Prince William Forest Park is in the southern part of Prince William County, Va. Its natural beauty and nearness to Washington, D.C. have made it one of the most popular recreation areas in northern Virginia. To help the National Park Service plan the development of new facilities and effectively manage its total resources, the U.S. Geological Survey made a hydrologic study of the park from October 1972 to November 1975. The overall objective of the Survey 's study was to evalute the quantity and quality of the park 's water resources. Available information was compiled and analyzed, and new data on streamflow, ground-water levels, and the chemical quality of water were collected. Test wells were drilled and aquifer tests made at the sites of wells to evaluate the occurrence and availability of ground water. (USGS)