ANALYSIS OF LONG-TERM WATER-LEVEL CHANGES IN THE OKLAHOMA PANHANDLE REGION OF THE OGALLALA AQUIFER

The Ogallala aquifer underlies a major agricultural region in the central United States and has been extensively used for irrigation since the 1930’s. The portion of the Ogallala Formation that underlies the Oklahoma Panhandle is defined by the Oklahoma Water Resources Board as a major aquifer called the Ogallala-Panhandle aquifer and has reported water use four to five times higher than any other aquifer in Oklahoma. Utilizing long-term groundwater-monitoring data from winter months between 1982 and 2022 in wells in Oklahoma and adjacent counties in Texas, Kansas, and Colorado, groundwater-level change maps were created and local water-level declines of over 100 feet were observed in portions of the Oklahoma-Panhandle aquifer. The mean observed water-level decline within measured wells in the Ogallala-Panhandle aquifer from 1982-2022 was 28.6 feet, and the mean raster-interpolated water-level decline was 15.7 feet. Most areas without observed water-level decline in the Ogallala-Panhandle aquifer have minimal saturated thickness or are in areas where the Ogallala Formation deposits have been mostly eroded. The portions of the Ogallala-Panhandle aquifer with the largest groundwater declines were in north-central and southwest Texas County, areas which also have the highest density of water-use permits in the Oklahoma Panhandle. Splitting the 40-year interval of 1982-2022 into two 20-year intervals, 1982-2002 and 2002-2022, an acceleration in water-level decline over the last 20 years is observed, suggesting long-term groundwater availability could be a continuing concern for the region.