The health of Long Island Sound (LIS) is inextricably connected to the health of the watershed that surrounds it. Keeping a watershed, the area of land that drains into a common outlet such as a river, lake, bay or ocean, free of pollution is extremely important to the health of the entire ecosystem. Two types of pollution plague watershed health, “point source” and “nonpoint source” pollution. Point source pollution is pollution that comes from a single, identifiable source, such as a sewage treatment plant discharge pipe. This type of pollution is relatively easy to locate and control. Nonpoint source pollution, however, cannot be attributed to an identifiable, single point because it is the accumulation of many small pollution sources that enter the ecosystem from diverse and often unseen locations.
Stormwater “runoff” is the term given to precipitation as it flows over the surface of the land on its way to a water body. Runoff, which is not absorbed and filtered by the ground, has the potential to collect nonpoint source pollution on the ground and become contaminated as it travels downhill through a watershed. This water is not absorbed by the ground because the soil is either already saturated with water or is covered with an “impervious surface,” or an impenetrable material. Structures with impervious surfaces include roadways, rooftops, sidewalks, driveways, and parking lots. Research has shown that water quality in surface waters is related to the amount of impervious surface cover in a watershed. Poor water quality occurs when impervious surfaces cover 25 percent or more of the watershed, allowing runoff to move pollutants into the receiving water body.
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