5th Annual ICPRB Water Conference

The 2026 Potomac River Conference, organized by the Interstate Commission on the Potomac River Basin (ICPRB) was held in Poolesville, Maryland September 9^th 2026- conveniently located near nothing. I attended and found comfort in that all the regional water utilities were in various stages of planning to address this critical need for a sustainable and resilient water supply in the region. Experts from various sectors gathered to discuss the impacts of population growth, aging infrastructure, and the significant water demands of data center development. The event highlighted the necessity of regional collaboration and innovative strategies like expanding  water reuse to navigate future environmental uncertainties. Additionally, the conference showcased advancements in forecasting technology though none of the models are as yet particularly good at forecasting river flow. Groundwater research intended to improve long-term resource management is just beginning. Here is some of what we learned.

Navigating Water Supply Challenges in the Potomac River Basin

The Potomac River serves as the primary drinking water source for about 5 million residents across the Washington metropolitan area, supplying major regional utilities including Loudoun Water, Fairfax Water, WSSC Water, DC Water, and the Washington Aqueduct. The  2026 Potomac River Conference was titled "A Dry Horizon: The Future of Water Supply in the Potomac River Basin."

Surging Demand: Population Growth and the Data Center Boom

Regional water demand is being reshaped by expanding communities and rapid industrial development across Northern Virginia, Maryland, and Washington, D.C.:

• Population Growth and Demographic Forecasting: Utilities rely on regional planning data, such as the Metropolitan Washington Council of Governments' (MWCOG) Cooperative Forecasts of population, employment, and households, to project long-term drinking water demand. As metropolitan populations and demand grow, balancing baseline residential water needs against finite seasonal river flows becomes increasingly complex.
• Data Center Expansion: The rapid development of data centers—particularly in Virginia—has introduced substantial new water and energy demands. Conference sessions highlighting the "water-energy nexus" and data center impacts noted that cooling infrastructure puts unique pressures on both surface water supply systems and groundwater sustainability. The need for water for cooling  occurs exactly at the same time when seasonal water flow is lowest. Organizations such as the Piedmont Environmental Council and the Montgomery Countryside Alliance emphasized the importance of groundwater to the overall water supply and  highlighted how high-density data center corridors require careful resource management to prevent aquifer stress and local infrastructure bottlenecks.

Julie Bolthouse, Director of Land Use Piedmont Environmental Council, had some interesting points on the growing use of water in data centers. Google is the ONLY hyperscaler reporting water withdrawal and consumption for individual data center facilities. Here is what they reported for their water use in their Virginia facilities in 2024. You will note that 74-80% of the water use is consumptive and lost from the system:

 

From PEC Presentation J. Bolthouse

In 2019 Loudoun County total average daily system demand was closer to 20–25 MGD. Maximum day water demand at that time was around 40 million gallons per day. As data centers come on-line the water use grows. By 2025 average daily system demand was 29 MGD and maximum day water consumption was 50 MGD. Though, population in Loudoun is growing in Loudoun, it’s not driving this increase in water consumption. In addition, data centers are using an average of 2.2 MGD and a Maximum of 5.5 MGD of reclaimed water that is not being returned to the Potomac. That is somewhere around a 50% increase in water use in Loudoun County in 6 years.

Supply Stressors: Climate Change and Land Use Shifts

While demand grows, environmental and land use factors are altering how water flows into and through the Potomac watershed:

• A Wetter but More Variable Climate: Hydrological research presented by the USGS indicates that the Potomac Basin is transitioning toward a wetter but more variable hydrological regime. This shift introduces greater unpredictable variability—bringing intense precipitation events alongside heightened risk of sudden seasonal droughts. To adapt, regional stakeholders are developing advanced forecasting tools, including probabilistic deep-learning  streamflow models and National Weather Service Middle Atlantic River Forecast Center (MARFC) products for water supply and drought management. Nonetheless, the frequency of whiplash events- going from drought to flood has increase and supply risk could grow despite general wetness of the future climate.
• Land Use and Watershed Health: Land use transformation across rural and suburban areas directly impacts groundwater recharge and increases stormwater and wastewater infrastructure challenges. Assessments in counties like Loudoun and Montgomery stress that protecting local groundwater supplies and managing land development are vital to preserving overall river basin resilience.

Regional Solutions and Collaborative Planning

To protect the region's drinking water future, regional water authorities are pursuing coordinated operational strategies:

• Water Reuse and Storage Strategies: Integrated approaches such as Fairfax Water's indirect water reuse program in the Occoquan reservoir system demonstrate how indirect potable reuse enhances overall system reliability during low-flow conditions. During dry summers, UOSA provides upto 90% of the flow into the Occoquan Reservoir.
• Shared Vision Planning and Source Protection: Water suppliers are engaging in USGS Shared Vision Planning frameworks, coordinated reservoir release operations, and ICPRB land prioritization mapping to protect critical source water parcels throughout the watershed. Unfortunately, the planning departments of many counties do not appear to be focused on protecting critical source water parcels.

The reality is that an event like the Colonial Oil spill in 1993 which spilled 408,000 gallons of diesel/ fuel oil shut down the Fairfax Water Potomac Intake for two weeks could no longer be survived without disrupting water supply today. The Occoquan Reservoir/ Griffith Water Treatment plant and connection to the Aqueduct in Falls Church and Arlington could no longer supply their approximately 2 million customers.