Nitrate in ground water in the western Lake Michigan drainage basin, Wisconsin and Michigan

In 1991, the U.S. Geological Survey began the nationwide implementation of the 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- and ground-water resources and to provide a sound, scientific understanding of the primary natural and human factors that affect the quality of these resources. The program (as currently planned) consists of 60 study-unit investigations that include parts of most major river basins and aquifer systems in the country. The Western Lake Michigan Drainage Basin encompasses a 20,000-square-mile area in eastern Wisconsin and the Upper Peninsula of Michigan that drains to Lake Michigan and Green Bay (fig. 1).