National Water-Quality Assessment--Potomac River Basin
By J.M. Gerhart
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-water and Groundwater 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.
The design of the NAWQA program will enable water-quality information at different areal scales to be integrated. A major component of the design is the inclusion of study-unit investigations. These investigations comprise the principal building blocks of the program on which national-level assessment activities are based. The 60 study-unit investigations that make up the program are hydrologic systems that include parts of most major river basins and aquifer systems. Individual study units cover areas of 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 Potomac River basin was among the first 20 NAWQA study units selected for study under the full-scale implementation plan.