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, (HA-648): Weeks, John B. Gutentag, E. D., Weeks, J. B. (1:2,500,000; 1981), two color sheets, size 48" x 28". Description: This report describes the bedrock geology, altitude of base, and saturated-thickness of the High Plains Aquifer. Out of print, reprinted map available.