas. About 170,000 wells pump water from the aquifer to irrigate about 13 million acres in the High Plains. In 1978, the U.S. Geological Survey began a regional study of the High Plains aquifer to provide geohydrologic data and computer models of the aquifer needed to evaluate the effects of ground-water development. This report describes the geohydrology of the High Plains aquifer.