National water-quality assessment program; the central Nebraska basins

In 1991, the U.S. Geological Survey began to implement a full-scale National Water-Quality Assessment 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-and ground-water 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 provide water-quality information that will be useful to policy makers and managers at the national, State and local levels. The NAWQA program will integrate water-quality information that has been generated from the different area scales into the national assessment. A major component of the program is study unit investigations, which comprise the principal building blocks of the program on which national-level assessment are based. The 60 study-unit investigations that make up the full-scale NAWQA program represent hydrologic system that include parts of most major river basins and aquifer systems. The study unit vary in size from 1,200 to more than 65,000 square miles incorporate about 60 to070 percent of the Nation's water use and population served by public water supplies. In 1991, the Central Nebraska Basins area was among the first 20 NAWQA study units selected for study under the full-scale implementation plan