American Rivers has named the Potomac River the most endangered river in the United States for 2026 because of a major sewage spill earlier this year and the rapid growth of water-intensive data centers in the watershed.
The announcement came April 14, 2026, in Washington, DC. Betsy Nicholas, president of the Potomac Riverkeeper Network, highlighted the combined threats to water quality and availability in the river known as the Nation’s River.
The Potomac Interceptor sewer line collapsed January 19, 2026, along Clara Barton Parkway in Montgomery County, Maryland. The failure released an estimated 200 to 300 million gallons of untreated sewage into the Potomac River and the C&O Canal. Bacteria levels near the spill site reached nearly 12,000 times the safe recreational limit according to testing data.
DC Water, which operates the 54-mile Potomac Interceptor, constructed a bypass system within days to reroute flow. The line carries up to 60 million gallons of wastewater daily from parts of Virginia and Maryland to the Blue Plains Advanced Wastewater Treatment Plant in Southwest DC. The spill ranks among the largest in U.S. history and prompted federal involvement with the Environmental Protection Agency designated as lead agency.
Nicholas stated, “The Potomac is our Nation’s River. We must do all we can to protect it for this generation and those to come. We urge that lawmakers and regulators require investigation into data centers’ water use, toxins associated with them, and impacts on affected communities before hasty approvals of their construction cause irreparable harm.”
Pat Calvert, Virginia conservation director for American Rivers, added, “As the backdrop to our nation’s capital, the Potomac should reflect the highest standards of water health and stewardship. The Potomac is at an inflection point and cannot continue to sustain the rapid expansion of water-guzzling data centers drawing from its waters. Act now or watch this river be detrimentally redefined for the everyday citizen that depends on it.”
The region, often called Data Center Alley, already contains more than 300 data centers, primarily in Northern Virginia. Projections indicate as many as 1,000 facilities could occupy nearly 20,000 acres in coming years. Many proposed sites sit upstream of drinking water intakes serving millions of people. Concerns focus on increased stormwater runoff, chemical spill risks, hazardous materials management, groundwater withdrawals and flood potential without comprehensive watershed analysis.
David Flores, vice president and general counsel for the Potomac Riverkeeper Network, said, “The Potomac Interceptor failure was a wake-up call: hundreds of millions of gallons of sewage polluted this river, and our communities are still waiting for answers. We are working to ensure long-term impacts are fully addressed and that ongoing, transparent water quality monitoring continues.”
Nicholas concluded, “This crisis makes one thing clear. Failing wastewater infrastructure is polluting our rivers. Aging pipes are breaking, and without real investment and oversight, including federal and state investment, it will happen again. We need immediate action to fix these systems and ensure accountability, monitoring, and long-term restoration of the Potomac.”
Southern Maryland residents in Calvert, Charles and St. Mary’s counties depend on the Potomac and its tributaries as part of the larger Chesapeake Bay watershed. The river system supplies drinking water, supports commercial and recreational fishing, and drives tourism and quality of life across the region. Local communities monitor upstream conditions because pollution and water-use changes can affect downstream flows, oyster habitats, blue crab populations and bay restoration efforts funded through state and federal programs.
The announcement calls for stronger oversight of data center development and investment in aging wastewater infrastructure. American Rivers releases its annual list each spring to spotlight rivers at critical turning points and propose remedies for healthier waterways.
No specific new regulatory actions have been announced in direct response to the ranking as of April 14. The Potomac Riverkeeper Network continues independent water quality monitoring and advocates for transparent reporting on spill recovery and data center impacts.
The ranking places the Potomac ahead of nine other rivers on the 2026 list. It underscores ongoing challenges in balancing growth, infrastructure maintenance and environmental protection in the Washington metropolitan area and its surrounding watersheds.
