Sources and transport of phosphorus in the Western Lake Michigan Drainages

In 1991, the U.S. Geological Survey (USGS) began full implementation of the National Water-Quality Assessment (NAWQA) Program. The goals of the NAWQA program are to (1) provide a nationally consistent descrip- tion of water-quality conditions for a large part of the Nation's water resources, (2) define long-term trends (or lack of trends) in water quality, and (3) identify, describe, and explain, as possible, the major factors that affect the observed water-quality conditions and trends (Hirsch and others, 1988). To fulfill the goals of the NAWQA program, the USGS plans to examine 60 areas (study units) across the United States on a rotational cycle. The first 20 of these study units began intensive investigations in 1991. One of these study units is the Western Lake Michigan Drainages (WMIC) (fig. 1).