The general availability of ground water was determined from well records collected by the U.S. Geological Survey and cooperating State, local, and Federal agencies. Data are for aquifers that in most places are less than 1,000 feet below the land surface. In areas of few or no wells, potential well yields are inferred from geologic data. Special investigations are needed to determine specific factors such as depths and sustained yields of aquifers, water levels, and suitability of water for use in any given area. More detailed information about principal aquifers for specific parts of the map area are obtainable from the district office of the Water Resources Division, U.S. Geological Survey, Salt Lake City, Utah.