New ICPRB research on hot droughts, drought watch lifted, PFAS contamination study, and more, in this week’s Potomac News Reservoir – June 26, 2025 >>>

New research on how heat impacts our water supply

Almost 160 million people in the United States are under a heat alert this week. How does extreme heat impact our water supply, especially as variability increases into the future? Will we be able to turn our taps on to quench our thirst, cook dinner, or flush the toilet?

Estimating future water requirements in the region is a challenge, especially in the face of increased variability in precipitation and temperatures. A recently published article by Dr. Cherie Schultz and colleagues in ICPRB’s Section for Cooperative Water Supply Operations on the Potomac (CO-OP), explores the future risks and impacts of hot drought through the lens of the Potomac River basin.

Applying statistical modeling, the data indicate that, “future Potomac River flows will be impacted by ‘hot drought’, that is, increasing drought severity caused by rising temperatures coupled with natural variability in precipitation.” Even though precipitation amounts are expected to increase by up to 16% by 2099, annual river flows may decrease by as much as 49% by the same year due to extreme heat. The increased rain does not mitigate the conditions in the extremely dry and hot months.

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.

News Release
FOR IMMEDIATE RELEASE – June 20, 2025

Spring rainstorms have brought relief to the Washington Metropolitan area after almost a year of dry conditions.

ROCKVILLE, MD (June 20, 2025) – Very little rainfall and high temperatures during the summer of 2024 led officials to recommend residents use water wisely to reduce demand on the Potomac River. Today, acting in part due to a recommendation by the Interstate Commission on the Potomac River Basin (ICPRB), the Metropolitan Washington Council of Governments’ (COG) Drought Coordination Committee will be lifting the Drought Watch declaration that has been in place since July 2024.

The COG regional drought plan triggers a Drought Watch when the entire Metropolitan Washington region is considered in moderate drought conditions – or worse – on the National Weather Service U.S. Drought Monitor map. Last year’s Drought Watch was the first enacted since 2010.

“The recommendation of ICPRB was based on several factors,” explains Michael Nardolilli, the executive director of ICPRB, “The U.S. Drought Monitor map shows practically zero signs of drought in the Potomac River watershed. The recent rains have nearly erased the basin’s cumulative precipitation deficits. While spring rains are generally ineffective for groundwater recharge, given the amount of rain the basin has received over the past couple months, staff at ICPRB are optimistic that there will be continued improvement in groundwater levels.”

According to Dr. Cherie Schultz, director of ICPRB’s Section for Cooperative Water Supply Operations on the Potomac (CO-OP), “Even if we end up in a similar situation as last summer, with very little rainfall and record-breaking temperatures, the Washington Metropolitan area is well-prepared to withstand a drought due to decades of careful planning and strong partnerships among water utilities and government agencies.”

As part of a unique cooperative water supply system, Washington Metropolitan water suppliers share and jointly fund upstream drinking water reservoirs – constructed several decades ago – that can supplement river flow, if needed. The upstream reservoirs are currently full.

In addition to the Washington Metropolitan Drought Watch declaration being lifted, the Virginia Department of the Environment lifted all drought advisories for the Commonwealth. As of June 15, 2025, central Maryland remains in Drought Warning status according to the Maryland Department of the Environment.

Nardolilli urges residents to still conserve water when possible by taking simple actions such as turning off the faucet when not actively using it, limiting time in the shower, and only watering plants and lawns when needed.

“The Potomac River is the drinking water source for more than 5 million people in the Washington Metropolitan area and should be treated as a precious resource,” says Nardolilli.

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Click here for a PDF of News Release: Drought Watch Lifted for the D.C. Metro Area > > >

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.

Renee Bourassa, Communications Director

Interstate Commission on the Potomac River Basin | Rockville, MD

rbourassa@icprb.org | 301.417.4371 | website

Current drought status, salt crisis, data centers, and much more in the Potomac News Reservoir – June 5, 2025 >>>

River Report: Water supply outlook for June

Today’s U.S. Drought Monitor map of the Potomac watershed is a sight for dry eyes, with only 37% abnormally dry and 0% in all other categories.

Each month, ICPRB looks deeper into the data when staff at ICPRB’s Section for Cooperative Water Supply Operations on the Potomac (CO-OP) publishes a report exploring the current conditions and the probability of water supply releases from upstream reservoirs, which is an indicator of regional drought. In this River Report, we’ll highlight excerpts of the recently published June Water Supply Outlook.

The probability of needing water supply releases from the Washington metropolitan area’s backup reservoirs during summer and fall 2025 is elevated.

As of early June, drought conditions in the Potomac River basin have shown modest short-term improvement following above-normal rainfall in May. Data from the National Weather Service’s Middle Atlantic River Forecast Center (MARFC) show that the Potomac basin upstream of Washington, D.C., received 6.2 inches of precipitation in May—2.9 inches above normal. As of May 30, the 12-month cumulative precipitation is 34.5 inches, which is 4.9 inches below normal.

While recent rain has boosted streamflows and improved groundwater levels in some areas, conditions remain mixed, and improvements may be tapering off…long-term deficits persist. Drought watches and warnings remain in effect across parts of Maryland, Virginia, and Pennsylvania, including the ongoing MWCOG drought watch, expected to be reviewed in June or July.

According to recent U.S. Geological Survey (USGS) data, groundwater conditions across the region are mixed. Some wells remain much lower than normal, indicating ongoing dry conditions…other wells show higher-than-average levels, likely due to recent rainfall.

The Climate Prediction Center’s May 31 outlook indicates likely drought improvement in the Potomac River basin by late August. However, in their discussion the Center warns that long-term precipitation deficits—especially in parts of Maryland, West Virginia, and Pennsylvania—may persist due to low streamflows and groundwater levels, and that even brief periods of hot, dry weather could trigger a quick return of drought conditions.

If low-flow conditions develop, the region is protected by well-established drought contingency plans.

Best wishes in retirement

ICPRB staff would like to give a fond farewell to Andrea Nagel, our longtime Senior Environmental Scientist. Andrea retired last week after 24 years of service to ICPRB.

If you are familiar with ICPRB products, you have undoubtably admired her work. As a GIS expert, she was responsible for many of ICPRB’s informative maps highlighting features of the Potomac River watershed, as well as complex geospatial analyses required for ICPRB efforts like the land prioritization tool. She was the co-author of at least 22 ICPRB publications, many related to her technical work on TMDLs.

We all wish her the best of luck in her retirement!

ICPRB’s upcoming third quarter business meeting

The ICPRB Third Quarter Business Meeting is coming up on Tuesday, June 17, 2025. The meeting will be held virtually on Teams. Commissioners will discuss progress made on the Low Flow Allocation Agreement and get an update on ICPRB’s Land Use Webinar Series. Find the draft agenda on our Business Meetings page.

The public is invited to view the virtual meeting or provide public comment. Please contact us by Friday, June 13, for more information on how to attend.

ICPRB in the community

Please join us at one of our upcoming events:

• June 14 – Walk in the Woods: Potomac Fever (Chevy Chase, MD)
• Jul. 11 – RiverPalooza: Shenandoah Snorkeling Paddle (Bentonville, VA)

The ICPRB Third Quarter Business Meeting is coming up on Tuesday, June 17, 2025. The meeting will be held virtually on Teams. Commissioners will discuss progress made on the Low Flow Allocation Agreement and get an update on ICPRB’s Land Use Webinar Series. Find the draft agenda on our Business Meetings site on our webpage.

The public is invited to view the virtual meeting or provide public comment. Please contact us by Friday, June 13, for more information on how to attend.