This raster data set represents water-level change in the High Plains aquifer of the United States from 1980 to 1995, in feet. The High Plains aquifer underlies 112.6 million acres (176,000 square miles) in parts of eight States: Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming. The aquifer's saturated thickness ranges from near zero to about 1,200 feet (Weeks and Gutentag, 1981). Water-level declines occurred in parts of the High Plains aquifer soon after the onset of substantial irrigation with groundwater (about 1950) (Luckey and others, 1981; Gutentag and others, 1984). This data set was generated in ESRI ArcInfo Workstation Version 9.3, which is a geographic information system (GIS), using water-level-change data from wells measured in 1980 and 1995 and from some additional wells in New Mexico, which were measured in 1996 and 1997. For this data set, areas of no substantial change were designated as areas where water-level change was between a rise of 3 feet and and decline of 3 feet; the raster was set to zero in the areas of no substantial change. REFERENCES CITED -- Gutentag, E.D., Heimes, F.J., Krothe, N.C., Luckey, R.R., and Weeks, J.B., 1984, Geohydrology of the High Plains aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Professional Paper 1400-B, 63 p. Luckey, R.R., Gutentag, E.D., and Weeks, J.B., 1981, Water-level and saturated-thickness changes, predevelopment to 1980, in the High Plains aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Hydrologic Investigations Atlas HA-652, 2 sheets, scale 1:2,500,000. Weeks, J.B., and Gutentag, E.D., 1981, Bedrock geology, altitude of base, and 1980 saturated thickness of the High Plains aquifer in parts of Colorado, Kansas, Nebraska, New Mexico, Oklahoma, South Dakota, Texas, and Wyoming: U.S. Geological Survey Hydrologic Investigations Atlas HA-648, 2 sheets, scale 1:2,500,000.