The Environmental Protection Agency (EPA) divides water pollution sources into 2 categories: point and non-point. Point sources of water pollution are stationary locations such as sewage treatment plants, factories, and ships. Non-point sources are more diffuse and include agricultural runoff, mining activities, and paved roads.
Under the Clean Water Act, the National Pollutant Discharge Elimination System (NPDES) permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.
EPA works with state and local authorities to monitor pollution levels in the nation’s water and provide status and trend information on a representative variety of ecosystems. For more information, visit the EPA website.