In 1991, the U.S. Geological Survey (USGS) began to implement a full-scale National Water-Quality Assessment (NAWQA) program. The long-term goals of the NAWQA program are to describe the status and trends in the quality of a large, representative part of the Nation's surface- andgGroundwater resources and to provide a sound scientific understanding of the primary natural and human factors affecting the quality of these resources. In meeting these goals, the program will produce a wealth of water-quality information that will be useful to policy makers and managers at the national, State, and local levels.
A major design feature of the NAWQA program is the integration of water-quality information at different areal scales. The principal building blocks of the program are the study-unit investigations on which the national-level assessments are based. The 60 study-unit investigations that make up the program are hydrologic systems that include parts of the Nation's major river basins and aquifer systems. These study units include areas ranging from 1,200 to more than 65,000 square miles and incorporate about 60 to 70 percent of the Nation's water use and population served by public water supply. In 1991, the South Platte River Basin was among the first 20 NAWQA study units selected for study under the full-scale implementation plan.
1 U.S. Geological Survey, Box 25046, MS 415, Denver Federal Center, Lakewood, CO 80225