Situational Awareness (Saturday, 2025-09-27)
Over the past 24 hours, the Potomac Basin received 0.1 to 0.75 inches, mainly in the southwestern headwaters, with little to none elsewhere. Over the next 72 hours, 0.1 to 1 inch is forecast across the basin, with the highest amounts in the southern areas.
Special Conditions
A whitewater release from Savage River Dam is scheduled for today, September 27th. The release is scheduled to be 1,000 cfs from 10am to 4pm. Flows will begin increasing at 6:30am and will return to 50 cfs after the event. Additional information can be found at https://www.nab-wc.usace.army.mil/nab/northBranch.html .
Daily flows:
Little Falls gage flow 2025-09-26: 1066 MGD (1650 cfs)
Little Falls gage flow 2025-09-27: 1118 MGD (est., based on recently available real-time data) (1730 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-26: 1209 MGD (1870 cfs)
Point of Rocks flow 2025-09-27: 1325 MGD (est., based on recently available real-time data) (2050 cfs)
Yesterday's estimated daily flows: Great Falls estimated flow 2025-09-26: 1066 MGD (1649 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 (2025-09-26):
Fairfax Water Corbalis withdrawal - Potomac: 98 MGD WSSC Water Potomac withdrawal: 152 MGD
Washington Aqueduct withdrawal - Great Falls: 154 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 0 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 404 MGD
Total net Potomac withdrawal: 398 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1870 cfs
QPR, obs: 1870 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://www.nab-wc.usace.army.mil/nab/poto.html; See US Army Corps of Engineers North Branch Potomac River and Savage River page for scheduled releases - https://www.nab-wc.usace.army.mil/nab/northBranch.html.
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.