Southwestern Kansas is one of the principal areas of ground-water development for irrigation in the State, and many reports are available concerning ground-water conditions in the area. The purposes of this investigation were to consolidate and update data, to determine the extent and effects of irrigation development on the ground-water resource, to determine the chemical quality of the ground water in relation to irrigation use, to describe the general operation of the hydrologic system, and to identify problem areas where intensive quantitative studies will be needed by State and local agencies for planning and management of the resource. This study began in 1972 as part of a cooperative program of ground-water investigations between the Kansas Geological Survey and the U.S. Geological Survey. Support in this study was provided by the Division of Water Resources of the Kansas State Board of Agriculture and the Division of Environment of the Kansas Department of Health and Environment.