A watershed can be compared to a huge basin collecting all the precipitation that falls within it and carrying this to the common outlet. A watershed includes not only the land within its boundaries but also the surface water of lakes, streams and wetlands as well as the groundwater moving beneath the surface. Watersheds vary from the largest river basins to just a few acres in size.

Watersheds are natural systems that link the land and water resources and the living organisms, including people, within its boundaries. How we live on the land affects the quality and quantity of water resources within the watershed.