The probability of water supply releases from backup reservoirs in the Washington metropolitan area during the summer and fall seasons of 2025 is currently above normal. Releases from Jennings Randolph and Little Seneca reservoirs are typically triggered when Potomac River flow falls below the combined water supply demand and the required environmental flow-by. Such low-flow conditions are often the result of below-normal precipitation and reduced groundwater levels. As of early April, streamflow is below normal, and groundwater levels are mostly below normal across the Potomac basin. The basin received only 1.7 inches of precipitation in March, which is 1.8 inches below normal. The 12-month cumulative precipitation deficit stood at 6.2 inches below normal as of March 31. Early April rain may ease the 12-month deficit. NOAA forecasts up to 1 inch more and expects El Niño to bring more extreme wet events. However, slow, steady storms are best for groundwater recharge.

The likelihood of natural Potomac flow requiring water supply augmentation by December 31 is currently estimated between 22 and 35 percent, which is higher than the historical range of 8 to 15 percent. Although current flows are sufficient to meet the Washington metropolitan area’s water demands without water supply releases from upstream reservoirs, drought conditions are forecasted to persist into the summer. The Metropolitan Washington Council of Governments’ drought watch, along with state-level drought watches and warnings in Maryland, Virginia, and Pennsylvania, remains in effect. Nonetheless, the region is well-prepared for drought conditions, with well-established contingency plans designed to safeguard the reliability of the Washington metropolitan area’s water supply.

Image: Adjusted flow at Little Falls on the Potomac River for 1999, 2002, 2024, and 2025 as of March 31, 2025.