Location
The Cub Run and Bull Run watersheds (55.3 square miles and 9.7 square miles, respectively) are located in the southwestern part of Fairfax County bordering Loudoun and Prince William counties, upstream from Little Rocky Run.

Major Streams and Tributaries
Cub Run: Major tributaries include Big Rocky Run, Cain Branch, Dead Run, Elklick Run, Flatlick Branch and Round Lick Branch.
Bull Run: The major tributaries are Bull Run East and Bull Run West.

Unique Features
14 square miles of Loudoun County drains to these watersheds. While the impacts of these areas will be evaluated, the watershed plan does not extend into Loudoun County. These watersheds drain into the Occoquan Reservoir, which supplies drinking water for areas of Fairfax County and other local jurisdictions.