Wolf Trap National Park for the Performing Arts is locally part of the Difficult Run Watershed. Old Courthouse Creek which flows into Wolftrap Creek both flow through the park and drain into Difficult Run. The Difficult Run Watershed covering 58.3 square miles is the largest watershed in Fairfax County, Virginia. Difficult Run in turn drains into the Potomac River linking us to the Potomac Watershed. The Potomac Watershed is part of the Chesapeake Bay Watershed.