Potomac River Regional Authorities

The Potomac River flows through four states and the District of Columbia, making it one of the most jurisdictionally complex river systems in the United States. No single agency holds complete authority over its 14,670-square-mile watershed. Instead, governance is distributed across federal, interstate, state, and local bodies — each with distinct statutory mandates, enforcement powers, and geographic jurisdictions. Understanding which authority governs which activity is essential for permit applicants, local planners, environmental compliance officers, and anyone engaged in land use or water policy within the Washington MSA (47900).

The Interstate Framework

Interstate Commission on the Potomac River Basin (ICPRB)

The Interstate Commission on the Potomac River Basin is the principal interstate compact agency governing the Potomac. Congress approved the Potomac River Compact in 1940, and the ICPRB was formally established to coordinate water supply planning, water quality monitoring, and flow management among Maryland, Virginia, West Virginia, Pennsylvania, and the District of Columbia.

The ICPRB does not hold direct regulatory authority to issue or deny discharge permits, but it performs binding coordination functions under federal law. Its most consequential operational role is the Low Flow Allocation Agreement, under which the Commission coordinates withdrawals by the region's three largest water suppliers — Washington Aqueduct, Fairfax Water, and the Washington Suburban Sanitary Commission — to ensure combined daily withdrawals do not threaten minimum flow conditions. The Potomac serves as the primary drinking water source for approximately 6 million people in the greater Washington region (according to ICPRB).

Federal Authorities

U.S. Army Corps of Engineers — Baltimore District

The U.S. Army Corps of Engineers, Baltimore District regulates all construction, dredging, fill, and structural work within navigable waters of the Potomac under Section 10 of the Rivers and Harbors Act of 1899 and Section 404 of the Clean Water Act. Any alteration of the riverbed, banks, or adjacent wetlands within the tidal and navigable Potomac requires a permit from the Baltimore District. Nationwide Permits (NWPs) cover minor impacts, while Individual Permits are required for projects with potentially significant environmental effects. The Baltimore District's jurisdiction on the Potomac extends from the river's mouth at Point Lookout, Maryland, upstream through the Washington metropolitan reach.

National Park Service — C&O Canal National Historical Park

The National Park Service administers the Chesapeake & Ohio Canal National Historical Park along 184.5 miles of the Potomac's Maryland shoreline from Georgetown to Cumberland. Within this corridor, NPS land management authority governs public access, recreational use, and any proposed development or utility crossing that intersects federal parkland. Projects that cross the C&O Canal corridor require coordination with NPS under the National Environmental Policy Act (NEPA) and Section 106 of the National Historic Preservation Act.

U.S. Geological Survey

The U.S. Geological Survey operates a network of stream gauges throughout the Potomac basin, including the long-running gauging station at Little Falls, Maryland — the primary monitoring point used by water suppliers to track real-time river flow conditions. USGS data does not carry regulatory authority, but it forms the factual backbone for ICPRB allocation decisions, Army Corps permit reviews, and state water quality assessments.

State Regulatory Authorities

Virginia Department of Environmental Quality (VDEQ)

The Virginia Department of Environmental Quality administers the Virginia Water Protection Permit (VWPP) program, which covers impacts to state waters including Potomac tributaries and wetlands within Virginia's jurisdiction. VDEQ also issues Virginia Pollutant Discharge Elimination System (VPDES) permits for point-source discharges into Potomac tributaries. Localities in Northern Virginia — including Arlington, Alexandria, Fairfax County, and Prince William County — fall under VDEQ's compliance oversight for stormwater, wastewater, and construction activity.

Maryland Department of the Environment (MDE)

The Maryland Department of the Environment governs Potomac-related activity on the Maryland side through the Maryland Waterway Construction Permit program, the Nontidal Wetlands Protection Act, and the Maryland National Pollutant Discharge Elimination System (NPDES) program. MDE administers the Maryland Tributary Strategy for the Potomac watershed as part of the broader Chesapeake Bay restoration commitment. Montgomery County, Prince George's County, Frederick County, and Charles County — all within MSA 47900 — operate under MDE compliance frameworks for water quality and stormwater management.

Regional Coordination

Metropolitan Washington Council of Governments (COG)

The Metropolitan Washington Council of Governments does not hold regulatory authority over the Potomac, but it provides the primary regional planning forum where the District of Columbia and 24 local governments coordinate on water quality, land use, and environmental issues affecting the river. COG's Environment and Energy Planning Committee tracks regional stormwater and watershed data, and COG's Cooperative Forecasts form the demographic baseline used by state and federal agencies when projecting future water demand in the basin.

DC Water and Sewer Authority

DC Water operates the Blue Plains Advanced Wastewater Treatment Plant, the largest advanced wastewater treatment facility in the world by flow capacity at approximately 370 million gallons per day. Blue Plains discharges treated effluent directly to the Potomac tidal reach and holds a National Pollutant Discharge Elimination System permit under EPA Region 3 oversight. DC Water's infrastructure serves not only the District of Columbia but also portions of Montgomery and Prince George's Counties in Maryland and Fairfax County in Virginia.

Chesapeake Bay Program Connection

The Chesapeake Bay Program is a multi-jurisdictional partnership that includes EPA, Maryland, Virginia, Pennsylvania, Delaware, New York, West Virginia, and the District of Columbia. The Potomac is one of the Bay's largest tributary watersheds. Under the 2010 Chesapeake Bay TMDL (Total Maximum Daily Load), each jurisdiction within the Potomac basin carries enforceable pollution reduction targets for nitrogen, phosphorus, and sediment — obligations that flow down to state permit programs and local stormwater ordinances throughout MSA 47900.

References

• Interstate Commission on the Potomac River Basin
• National Park Service — Chesapeake & Ohio Canal National Historical Park
• U.S. Army Corps of Engineers — Baltimore District
• Metropolitan Washington Council of Governments
• Virginia Department of Environmental Quality
• Maryland Department of the Environment
• DC Water and Sewer Authority
• U.S. Geological Survey — Potomac River Basin
• Chesapeake Bay Program

The law belongs to the people. Georgia v. Public.Resource.Org, 590 U.S. (2020)