About the Potomac Basin
Potomac River Basin Drinking Water Source Protection Partnership
The Potomac River basin stretches across parts of Maryland, Pennsylvania, Virginia, and West Virginia, as well as the District of Columbia. Encompassing 14,670 square miles, it includes all of the land area where water drains toward the mouth of the Potomac. Learn more about the Potomac watershed from the Interstate Commission on the Potomac River Basin.