A diffuse, scattered source of pollution. Nonpoint sources have no fixed location where they discharge pollutants into the air or water as do chimneys, outfall pipes, or other point sources. Nonpoint sources include runoff from agricultural fields, feedlots, lawns, golf courses, construction sites, streets, and parking lots, as well as emissions from quarrying operations, forest fires, and the evaporation of volatile substances from small businesses such as dry cleaners. Unlike pollutants discharged by point sources, nonpoint pollution is difficult to monitor, regulate, and control. Also, it frequently occurs episodically rather than predictably. Where treatment plants have been installed to control discharge from point sources, nonpoint sources can be responsible for most of the pollution found in bodies of water. As much as 90% of the pollution load in a body of water may come from nonpoint sources.

Nonpoint sources of water pollution. (Illustration by Hans & Cassidy.)

See Also

Water Pollution