Maps
Potomac River Basin Drinking Water Source Protection Partnership
Potomac Watershed Map with Streams
Sub-watersheds of the Potomac River
Washington Metro Water Supply Service Areas (as of 2010)
USGS Potomac Watershed Stream Gages
Harmful Algal Bloom (HAB) Monitoring Locations
Additional maps can be found the Maps page of the Interstate Commission on the Potomac River Basin’s website.