American Rivers, a United States conservation organisation working to make every river clean and healthy for people and wildlife, has nominated the Potomac, the river that flows through Washington, DC as America’s most endangered river for 2026.
Sewage spills, aging pipe infrastructure, rising bacterial levels and increasing number of data centres threaten the Potomac, the organization has said.
American Rivers reviews nominations for ‘America’s Most Endangered Rivers’, a list that it brings out annually, from individuals and organisations across the country.
Rivers are selected based upon the following criteria:
A major decision that the public can help influence in the coming year.
The significance of the river to people and nature.
The magnitude of threat to the river and its communities.
According to American Rivers, the Potomac river basin is home to more than 6 million people across the states of Maryland, Virginia, West Virginia, Pennsylvania, and the federal capital of Washington, D.C.
The river serves as the primary source of drinking water for the nation’s capital and many other cities and towns. “Flowing over 380 miles from the Appalachian Highlands to the Chesapeake Bay, the Potomac’s tributaries include the Shenandoah, Monocacy, Anacostia, North Branch, and South Branch rivers. The river supports internationally renowned recreational trout fisheries in its headwaters and some of the East Coast’s most significant oyster, blue crab, and striped bass commercial fisheries. Residents and visitors in D.C. and across the watershed value the river for its recreation opportunities, including fishing, boating, swimming, hiking, and wildlife watching.”
But earlier this year, in the largest sewage spill in US history, a major wastewater pipe failed, sending 200 to 300 million gallons of untreated sewage into the Potomac and nearby C&O Canal.
“The January failure of the Potomac Interceptor sewage line in Montgomery County, Maryland, closed a stretch of river upstream of Washington, D.C. to all public access. The main drinking water collection point for Washington, D.C. is upstream of the spill and was not affected. But a smaller, secondary collection point downstream of the spill was shut down and out of service,” noted American Rivers’ report.
According to the organization, many of the region’s wastewater pipes, particularly in and around Washington, D.C., are approaching or have passed their 50-year service life.
“Bacteria levels in the Potomac River near the site of the spill were over 4,000 times higher than the safe recreational limit. Failure to address aging wastewater infrastructure on the Potomac puts the river at risk of ongoing contamination and threatens public health, local businesses, and wildlife,” said the report.
In addition, it said that the Potomac river watershed faces an unprecedented surge in data centre development, particularly in northern Virginia and portions of Maryland. “The region currently has over 300 data centres and is on track to have a total of about 1,000 centres occupying roughly 200 million square feet of buildings — enough to cover 3,472 football fields — on an estimated 20,000 acres of land. These facilities pose a significant and growing threat to both water quality and water quantity, yet are being approved without meaningful transparency, regulatory review, and assessment of cumulative impacts.”
American Rivers urged that the US Congress must invest to strengthen water infrastructure. As rapid development of data centres in the watershed poses an expanding threat to river health and the resilience of drinking water supplies, it added that state leaders must urgently establish common-sense safeguards on all data centres and evaluate cumulative impacts on water resources.
The other rivers in the list following the Potomac are the San Joaquin (California), Boundary Waters (Minnesota), the Lumber (North and South Carolina), the Rogue (Oregon), the Chilkat (Alaska), the Nissequogue (New York), the Dan (North Carolina and Virginia), the Amargosa (California and Nevada) and the Suwannee (Florida and Georgia).