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Polluted Runoff: Nonpoint Source (NPS) Pollution

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:

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.

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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.

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

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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.

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Mining

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

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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.

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Agriculture

  • Manage animal manures to minimize losses to surface water and ground water.
  • Reduce soil erosion and nturient 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.

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Fact Sheets

Current Fact Sheets about Runoff and NPS Pollution

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NPS Pollution Pointers (Legacy Fact Sheets from 1996)

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