Watershed Resources

Potomac Watershed Profile

The Watershed: The drainage area cover 14,760 sq. miles:

  • Maryland – 3,818 sq. miles
  • Virginia – 5,723 sq. miles
  • West Virginia – 3,490 sq. miles
  • Pennsylvania – 1,570 sq. miles
  • DC – 69 sq. miles

Landforms: The basin lies in five geological provinces:

  • Appalachian Plateau
  • Ridge and Valley
  • Blue Ridge
  • Piedmont Plateau
  • Coastal Plain

Length: 383 miles from the Fairfax Stone (West Virginia) to Point Lookout, Maryland

Major Tributaries:

  • Shenandoah River
  • South Branch River
  • Monocacy River
  • Savage River
  • Cacapon River
  • Anacostia River
  • Occoquan River
  • Antietam Creek
  • Conococheague Creek

Population: Approximately 6.11 million (2010 estimated census), of which 5.36 million live in the Washington, DC Metropolitan area.

Major Cities:

  • Bethesda, MD
  • Cumberland, MD
  • Hagerstown, MD
  • Frederick, MD
  • Rockville, MD
  • Waldorf, MD
  • Chambersburg, PA
  • Gettysburg, PA
  • Alexandria, VA
  • Arlington, VA
  • Harrisonburg, VA
  • Front Royal, VA
  • Harper’s Ferry, WVA
  • Charles Town, WVA
  • Martinsburg, WVA
  • Washington, D.C.

Water Flow: Average water flow is approximately 7 billion gallons per day. The largest flow measured at Washington, D.C., in March 1936, was 275 billion gallons per day. The lowest flow, in September 1966, was 388 million gallons per day before water supply withdrawals.