What Is Stormwater Runoff?


(Conservation Currents, Northern Virginia Soil and Water Conservation District)

Stormwater is water from precipitation that flows across the ground when it rains or when snow and ice melt. Some of the water seeps into the ground. Water that is not absorbed and thus flows across the surface to storm drains, streams, and rivers is called runoff.

Runoff can pose a threat to the quality of water in our streams and rivers because of the pollution it carries. Every drop of precipitation that strikes the soil loosens particles that wash away and end up as sediment in streams. Sediment and other debris clog fish gills, damage fish habitat, and block the light needed for plants to survive.

In addition to sediment, runoff carries other pollutants it encounters on the ground and pavement. Common pollutants include oil, gasoline, and antifreeze dripped by cars and trucks; chemicals used on lawns and gardens; litter from improperly disposed trash; and livestock and pet waste.

What can an individual do to reduce the pollutants in stormwater runoff?

  • Landscape with grass, shrubs, trees, and other plants to hold the soil together, lessening the chance of erosion.
  • Retain and maintain natural wooded areas, including the forest floor, to filter runoff.
  • Use mulch and other soil amendments to increase absorption of runoff.
  • Pick up pet waste and dispose of it with your household garbage.
  • Have your soil tested every three years and fertilize accordingly.
  • Recycle used motor oil, and keep your car in good repair.
  • And always remember that storm drains are not trash cans. They lead directly to streams, depositing runoff and all of the pollutants carried with it.  Please don’t dump in storm drains!

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