Watershed 101

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What is a watershed? A watershed is an area of land that drains into a particular river, lake, or other body of water. Watersheds are sometimes called “basins” or “drainage basins.” We all live in a watershed. Some watersheds, like that of a stream or creek, are small. Others, like the Chesapeake Bay watershed, are large. 

The Chesapeake Bay watershed spans more than 64,000 square miles. It encompasses parts of six states—Delaware, Maryland, New York, Pennsylvania, Virginia, and West Virginia—and the entire District of Columbia. More than 18 million people call the Bay watershed home. The Chesapeake Bay is an estuary meaning it is a body of water where fresh and salt water mix. It is the largest of more than 100 estuaries in the United States and third largest in the world. The Bay receives about half its water volume from the Atlantic Ocean in the form of saltwater. The other half (freshwater) drains into the Bay from the enormous 64,000-square-mile watershed. The Susquehanna River is the Bay’s largest tributary, and contributes about half of the Bay’s freshwater. This is why our actions on land have such a big impact on the Bay’s health.