There are a number of different pollutants that can be picked up in stormwater and impact our land and water resources, including the following:
Sediment is often viewed as the largest pollutant load associated with stormwater runoff in an urban setting. Unprotected earth disturbances caused by human activities, including highway construction, land development, and poor installation and maintenance of vegetation, can create sediment pollution.
Sediment destroys the food supply for many species of fish by covering aquatic insect habitats on stream bottoms.
Sediment in rivers can cover the gravel that is used as a spawning habitat by some fish species.
Heavy sediment loads can clog fish gills.
Sediment reduces the amount of light penetrating the water, depriving aquatic plants of light needed for photosynthesis.
A number of pollutants often attach to and are moved in water by sediment particles.
Nutrients, Organic Matter, and Trash/Litter
Various forms of nutrients, organic matter, and trash may be carried by stormwater in urban areas. Consumption and decomposition of the nutrients and organic material by aquatic organisms can result in decreased oxygen levels, which, if they drop low enough, can severely impact water quality and plants and animals living in the water.
Phosphorus can attach to soil particles, and, if it enters a water body, can be used as fuel for the rapid growth of algae and aquatic plants. This can lead to a degradation of the water quality and interfere with human activities such as swimming, boating, and fishing.
Sources of organic matter include, but are not limited to leaking septic systems, garbage, and yard waste.
Some non-organic material, including plastic bags, six-pack rings, bottles, and cigarette butts, can be washed into the water and can choke, suffocate, or disable aquatic life such as ducks, fish, turtles, birds, and marine mammals.
Nutrients enter the urban system in a variety of ways, including from commercial and home landscaping practices, leaks from sanitary sewers and septic systems, and animal waste. The nutrients most often identified in stormwater runoff are phosphorus and nitrogen.
Excess nutrients can cause algae blooms (excessive growth of algae) and can occur in lakes, reservoirs, rivers, ponds, bays, and coastal waters. They can become harmful by producing toxins that harm human health and aquatic life. When the algae die after using up the nutrients, they sink to the bottom and decompose in a process which removes oxygen from the water. Fish and other aquatic organisms will die when the oxygen level falls too low.
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