Potomac River Facts

River FactsLength (from the Fairfax Stone in WV to the mouth at the Chesapeake Bay): 382 miles.

Width (at its mouth, measured between Point Lookout in MD and Smith Point in VA): 11.3 miles.

Average width (from Washington to Harpers Ferry): 1,500 feet.

Elevation (at the Fairfax Stone): 3,125 feet above sea level.

Drainage area: 14,670 square miles. Virginia = 5,723 square miles, Maryland = 3,818 square miles, West Virginia = 3,490 square miles, Pennsylvania = 1,570 square miles, and Washington DC = 69 square miles.

Water Flow: Average flow is approximately 7 billion gallons per day. The largest flow measured at Washington, DC, in March 1936 was 275 billion gallons per day. The lowest flow in September 1996, was 388 millon gallons per day before water supply withdrawals.

Water Supply Withdrawals: 486 million gallons are taken out of the river for drinking water every day for the DC area. Over 5 millions people in the Potomac watershed get their drinking water from the Potomac River or one of its tributaries.

Pollution Loads: While the Potomac River and its tributaries contribute just 25% of the water flow to the Chesapeake Bay, they are responsible for 28% of the nitrogen, 33% of the phosphorous, and 34% of the total sediment loads into the Bay. 

List of Tributaries

Alexandra Cousteau's Expedition Blue Planet's Our Nation's River: A System on the Edge. (video)

The Nature Conservancy's The Potomac Gorge -- Watching the River Flow (video)

American Rivers' Most Endangered Rivers 2012 -- report listing the Potomac as #1

photo by Ed Neville