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What is a watershed?

A watershed is the area of land where all of the water that is under it or drains off of it goes into the same place. John Wesley Powell, scientist geographer, put it best when he said that a watershed is:

"that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of a community."

Watersheds come in all shapes and sizes. They cross county, state, and national boundaries. In the continental US, there are 2,110 watersheds; including Hawaii Alaska, and Puerto Rico, there are 2,267 watersheds.

Watershed Illustration

Pennsylvania and the Chesapeake Bay

The Chesapeake Bay Watershed is the largest watershed in Pennsylvania. This large ecosystem encompasses approximately 64,000 square miles in six states: Maryland, Delaware, Virginia, West Virginia, Pennsylvania, New York and the District of Columbia.

Although Pennsylvania doesn't border the Chesapeake Bay, more than half of the state lies within the watershed. Pennsylvania contains two major rivers that are part of the Chesapeake Bay Watershed: the Susquehanna, with 21,000 square miles, and the Potomac, with 1,600 square miles. Together, they total 40 percent of the entire Chesapeake Bay watershed.

The Susquehanna River basin is the largest tributary of the Chesapeake Bay. From its start near Cooperstown, New York, the river flows over 400 miles and empties into the northern portion of the Chesapeake Bay in Maryland.

For more information on NRCS's Chesapeake Bay Conservation efforts, click here.