As the major source of drinking water for the Metropolitan Washington area, the Potomac River basin is used as a case study to explore future impacts of rising temperatures on river flow.
Potomac River basin and freshwater portion of the watershed above Little Falls Dam (Source: Schultz et al. 2025).
ROCKVILLE, MD (July 1, 2025) – Recent hot weather has broken record highs and warm lows, according to The Weather Channel, with at least 160 million people in the United States under a heat alert last week.
A recently published article by Dr. Cherie Schultz and colleagues at the Interstate Commission on the Potomac River Basin’s (ICPRB) Section for Cooperative Water Supply Operations on the Potomac (CO-OP) looks at how warmer conditions may impact the water supply of the nation’s capital, especially in the face of increased variability in precipitation.
According to Dr. Schultz, “Estimating future water requirements in the region is a challenge but our research is one step closer to having a better idea of the region’s needs in the future. Our modeling indicates that the Potomac River will experience increasing drought severity caused by rising temperatures coupled with natural variability in precipitation.”
Precipitation is expected to increase by up to 16% by 2099 while annual river flows may decrease by as much as 49% by the same year due to the impacts of higher temperatures in the future. The increased rain does not mitigate the effects of extremely dry and hot months.
Dr. Schultz points out, “Rising temperatures will affect streamflow by increasing evaporative losses from soils and water surfaces and increase water demand from plants. Just like humans, plants get extra thirsty in the heat.”
The increased heat will change the timing and magnitude of snowmelt, as well.
ICPRB Executive Director Michael Nardolilli explains, “The Potomac River is a major source of water for the region and the only source of water for Washington, D.C. and Arlington, VA. Important research like this can inform planning decisions for the Washington, DC, metropolitan area’s cooperative regional water supply system. These predicted changes in river flows may necessitate new water supply infrastructure to ensure we can turn on our taps, even as obtaining federal funding for water infrastructure may become more challenging.”
The article, Is Hot Drought a Risk in the US Mid-Atlantic? A Potomac Basin Case Study, was published in the June edition of the Journal of the American Water Resources Association.
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The ICPRB is an interstate compact commission established by Congress in 1940. Its mission is to protect and enhance the waters and related resources of the Potomac River basin through science, regional cooperation, and education. Represented by appointed commissioners, the ICPRB includes the District of Columbia, Maryland, Pennsylvania, Virginia, West Virginia, and the federal government.