Washington’s Potomac River Named America’s Most Endangered, Threatened by Sewage and Data Center Boom

The Potomac River, a drinking water source for more than six million people across the Washington region, has been ranked the most endangered river in the United States for 2026.

The conservation nonprofit American Rivers made the designation on April 14, citing two compounding threats: a January sewage rupture that sent up to 300 million gallons of raw waste into the river, and the largely unregulated expansion of data centers across the watershed that is straining the river’s water supply.

The immediate crisis began when the Potomac Interceptor, a sewer main more than 60 years old running through Montgomery County, Maryland, collapsed in January. Bacteria levels near the rupture site climbed to nearly 12,000 times the safe recreational limit. Washington, D.C., officials lifted their public health advisory in early March, but the underlying problem remains: many of the region’s wastewater pipes have already exceeded their 50-year design life. “Aging pipes are breaking,” said David Flores of Potomac Riverkeeper Network. “Without real investment and oversight, it will happen again.”

The longer-term threat is the data center industry. The greater Washington area, nicknamed “Data Center Alley,” already hosts more than 300 facilities, with projections pointing toward 1,000 in the coming years. These installations consume millions of gallons of water daily for cooling. Loudoun County alone accounts for up to 8 percent of total Potomac basin water withdrawals during summer peaks, yet facilities are being approved without any watershed-wide review of their cumulative impact. Many sit upstream of drinking water intakes serving millions of Maryland and Virginia residents.

“We need to make certain that we’re not approving these without full assessment of their impacts,” said Pat Calvert, Virginia conservation director for American Rivers.

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American Rivers is calling on Congress to reauthorize two federal water infrastructure funding programs before they expire in September, and urging Maryland and Virginia to require water-use transparency and cumulative impact assessments before approving further data center construction.

“The Potomac is at an inflection point,” Calvert warned. “Act now or watch this river be detrimentally redefined for the everyday citizen that depends on it.”