Nonpoint source (NPS) discharges to aquatic systems have been identified by the U.S. Environmental Protection Agency (USEPA) and other professional water quality scientists as important sources of polutants. In many cases, these pollutants interfere with the intended beneficial uses of these waterbodies. Indeed, this problem is of such widespread occurrence that Congress enacted Section 319 of the Clean Water Act (in 1987) and established a national program to assess and control NPS pollution.