The Environmental Protection Agency (EPA) divides water pollution sources into two categories: point and nonpoint. Point sources of water pollution are stationary locations such as sewage treatment plants, factories and ships. Nonpoint sources are more diffuse.  In other words, there is no point that can be identified as the source of the pollution.  It can come from a variety of areas such as agricultural runoff, mining activities, construction activities, paved areas, and more. 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 them.  Below are links to federal regulations when it comes to water quality.

Summary of the Clean Water Act
The Clean Water Act establishes the basic structure for regulating discharges of pollutants into the waters of the US and regulating quality standards for surface waters.

What is Nonpoint Source (NPS) Pollution?
Questions and answers about nonpoint source pollution.

National Pollutant Discharge Elimination System (NPDES)
The National Pollutant Discharge Elimination System permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.

National Pollutant Discharge Elimination System (NPDES) Phase II

The National Pollutant Discharge Elimination System permit program controls water pollution by regulating point sources that discharge pollutants into waters of the United States.