William G. Wilber P. Patrick Leahy 1991 The concepts that are the basis for the U.S. Geological Survey's National Water-Quality Assessment (NAWQA) program began forming in the early 1980's. By 1986, a pilot phase was initiated to test and refine assessment concepts and in 1991, the NAWQA program began a multi-year transition to a fully operational program. The goals of the program are to describe the status and trends in the quality of a large representative part of the Nation's ground- and surface-water resources and to develop an understanding of the natural and human factors affecting the quality of these resources. This information will provide a sound scientific basis upon which water resources decision making at all governmental levels can be based. To meet its goals, the program will integrate water-quality information at local, regional, and national scales. The program will be perennial and consist of two major components -- study-unit investigations and national assessment activities. Investigations of surface- and ground-water resources of major regional hydrologic systems (river basins and aquifer systems) each covering 1200 to about 60,000 square miles, will be conducted on a rotating basis for 60 study units located throughout the Nation. Key findings from these study-unit investigations will be used along with other information to provide issue-oriented water-quality assessments of regional and national interest. application/pdf en Publ by ASCE National Water-Quality Assessment (NAWQA) program. A basis for water-resource policy development text