Pesticides in ground water in the Western Lake Michigan Drainages, Wisconsin and Michigan, 1983-1995

Abstract

In 1991, the U.S. Geological Survey (USGS) began 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 surfaceand groundwater resources, and to identify, describe, and explain, if possible, the major factors that affect the observed water quality (Hirsch and others, 1988). The program consists of study-unit investigations that include parts of most major river basins and aquifer systems in the country. The Western Lake Michigan Drainages study unit encompasses a 20,000-square-mile area in eastern Wisconsin and the Upper Peninsula of Michigan that drains to Lake Michigan and Green Bay (figure 1). An important component of the NAWQA Program is the retrospective analysis of available water-quality data. One of the primary concerns in the Western Lake Michigan Drainages study unit is the effect of pesticides on ground-water quality. This fact sheet summarizes 32,064 synthetic-organic pesticide analyses and detections for ground-water samples collected from 4,155 wells in the study unit between 1983 and 1995 (figure 1 and table 1). The term pesticide in this fact sheet refers to both the parent product and its breakdown products, and includes herbicides, insecticides, and fungicides.