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What is Nonpoint Source Pollution?

Imagine that you are a raindrop. It begins to rain and you hit the ground and flow across streets, parking lots, yards, construction sites, farm fields, and even a golf course. Along the way, you pick up litter, oil, grease, metals, rubber, dirt, fertilizers, pesticides, animal waste, and other things left behind by people, automobiles, and animals. All of these pollutants mix with the rain and flow away as nonpoint source pollution.

Nonpoint source pollution occurs when runoff from rain and snowmelt carries pollutants into waterways such as rivers, streams, lakes, wetlands, and even groundwater. The name “nonpoint source pollution” is derived from the concept that there is no single point from which the pollution comes; it comes from everyone and everywhere. Nonpoint source (NPS) pollution is the nation’s and the state’s number one threat to water quality.

Examples of sources of NPS pollution in Illinois include runoff from farm fields, livestock facilities, construction sites, lawns and gardens, city streets and parking lots, surface coal mines, and forestry. The major sources of NPS pollution in Illinois are agriculture, urban runoff, and habitat modification. Urban runoff flows through storm drains and the vast network of pipes below our streets. Contrary to what most people think, water that flows into storm drains doesn’t pass through the sanitary sewer and get “treated.” It flows directly to lakes and streams. Habitat modification refers to the channelization of streams and the disturbance of riparian corridors (the area of land that is immediately adjacent to the banks of a stream). The most common NPS pollutants in Illinois are nutrients and sediment.

Nutrients come from fertilizers and animal waste, and they can do more than just turn the water green. An overabundance of nutrients can cause the over-fertilization of lakes and streams which leads to excess algae growth. After an algal bloom occurs, the algae eventually will die and be broken down by bacteria. All of that bacteria consumes oxygen making it difficult for fish and other aquatic life to survive.

Sediment is soil that has eroded from farm fields, construction sites, and streambanks. When sediment reaches our lakes and streams, it does more than make the water appear to be brown. Sediment causes the water to become cloudy, making it difficult for aquatic organisms to see and feed properly. Sediment can damage fish gills and the breathing of aquatic insects. Fish spawning habitat is covered by sediment, and sunlight penetration into the water is reduced which affects plant growth. Sediments can also carry other pollutants such as metals and toxic chemicals. If you have ever gotten stuck in the mud in a lake or river, you have seen the effects of sediment. It’s not much fun to swim, fish, or boat when too much sediment flows into water resources.