Watersheds 101

What IS A Watershed?

A watershed is an area of land from which all of the water drains to a common stream, river, or lake. The rainwater that runs across the ground (runoff) picks up pollutants as it goes. We all must do our part to reduce and slow down runoff pollution before it gets into the streams, rivers, and lakes. The picture to the left shows how an area drains, while the picture to the right is the Mississippi River basin, the largest watershed in the United States, draining >1 million square miles of land. Learn more here.

River Runner Visualization


Click to drop a raindrop anywhere in the contiguous United States and watch where it ends up!