Situational Awareness (Monday, 2025-09-15)
Potomac Rive flow continues to gradually decline. According to the Middle Atlantic River Forecast Center predictions, no rainfall is expected in the next 24 hours. Over the next 3 days, average basin rainfall may be between 0.1 and 0.75 inches, with more rainfall expected in downstream portions of the basin.
Special Conditions
None
Daily flows:
Little Falls gage flow 2025-09-14: 866 MGD (1340 cfs)
Little Falls gage flow 2025-09-15: 814 MGD (est., based on recently available real-time data) (1260 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-14: 1028 MGD (1590 cfs)
Point of Rocks flow 2025-09-15: 1008 MGD (est., based on recently available real-time data) (1560 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-09-14: 866 MGD (1340 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 (2025-09-14):
Fairfax Water Corbalis withdrawal - Potomac: 124 MGD
WSSC Water Potomac withdrawal: 143 MGD
Washington Aqueduct withdrawal - Great Falls: 139 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 417 MGD
Total net Potomac withdrawal: 411 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1590 cfs
QPR, obs: 1590 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.