Preliminary maps showing ground-water resources in the Lower Colorado River region, Arizona, Nevada, New Mexico, and Utah

This atlas was prepared to meet the need for information on the areal distribution, quantity, and availability of ground water in the lower Colorado River region, an area of about 140,000 square miles in parts of Arizona, Nevada, New Mexico, and Utah. The maps are necessarily generalized in places owing to the lack of sufficient data. In general the geohydrologic information pertains to large areas, and local exceptions occur. Users needing more detailed information for specific areas may address inquiries to the district chief of the U.S. Geological Survey at the addresses given in the section “Selected References.” The maps were prepared using data from previously published reports, data collected by other Federal State, and local agencies, and data from the files of the U.S. Geological Survey offices in Arizona, Nevada, New Mexico, and Utah. The report is the result of the lower Colorado River region Type I framework study made in cooperation with the U.S. Bureau of Reclamation.