This report includes two maps of the same location, one describing water-level contour, well depth in which depth to water was measured, the other describing well from which water sample was collected and irrigated areas. It includes a letter from the district chief of the United States Department of the Interior to users of the geological survey hydrologic data.

Scope: This report summarizes part of the hydrologic data needed to determine the effects of streamflow on ground-water storage. The report includes (1) streamflow data at selected points between the water-conservation reservoirs on the Salt and Verde Rivers and the Gila River as Gillespie Dam, (2) changes in ground-water levels in 169 observation wells from February 1978 to May 1980, (3) an estimate of the streamflow losses along the Salt and Gila Rivers between Granite Reef and Gillespie Dams from March 1978 to June 1980, and (4) the infiltration rates on May, 9, 1979, for the Salt River downstream from Granite Reef Dam. Most of the hydrologic data in this report are available in computer-printout form and may be consulted at U.S. Geological Survey offices in: Federal Building, 301 West Congress Street, Tucson, and Valley Center, Suite 1880, Phoenix. Copies of the data can be obtained at private expense.

Map and survey information of the the Aravaipa Valley area in Arizona, including information on well depths, irrigated areas, approximate boundaries, and arbitrary boundaries of ground-water area, as well as general hydrologic data and selected references.

Purpose and scope: The purpose of this study was to develop a method for estimating the amount of subsurface return flow to the Colorado River in the Yuma area. This report presents a method that will permit an accounting of ground-water return flows from each side of the Colorado River in the Yuma reach. The estimates of return flow can be used by water-management agencies in determining return-flow credits for the States of Arizona and California.

Purpose and scope: The purpose of this study was to develop a method for estimating the amount of subsurface return flow to the Colorado River in the Yuma area. This report presents a method that permits an approximate accounting of ground-water return flow from each side of the Colorado River in Yuma reach. The method presented in this report was developed specifically for application in the Yuma area. The validity of the assumptions inherent in the method was evaluated on the basis of the local hydrologic system. The applicability of the method to other hydrologic systems is not addressed in this report.

Abstract: Water shortages are expected in the Upper Colorado River Basin because of increasing water demands for various uses. Ground-water supplies can help to reduce water shortages but ground-water reservoirs have not been studied in detail. The regional aquifer systems analysis of the Upper Colorado River Basin is a study of the major ground-water resources of the region. Aquifers occur in the sedimentary rock sequences in basins and uplifted regions, in volcanic-rock regions, and in stream-valley alluvium. The project work will include collection and compilation of existing geologic, geophysical, hydrologic, and geochemical data. These data will be used to assess the hydrologic characteristics of the aquifer systems and to estimate the hydrologic effects of discharge from, or recharge to, selected aquifers.