The High Plains aquifer in Kansas is a part of a regional system that extends from South Dakota to Texas. The aquifer in Kansas underlies an area of 31,000 square miles in the western and south-central part of the State. This aquifer is a hydraulically connected assemblage of unconsolidated water-bearing deposits of Tertiary and Quaternary age. Maps published at a scale of 1:500 ,000 show the altitude and configuration of the water table in Kansas during 1980. Ground water moves from higher altitudes in the western part of the high Plains to lower altitudes in the eastern part at an average rate of 10 feet per mile. The up-gradient flexure of water-table contours along some of the valleys indicates that ground water discharges to the streams in those areas. (USGS)