Change in Water in Storage in the High Plains Aquifer, Predevelopment to 2013

Abstract:

The High Plains aquifer underlies about 175,000 square miles in parts of eight States—Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. The aquifer is the principal source of water for irrigation and public supply in this area, which is one of the major agricultural areas in the United States. However, soon after groundwater irrigation began, water-level declines occurred in some parts of the aquifer. In response, the U.S. Geological Survey, in cooperation with numerous Federal, State, and local water-resource agencies, began monitoring groundwater levels in the aquifer. Water levels are measured annually primarily in irrigation wells in winter to early spring (generally January to May, depending on location), when water levels generally have recovered from groundwater pumping for irrigation in the previous growing season and before the current year’s irrigation season. The water-level elevation for predevelopment (about 1950) conditions was determined using water-level measurements from more than 20,000 wells. The water-level elevation for 2013 was measured in more than 9,000 wells. The water-level measurements were analyzed and interpolated to map discrete intervals of water-level changes from predevelopment to the year 2013. The change in the volume of drainable water stored in the aquifer was calculated using the mapped area of each water-level-change interval, the average water-level change within each mapped interval, and the estimated average specific yield for the aquifer.