Situational Awareness (Sunday, 2025-09-28)
Widespread rainfall fell across the basin over the past 24 hours, ranging from trace amounts to 0.5 inches. Over the next 72 hours, 0.1 to 0.25 inches is forecast for the southern portions of the basin.
Special Conditions
None
Daily flows:
Little Falls gage flow 2025-09-27: 1157 MGD (1790 cfs)
Little Falls gage flow 2025-09-28: 1280 MGD (est., based on recently available real-time data) (1980 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-27: 1254 MGD (1940 cfs)
Point of Rocks flow 2025-09-28: 1325 MGD (est., based on recently available real-time data) (2050 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-09-27: 1157 MGD (1790 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 (2025-09-27):
Fairfax Water Corbalis withdrawal - Potomac: 97 MGD
WSSC Water Potomac withdrawal: 125 MGD
Washington Aqueduct withdrawal - Great Falls: 120 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 354 MGD
Total net Potomac withdrawal: 347 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1940 cfs
QPR, obs: 1940 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.