The City of Rockville gets all of its water from the Potomac River. The Potomac River Basin stretches across parts of four states (Maryland, Pennsylvania, Virginia and West Virginia) as well as the District of Columbia. The drainage area of the Potomac includes 14,670 square miles. Before reaching the Chesapeake Bay, the River stretches over 383 miles from Fairfax Stone, West Virginia to Point Lookout, Maryland. In terms of drainage area, this makes the Potomac River the fourth largest river along the Atlantic coast and the 21st largest in the Nation.

The Potomac's major tributaries include: the Anacostia River, Antietam Creek, the Cacapon River, the Monocacy River, the North Branch, the South Branch, the Occoquan River and the Shenandoah River. Smaller tributaries that run through the City of Rockville include Rock Creek, Cabin John and Watts Branch.

Over five million people live within the Potomac River watershed. Almost 86 percent of the watershed’s population receives its drinking water from the River. 

Additional information:

• Interstate Commission on the Potomac River Basin
• The State of Maryland’s source water assessment program
• The State of Maryland Water Supply program
• The Environmental Protection Agency’s source water protection page