Changes in ground-water levels in selected wells in the Arkansas River alluvial aquifer downstream from Pueblo Reservoir, southeastern Colorado, 1965-2001

Abstract

The Arkansas River alluvial aquifer of Quaternary age underlies the Arkansas River in southeastern Colorado (fig. 1). The aquifer is 1 to 6 miles wide and extends about 150 miles from Pueblo County through Otero, Crowley, Bent, and Prowers Counties to the Colorado-Kansas State line (figs. 6-9). The aquifer is hydraulically connected to the Arkansas River and is underlain by relatively impermeable bedrock of Cretaceous age. The aquifer is as much as 200 feet thick and consists of unconsolidated clay, silt, sand, and gravel. Depth to water generally is less than 60 feet below land surface (Voegeli and Hershey, 1965; Weist, 1965; Lohman and others, 1974). The U.S. Geological Survey (USGS) has measured water levels in wells completed in the Arkansas River alluvial aquifer since about 1965 for various programs. Currently (2002) the USGS measures water levels during the spring and fall of each year in 35 wells in the aquifer, in cooperation with the Southeastern Colorado Water Conservancy District (SECWCD) (figs. 6-9). Long-term, systematic water-level measurements are needed to monitor stresses on the aquifer that affect recharge and ground-U.