Situational Awareness (Tuesday, 2026-09-22)
Between 0.1 and 2 inches of rain fell over the past 24 hours, with the greatest accumulations occurring in the northern portions of the basin. The next 3 days can expect to see an additional 0.5 to 2 inches of rainfall according to the Middle Atlantic Forecast Center predictions, with the Virginia and West Virginia portions of the basin expecting accumulations exceeding 1 inch.
Special Conditions
The U.S. Army Corps of Engineers, Baltimore District, reports that the final scheduled whitewater release from Savage River Dam for 2026 will occur on Saturday, September 26. The 2026 water-quality release schedule for Jennings Randolph and Savage reservoirs is available here: https://water.usace.army.mil/office/nab/releases/north-branch.
Intra-daily flow fluctuations at Potomac River gages, including Point of Rocks, are occurring due to upstream dam operations associated with eel passage.
Daily flows:
Little Falls gage flow 2026-09-21: 995 MGD (1540 cfs)
Little Falls gage flow 2026-09-22: 1487 MGD (est., based on recently available real-time data) (2300 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2026-09-21: 976 MGD (1510 cfs)
Point of Rocks flow 2026-09-22: 1099 MGD (est., based on recently available real-time data) (1700 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2026-09-21: 1008 MGD (1559 cfs)
Note: Estimated flow below Great Falls intake is flow at Little Falls plus Little Falls water supply withdrawal.
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2026-09-21):
Fairfax Water Corbalis withdrawal - Potomac: 98 MGD
WSSC Water Potomac withdrawal: 149 MGD
Washington Aqueduct withdrawal - Great Falls: 129 MGD
Washington Aqueduct withdrawal - Little Falls: 13 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 8 MGD
Total Potomac withdrawal: 401 MGD
Total net Potomac withdrawal: 393 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1510 cfs
QPR, obs: 1510 cfs
QPR, WS: 0 cfs
Note to Loudoun Water: See NWS ensemble flow forecasts (HEFS, GEFS, NAEFS) for Point of Rocks flow for the next 7 days – https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS. See US Army Corps of Engineers Potomac River Basin page for observed releases from Savage and Jennings Randolph reservoirs - https://water.usace.army.mil/office/nab/; See US Army Corps of Engineers North Branch Potomac River and Savage River page for scheduled releases - https://water.usace.army.mil/office/nab/releases/north-branch.
Note: Potomac River flow at Point of Rocks has dropped below the low-flow threshold of 2,000 cfs. When this occurs, per the Water Supply Coordination Agreement of 1982, CO-OP begins daily monitoring and reporting of Potomac flows and withdrawals on behalf of the CO-OP suppliers, Fairfax Water, Washington Aqueduct, and WSSC Water. Suppliers can review data at CO-OP's Data Portal at www.icprbcoop.org. Reports formatted in approved templates should be submitted by email to coop@icprb.org by 8:00 am for automated processing. Published monitoring reports are at http://icprbcoop.org/products/monitoring-reports.