Land, Larry F.Jensen, Richard W. Russell W. Kiesling, and Frank S. ShipleyProceedings: The Second State of the Bay Symposium. February 4 - 6, 19932010-02-152010-02-151993http://hdl.handle.net/1969.3/24108pgs. 47-49In 1991, the U.S. Geological Survey (USGS) began implementation of a National Water Quality Assessment (NAWQA) program. The long-term goals of the program are to describe the status and trends in the quality of a large representative part of the Nation's surface-water and ground-water resources, and to provide a sound scientific understanding of the primary natural and human factors affecting the quality of these resources. A major component of the program is study-unit assessments, which will address local and State issues and comprise the principal building blocks for regional and National assessments. The 60 study units that comprise the program are hydrologic systems, which include parts of most major river basins and aquifer systems in the Nation. Planning, literature searches, and analysis of existing information have been in progress since implementation of the program.data collectionswater qualitynutrientspesticidesaquifersChapter