Watershed boundaries are defined by the shape of the land (topography). This means that watersheds are like bathtubs. Imagine that the bathtub is the watershed, and the drain is the river. Any water that falls inside the tub (watershed) will eventually go down the drain (river) carrying dirt and soap with it. The high sides of the tub (like mountains and hills) keep the water from ending up on the floor (or in other watersheds).

Now, let's use the Potomac River as an example. ALL the water (from rain, snow melt, even sprinklers and hoses) that falls within the Potomac River watershed (no matter how far away from the river), will eventually travel all the way to the Potomac River. That means that everything that happens in the Potomac River Watershed has an impact on the River, and the Chesapeake Bay, too! This is because the Potomac River Watershed is part of the larger Chesapeake Bay Watershed.

Follow the Raindrop Road Trip to see how watersheds work and how we affect our river.