6.9 HIGH PLAINS AQUIFER
The High Plains aquifer is an extensive regional aquifer that underlies approximately 174,000 square miles of the Great Plains states extending from South Dakota on the north to Texas and New Mexico on the south (Figure 6.9-1). The aquifer is of significant economic importance as it provides ground water to approximately 20 percent of the irrigated cropland in the United States.
Figure 6.9-1 Location and extent of the High Plains aquifer from a regional perspective. From Cederstrand and Becker, 1998a.
In Colorado, the High Plains aquifer is present beneath all or parts of Weld, Logan, Sedgwick, Phillips, Washington, Yuma, Lincoln, Kit Carson, Cheyenne, Kiowa, Prowers, Las Animas, and Baca counties (Figure 6.9-2). Land use in eastern Colorado is almost exclusively agricultural with most ground-water withdrawal used for irrigation and crop-related purposes. The topography is characterized by flat to gently rolling terrain that is bisected by mostly eastward-flowing rivers and streams.
The population in eastern Colorado remains low, with population densities rarely exceeding four to nine residents per square mile. Colorado counties containing the High Plains aquifer are included in the Office of the State Engineer Water Divisions 1 and 2. Most of the aquifer is a part of Colorado’s Northern or Southern High Plains Designated Ground-Water Basins and their associated ground-water management districts. Virtually thousands of wells (15,600 wells of record as of February 2001) are completed in the High Plains aquifer, as depicted in Figure 6.9-2.