High Plains Aquifer
ü The High Plains is a 174,000-square-mile area of flat to gently rolling terrain that includes parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming.
ü The area is characterized by moderate precipitation but generally has a low natural recharge rate to the ground-water system.
ü Unconsolidated alluvial deposits that form a water-table aquifer called the High Plains aquifer (consisting largely of the Ogallala aquifer) underlie the region.
ü Irrigation water pumped from the aquifer has made the High Plains one of the Nation's most important agricultural areas.
ü During the late 1800's, settlers and speculators moved to the plains, and farming became the major activity in the area.
ü The drought of the 1930's gave rise to the use of irrigation and improved farming practices in the High Plains (Gutentag and others, 1984).
ü Around 1940, a rapid expansion in the use of ground water for irrigation began. In 1949, about 480 million cubic feet per day of ground water was used for irrigation.
ü By 1980, the use had more than quadrupled to about 2,150 million cubic feet per day (U.S. Geological Survey, 1984).
ü Subsequently, it declined to about 1,870 million cubic feet per day in 1990 (McGuire and Sharpe, 1997).
ü Not all of the water pumped for irrigation is consumed as evapotranspiration by crops; some seeps back into the ground and recharges the aquifer.
ü Nevertheless, this intense use of ground water has caused major water-level declines and decreased the saturated thickness of the aquifer significantly in some areas
ü These changes are particularly evident in the central and southern parts of the High Plains.