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Tri-County/City Soil & Water Conservation District . . . . . providing grassroots solutions to conserve natural resources |
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What is Non-Point Source Pollution ?
Non-Point Source Pollution is a type of pollution that doesn't come from a single source, or point, such as a sewage treatment plant or an industrial discharge pipe. In Virginia, NPS pollution occurs mainly through stormwater runoff. When it rains, runoff from farmland, city streets, construction sites, and suburban lawns, roofs, and driveways enters our waterways. This runoff sometimes contains harmful substances and solids. NPS pollution's effects seldom show up overnight -- they often go unnoticed for years. This characteristic makes it all the more difficult to control. There are four major forms of NPS pollution: sediments, nutrients, toxic substances, and pathogens. Pathogens and toxic substances have a very direct effect: They impair or destroy aquatic life. Sediment and nutrients have less obvious effects. Life in Virginia's rivers, streams, lakes, and bays could not exist without nutrients, but too much of a good thing often causes more harm than good. Nutrients over-enrich our waterways causing algal blooms which deplete oxygen. This makes the oxygen unavailable to fish and shellfish so they suffocate and die. The algae also cloud the water and coat underwater vegetation, cutting much-needed sunlight. Sediment clouds water too but also obstructs waterways, clogs sewers, interferes with navigation, and smothers fish and shellfish spawning grounds. Natural erosion and sedimentation occur at a lower rate than that resulting from man's land altering activities. Underwater plants and aquatic animals are particularly threatened by NPS pollution. Oysters, shad, herring, striped bass, and submerged aquatic vegetation -- considered by many to be the foundation of a stable aquatic ecosystem -- are damaged by this obscure pollution.
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