Study shows potential future vulnerabilities in D.C. area water supply

by Shannon Heckt, Virginia Mercury
December 18, 2025

For residents of the Washington metro area including Virginia’s Arlington, Fairfax, and Loudoun Counties, the majority of their water supply comes from one place – the Potomac River. A recent study by the Interstate Commission on the Potomac River Basin found that climate change and data centers could create major challenges down the road for the water source.

“We’re 100% dependent on the Potomac River, and only have a one day backup water supply that’s close at hand, and those are two conditions that are not found in any other major city in the United States,” said Michael Nardolilli, executive director of the commission.

The report, which is conducted by the commission every five years, found that the region will have more than enough water most years in the future. But there is a growing chance that there may not be enough water to meet user demand or manage the aquatic habitats downstream in future decades. The study indicated a 1% increase in that risk in 2030 and a 5% increase in 2050.

The population in the Washington metropolitan area has steadily been growing for years but water use has stayed relatively stable. But now researchers expect a 17% water use increase by 2050. With potential droughts in the future due to a changing climate, the river’s flow could be impacted and create a major challenge for the area. Man-made environmental disasters could also occur that affect water supply, a possibility researchers are preparing for. 

“As the seat of the federal government, we could have a contamination event that’s deliberate, and we could also have a contamination event that’s accidental, say, a trail derailment at Harpers Ferry,” Nardolilli said. “So we are working with the Army Corps of Engineers to try to look at these different options for making the water supply more resilient.”

There are some backup options to help meet demand if the Potomac gets too low to pull water from upstream reservoirs – Jennings Randolph and Little Seneca in Maryland. 

But it takes multiple days to get the water delivered. Other options for additional help could come from Fairfax Water’s Occoquan reservoir and WSSC Water’s Patuxent reservoir. There is only enough back up water available in the Washington area to last for one day, the research showed.

With these increased risks projected, the commission is urging local, state and regional governments to plan for more back up water sources. The U.S. Army Corps of Engineers has launched a feasibility study to look at water resiliency options. But with federal funding in limbo, it could delay the findings. There are multiple bills moving through Congress that, Nardolilli said, would contain funds for the feasibility study. 

There are two drinking water reservoirs in the planning stages in Loudoun and Fairfax that should be operational in 2028 and 2040, respectively. 

A different study found that should there be a significant disruption to the water supply, it could lead to an estimated $15 billion in gross regional product and tax loss within a month. 

The growth of data centers in the area has also raised concerns about how much water from the river is being used to cool the centers. The exact amount of water that is used for individual data centers is often shrouded in secrecy – which Nardolilli said creates a challenge of trying to accurately project the water needs of the region.

“When the rivers have the lowest flow, the data centers would have the highest demand for water,” Nardolilli said. “That combination gives us some pause. You know, looking at the numbers right now, it’s a very manageable situation, but if the data centers continue to grow, that puts an additional strain on the system.”

YOU MAKE OUR WORK POSSIBLE.

SUPPORT

Virginia Mercury is part of States Newsroom, a nonprofit news network supported by grants and a coalition of donors as a 501c(3) public charity. Virginia Mercury maintains editorial independence. Contact Editor Samantha Willis for questions: info@virginiamercury.com.