Basic Information about Nonpoint Source (NPS) Pollution

Overview

NPS pollution generally results from land runoff, precipitation, atmospheric deposition, drainage, seepage or hydrologic modification. 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 ground waters.

Nonpoint source pollution can 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

States report that nonpoint source pollution is the leading remaining cause of water quality problems. The effects of nonpoint source pollutants on specific waters vary and may not always be fully assessed. However, we know that these pollutants have harmful effects on drinking water supplies, recreation, fisheries and wildlife.

Nonpoint Sources vs. Point Sources

The term "nonpoint source" is defined to mean any source of water pollution that does not meet the legal definition of "point source" in section 502(14) of the Clean Water Act:

The term "point source" means any discernible, confined and discrete conveyance, including but not limited to any pipe, ditch, channel, tunnel, conduit, well, discrete fissure, container, rolling stock, concentrated animal feeding operation, or vessel or other floating craft, from which pollutants are or may be discharged. This term does not include agricultural storm water discharges and return flows from irrigated agriculture.

Watershed Showing nonpoint and point sources — **Illustrations of nonpoint and point source pollution along with elements of the hydrologic cycle.**
*Developed by the EPA, Office of Water, Nonpoint Source Program*

Download the above diagram in a screen-reader compatible format: Sources of Pollution Diagram (pdf) (2.13 MB, November 2024)

What You Can Do to Prevent Nonpoint Source (NPS) Pollution

In Urban Environments
Mining
Forestry
Agriculture

In Urban Environments

Keep litter, pet wastes, leaves and debris out of street gutters and storm drains—these outlets drain directly to lake, streams, rivers and wetlands.
Apply lawn and garden chemicals sparingly and according to directions.
Dispose of used oil, antifreeze, paints and other household chemicals properly—not in storm sewers or drains. If your community does not already have a program for collecting household hazardous wastes, ask your local government to establish one.
Clean up spilled brake fluid, oil, grease and antifreeze. Do not hose them into the street where they can eventually reach local streams and lakes.
Control soil erosion on your property by planting ground cover and stabilizing erosion-prone areas.
Encourage local government officials to develop construction erosion and sediment control ordinances in your community.
Have your septic system inspected and pumped, at a minimum every three to five years, so that it operates properly.
Purchase household detergents and cleaners that are low in phosphorous to reduce the amount of nutrients discharged into our lakes, streams and coastal waters.

Mining

Become involved in local mining issues by voicing your concerns about acid mine drainage and reclamation projects in your area.

Forestry

Use proper logging and erosion control practices on your forest lands by ensuring proper construction, maintenance, and closure of logging roads and skid trails.
Report questionable logging practices to state and federal forestry and state water quality agencies.

Agriculture

Manage animal manures to minimize losses to surface water and ground water.
Reduce soil erosion and nutrient loss by using appropriate conservation practice systems and other applicable best management practices.
Use planned grazing systems on pasture and rangeland.
Dispose of pesticides, containers, and tank rinsate in an approved manner.
Work with conservation partners locally including Soil and Water Conservation Districts to understand local strategies.

Fact Sheets

Current Fact Sheets about Runoff and NPS Pollution

Protecting Water Quality from Agricultural Runoff (PDF) (2 pp, 12 K) This is a fact sheet about how agricultural runoff affects water quality (March 2005, EPA 841-F-05-001).
Protecting Water Quality from Urban Runoff (PDF) (2 pp, 13 K) This is a fact sheet about how urban runoff affects water quality (February 2003, EPA 841-F-03-003).
Brochure: "After the Storm" (PDF) (4 pp, 14 K) This brochure provides a broad overview of stormwater pollution, including runoff from residential and commercial properties, farms, construction sites, automotive facilities, forestry operations and others (January 2003, EPA 833-B-03-002).
Bookmark: "10 Things That You Can Do to Prevent Stormwater Runoff Pollution" (PDF) (2 pp, 14 K) This handy bookmark lists 10 simple things anyone can do to prevent stormwater pollution (February 2003, EPA 841-H-03-003).
Stormwater Management at the EPA Headquarters Office Complex (PDF) (4 pp, 10 K) This page highlights the Ariel Rios South Building Courtyard demonstration project at the EPA Headquarters complex that incorporates environmentally sound building and landscaping techniques.

NPS Pollution Pointers (Legacy Fact Sheets from 1996)

Pointer No. 1: Nonpoint Source Pollution: The Nation's Largest Water Quality Problem (PDF) (2 pp, 96 K)This fact sheet provides background information on nonpoint source pollution (EPA 841-F-96-004A).
Pointer No. 2: Opportunities for Public Involvement in Nonpoint Source Control (PDF) (2 pp, 96 K)This fact sheet provides information on the ways the public can help control nonpoint source pollution (EPA 841-F-96-004B).
Pointer No. 3: Programs for Nonpoint Source Control (PDF) (2 pp, 96 K)This fact sheet lists the federal programs that address nonpoint source pollution (EPA 841-F-96-004C).
Pointer No. 4: The Nonpoint Source Management Program (PDF)(2 pp, 96 K) This fact sheet provides background on Section 319 of the Clean Water Act (EPA 841-F-96-004D).
Pointer No. 5: Protecting Coastal Waters from Nonpoint Source Pollution (PDF) (2 pp, 96 K) This fact sheet provides information on nonpoint source pollution’s impact on coastal areas and the federal actions that have been taken to address this issue (EPA 841-F-96-004E).
Pointer No. 6: Managing Nonpoint Source Pollution from Agriculture (PDF)(2 pp, 108 K) This fact sheet addresses the impact of agricultural practices on nonpoint source pollution and the positive steps that can be taken to reduce agriculture’s impact (EPA 841-F-96-004F).
Pointer No. 7: Managing Urban Runoff (PDF)(2 pp, 96 K) This fact sheet addresses the impact of urban runoff on waterway health (EPA 841-F-96-004G).
Pointer No. 8: Managing Nonpoint Source Pollution from Forestry (PDF) (2 pp, 96 K) This fact sheet addresses the impact of forestry practices on nonpoint source pollution and positive steps that can be taken to reduce forestry’s impact (EPA 841-F-96-004H).
Pointer No. 9: Managing Nonpoint Source Pollution from Boating and Marinas (PDF)(2 pp, 96 K) This fact sheet addresses the impact of boating and marinas on nonpoint source pollution and positive steps that can be taken to reduce their impact (EPA 841-F-96-004I).
Pointer No. 10: Managing Nonpoint Source Pollution from Households (PDF) (2 pp, 96 K) This fact sheet describes ways a homeowner can reduce nonpoint source runoff from their property (EPA 841-F-96-004J).
Pointer No. 11: Managing Wetlands to Control Nonpoint Source Pollution (PDF) (2 pp, 96 K) This fact sheet provides information on the importance of wetlands in preventing nonpoint source pollution from degrading water quality (EPA 841-F-96-004K).