what counties does the Patuxent river flow through
Patuxent River Watershed. The Patuxent River watershed in Montgomery County drains to two reservoir systems maintained by Washington Suburban Sanitary Commission (WSSC).These are the Triadelphia and Rocky Gorge Reservoirs.The Patuxent River begins in Frederick and then flows through seven counties: Howard, Montgomery, Prince George's, Anne Arundel, Charles, Calvert, and St. Mary's Counties.It is a major tributary to the Chesapeake Bay and has been the focus of inter-jurisdictional watershed protection since the early 1980's.atuxent River Watershed. The Patuxent River watershed in Montgomery County drains to two reservoir systems maintained by Washington Suburban Sanitary Commission (WSSC). These are the Triadelphia and Rocky Gorge Reservoirs.