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What is Nonpoint Source Pollution

When most people hear “water pollution,” they think of large pipes dumping tainted liquid into a lake or river. The Clean Water Act changed all of that by introducing the National Pollution Discharge Elimination System (NPDES). The NPDES program created a system to monitor water quality and limit water pollution discharges into waterbodies.

The Clean Water Act has been so successful at reducing pollution discharges from industries and municipalities (point sources) that the single largest source of water contamination today comes from nonpoint source pollution.

Nonpoint source pollution comes from oil, pet waste, pesticide, herbicide, fertilizer, road salt, bacteria, sediment, and any other contaminant that ends up on the ground naturally or from human activity. Rainwater and snowmelt picks up these contaminants as it washes over yards, sidewalks, driveways, parking lots, and fields and deposits them into Indiana’s lakes and streams as nonpoint source pollution. Common sources of nonpoint source pollution in Indiana include:

  • animal production operations and feedlots;
  • agricultural activities;
  • stream bank and shoreline erosion;
  • timber harvesting;
  • land development;
  • on-site sewage disposal units;
  • solid waste disposal landfills;
  • transportation-related facilities;
  • coal mining;
  • oil and gas production;
  • non-energy mineral extraction; and,
  • atmospheric deposition.

We tend to group together these sources of nonpoint source pollution into two major categories based on land use – agricultural and urban. Agricultural land is defined as land that is currently in production such as cropland, pastureland, rangeland, native pastureland, other land used to support livestock production, and tree farms. Urban land, in contrast, is forests, wetlands, minelands, and any other area that is developed for housing, roads and businesses (not used for agriculture). Many programs that provide assistance to clean-up nonpoint source pollution rely on these classifications. Learn more about nonpoint source pollution sources and how these can change water quality by reading the You, Me and Water Quality page.

Nonpoint source pollution can damage aquatic habitat, harm aquatic life, and reduce the capacity of water resources to be used for drinking water and recreation. There are a number of major types of nonpoint source pollutants in Indiana. Each of these can harm our rivers, streams, lakes, and wetlands. Fortunately, there are many ways to reduce or stop nonpoint source pollution, many of which are simple things we can do right in our own backyards.

No matter where you live in Indiana, you contribute to nonpoint source pollution. The good news is that there are simple things everyone can do to reduce our impact on water quality. However, the specific way you can help reduce nonpoint source pollution varies as much as the sources of nonpoint source pollution. Most important, there are numerous agencies, groups, and individuals who are working on the local level to clean up our rivers, lakes, streams, and wetlands.

Nonpoint Source Pollution: Additional Information

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