What is Runoff & Erosion?
Stormwater runoff and silt loads from erosion (i.e. increased turbidity) are examples of nonpoint source pollution. Nonpoint source (NPS) pollution, unlike pollution from industrial and sewage treatment plants, comes from many diffuse sources. NPS pollution is caused by rainfall or snowmelt moving over and through the ground. As the runoff moves, it picks up and carries away natural and human-made pollutants, finally depositing them into lakes, rivers, wetlands, coastal waters, and even our underground sources of drinking water.
These pollutants include:
Excess fertilizers, herbicides, and insecticides from agricultural lands and residential areas.
Oil, grease, and toxic chemicals from urban runoff and energy production.
Sediment from improperly managed construction sites, crop and forest lands, and eroding streambanks; - Salt from irrigation practices and acid drainage from abandoned mines.
Bacteria and nutrients from livestock, pet wastes, and faulty septic systems.
Atmospheric deposition and hydromodification are also sources of nonpoint source pollution.
EPA has a great web site where you can learn all about
NPS pollution at http://www.epa.gov/OWOW/NPS/!
Courtesy EPA's pollution brochure EPA-841-F-94-005, 1994, "Urban Stormwater Runoff".