MathBench > Environmental Science

What's in your Watershed?

Outlining a watershed

Use your mouse to drag the thunderhead...

Basically, a watershed is all the land that contributes water to a given stream or river.  So in the animation above, we are looking at the cross-section of a watershed (shaped like a V) in the center, and bits of the watersheds on the left and right.

Since a watershed is defined by the point it drains to, watersheds are nested inside each other. For example, the College Park Campus is part of the Paint Branch Watershed.  But Paint Branch joins the Anacostia River, so the Paint Branch Watershed is nested inside the Anacostia Watershed, which is itself nested inside the Chesapeake Bay Watershed.  The Chesapeake Bay Watershed is not nested inside any other watershed, though – its outlet is the Atlantic Ocean.

It is surprisingly easy to outline a watershed – you just look for the first order streams and make sure you draw a line that goes around them. You can see this if you mouse over this image:


Give it a try yourself