The Ogallala Aquifer is an extensive underground reservoir that supplies water to most of the irrigated agriculture in the central United States. Discovered early in the nineteenth century, this aquifer—also known as the High Plains regional aquifer—became a major economic resource in the 1960s and 1970s when advanced pumping technology made large-scale irrigation possible. In 1980 this aquifer supported 170,000 wells and provided one third of all irrigation water pumped in the United States. In the last several decades, Ogallala-irrigated agriculture has redefined the landscape of the central United States by fostering economic expansion, population growth, and the development of large-scale agribusiness in an arid region.

The High Plains regional aquifer underlies eight states, including most of Nebraska and portions of South Dakota, Wyoming, Colorado, Kansas, Oklahoma, Texas, and New Mexico. Covering an area of 175,000 square miles (453,250 sq km), the aquifer runs 800 miles (1,288 km) from north...