A watershed is the land that drains into a body of water such as a stream, lake or wetland. Because water flows downhill, watershed boundaries are always located on the top of hills or mountains. Rain falling on one side of the hill will flow into one watershed, while rain falling on the other side of the hill will flow into another watershed. Any changes to the land in a watershed will affect the water body it drains into, such as a stream or pond.
As we develop land, creating more impervious surfaces such as roof tops, sidewalks and streets, rain water has less area to soak into the soil. Instead, it flows over streets and sidewalks into storm drains that empty into our waterways, sometimes at high velocities which can cause erosion.
Rainwater also picks up pollutants such as sediment from small construction sites, contaminants washed from streets, and fertilizers or pesticides washing from lawns. These pollutants then enter the stormwater system and are released into our waterways, without treatment. This type of pollutant is called non-point source pollution. It is one of the major threats to rivers today. Because non-point source pollution is not associated with a specific point of entry into a water body, it is more difficult to regulate than point source pollution, pollution from a designated source. By taking the necessary steps to minimize these sources of pollution, we can create a clean, beautiful environment for our future.