What is a Watershed?

Map of the Susquehanna River watershed

The area of land that drains into streams, lakes, estuaries or other bodies of water are known as watersheds. They are also known as drainage basins or catchments.

As precipitation falls to the ground, the water is pulled downhill by gravity, which causes it to flow over the landscape or infiltrate through the soil into the groundwater.

Topography — the hills, valleys, and other features that define the landscape — determine the boundaries of watersheds.

Every stream, regardless of its size, has a watershed. Smaller watersheds are contained within larger watersheds. For example, the French Creek watershed in southeastern Pennsylvania is part of the Schuylkill watershed, which in turn is part of the Delaware River Watershed, which is part of the Delaware Bay watershed.

No matter where you live, you live within a watershed. Just as you have a home and school address, you also have a watershed address. Use the US EPA Surf Your Watershed tool to find your watershed address.