When it rains or snow melts, a significant amount of water is absorbed into the soil, stored as groundwater and slowly discharged into streams, lakes, seeps and springs. Water that does not soak into the ground is known as stormwater runoff, which flows over the land surface where it can absorb and transport pollutants such as nutrients, soil, trash, pesticides, oil and gasoline to our lakes, streams and wetlands. These materials that are carried away with the stormwater are called non-point source pollution and are some of the largest sources of pollution in our water bodies. These pollutants can harm people and animals.
Paved surfaces do not allow rainwater and snow melt to filter through the soil. Paved surfaces within a typical city block can generate five times more stormwater runoff than a forested area of the same size (Source: the United States Environmental Protection Agency). This excess water can cause flooding and lead to expensive repairs for both homeowners and municipalities. Although runoff from one property may not be substantial, the combined effect of an entire neighborhood can create a significant impact on local lakes and streams.
Impacts of runoff may include:
- Sediment is clouding the water, making it difficult for aquatic plants to grow.
- Sediment deposits are filling in fish spawning beds and deep pools and burying fish eggs.
- Excess nutrients are entering the water and causing increases in algae and aquatic plants.
- Bacteria and other pathogens are entering the water and potentially making people sick.
- Boating, swimming and other recreational activities are impaired.
- Pollution in the runoff can contaminate drinking water, increase treatment costs and affect human health.
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