The purpose of this investigation was to correlate the results of past studies in parts of five developed basins in southwestern Utah and to give a unified concept of ground-water conditions in the entire area. The area of investigation comprises about 3,600 square miles in Washington, Iron, Beaver, and Millard Counties, including the five developed basins - Beaver, Cedar City, and Parowan Valleys and the Milford and Beryl-Enterprise districts in Escalante Valley. Annual precipitation in the area ranges from less than 8 inches in parts of the valleys to more than 30 inches in the mountains to the east, with most of the precipitation falling during the October-April period.