ICPRB’s Section for Cooperative Water Supply Operations on the Potomac publish the Water Supply Outlook on a monthly basis between April and October of each year. It provides an update on the possibility of water supply releases from the area’s reservoirs based on long-term precipitation data, flows, and other information for the Potomac basin.

Summary/Conclusions
The Washington metropolitan area has an above-normal probability of releases from its backup water supply reservoirs for the fall of 2023. These releases typically occur in response to low flows resulting from insufficient summer precipitation and low groundwater levels. Due to a dry period, CO-OP Drought Operations occurred from August 25th to September 11th. However, the Potomac basin saw some relief after several rainfall events produced 4.3 inches of precipitation for September, exceeding the monthly average by 0.5 inches. Little Falls’ adjusted stream flows reached a low of 533 million gallons per day (MGD), peaked above average, and are now within the 10th to 50th percentile flow range. Groundwater levels have been slower to recover, and many wells used in ICPRB’s low-flow outlook are now approaching normal levels. This trend is also reflected in the U.S. Drought Monitor, with reduced areas in the basin in the abnormally dry, moderate drought, and severe drought categories. NOAA’s U.S. Seasonal Outlook remains optimistic about drought conditions improving. As flows return to median levels, Point of Rocks has reverted to a flow rate of approximately 2,000 cubic feet per second (cfs). This flow rate coincides with the established Daily Monitoring threshold, and on October 4th, the CO-OP Section resumed its daily drought monitoring and reporting. Currently, the Potomac River’s flows are adequate to meet the water demands of the Washington metropolitan area without requiring releases from upstream reservoirs. The region has drought-contingency plans to ensure water supply reliability and prevent shortages.

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ICPRB’s Section for Cooperative Water Supply Operations on the Potomac (CO-OP) was established to serve as a cooperative technical center on water resources in the Potomac basin.