The Potomac River — the water supply for the nation’s capital and the site of the country’s largest sewage spill earlier this year — tops a conservation group’s annual ranking of most endangered rivers.
The waterway earned the dubious distinction on American Rivers’ list of most threatened waterways for 2026 due to the double threat of aging sewer infrastructure and the rapid build-out of data centers.
“The Potomac River is the economic lifeline and cultural heart of our nation’s capital,” the report states. “But earlier this year, the largest sewage spill in U.S. history fouled the Nation’s River, raising alarms for public health and aging water infrastructure.”
The Jan. 19 rupture in the Potomac Interceptor — a massive, 60-year-old pipeline that collects sewage from the Maryland suburbs — sent more than 200 million gallons of untreated waste into the river, spiking bacteria levels and prompting authorities to issue weekslong recreation advisories.
