In 1977, the Nonpoint Source Pollution Program was created to protect Wisconsin waters from runoff pollution by offering to share costs with landowners and communities that take steps to keep soil, fertilizer, street debris and construction site dirt from washing into streams and lakes.

Nonpoint source pollution is now considered to be the state's greatest water quality concern, degrading or threatening about 40 percent of the streams, about 90 percent of inland lakes, many of the Great Lakes harbors and coastal waters, and a substantial portion of groundwater resources in the state.

Source: http://dnr.wisconsin.gov/org/water/division/yow/milestones.pdf