Continuing studies are being made in west-central Kansas to provide up-to-date information to aid in the management of groundwater for irrigation. This report, prepared in cooperation with the Western Kansas Groundwater Management District No. 1, presents the fifth in a series of studies that uses a statistical technique, called kriging, to produce hydrologic maps that are used as management tools.

Kriging is a statistical technique that was used to interpolate water level altitudes at the center of each 1-square-mile section in the study area based on measured water levels at 165 observation wells. These interpolation altitudes (1,859 in all), along with bedrock surface and base year water table altitudes, were used to prepare a geohydrologic map illustrating percentage change in saturated thickness. Saturated thickness, as used in this report, is the thickness of the High Plains aquifer between the groundwater surface indicated by water table altitudes and the bedrock surface. Because irrigation development in west-central Kansas was minimal prior to 1950, the saturated thickness during 1950 represented a nearly static condition in the aquifer. Thus, the effects of irrigation withdrawalson the volume of water in storage could be related to the decrease or percentage change in saturated thickness of the aquifer from 1950 to average saturated thickness during 1983-85.