American University’s documentary Keeping the Potomac: The Politics of Water will air January 24 at 7:30pm on Maryland Public Television, and again on Saturday, January 28 at 4:30pm. In May, it will also air in prime time as part of Maryland Public Television’s Chesapeake Bay Week. American University filmed Upper Potomac Riverkeeper Brent Walls, Shenandoah Riverkeeper Mark…