Education Home

All In the Watershed

What is a Watershed?

Stories Overview


Web of Life Places & Geology History Scientific Research Watershed Worries What You Can Do

What is a Watershed?

People use many different words for "watershed."

Some other words you may come across are:

  • river or lake basin
  • drainage area,
  • catchment area
  • headwaters (for an upper watershed),
  • river valley, or
  • a river and its tributaries.

A watershed is an area of land that captures water in any form, such as rain, snow, or dew, and drains it to a particular stream, river, or lake. All land is part of the watershed for some creek, stream, river or lake.

Some watersheds are immense; others are quite small. The Chesapeake Bay watershed is an area of 64,000 square miles and includes parts of six states (Maryland, West Virginia, Virginia, Delaware, Pennsylvania, and New York) and the entire District of Columbia.

But a watershed is more...

More than just an area of land, a watershed also provides us with a very useful way of looking at the area where we live. Rivers and lakes don't stop at a state border, and neither does a watershed. If you know in what watershed you live, you know your ecological address, so to speak.

Because all water in a watershed eventually drains into the same creek, river, lake, or bay, everyone in the watershed is connected through the water we use for drinking, recreational activities and industries.

No matter where you are,
you are in a watershed!

Watersheds and subwatersheds

Within the Chesapeake Bay there are many smaller watersheds, called subwatersheds. So in addition to living in the Chesapeake Bay watershed, you also live in, for example, the watershed of the Susquehanna River, the Anacostia River, the Severn River, or the Potomac River. These smaller watersheds are all part of larger watersheds and together form the 64,000-square-mile watershed of the Chesapeake Bay.