Situational Awareness (Thursday, 2025-09-11)
In the past 24 hours, 0–0.25 inches of rain fell in the lower basin near Washington, DC. Forecasts indicate less than 0.1 inches of precipitation, limited to the metro area, over the next day, and approximately 0 inches expected across the basin for the week.
Special Conditions
None
Daily flows:
Little Falls gage flow 2025-09-10: 989 MGD (1530 cfs)
Little Falls gage flow 2025-09-11: 957 MGD (est., based on recently available real-time data) (1480 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-10: 1105 MGD (1710 cfs)
Point of Rocks flow 2025-09-11: 1099 MGD (est., based on recently available real-time data) (1700 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-09-10: 989 MGD (1530 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 (2025-09-10):
Fairfax Water Corbalis withdrawal - Potomac: 118 MGD
WSSC Water Potomac withdrawal: 131 MGD
Washington Aqueduct withdrawal - Great Falls: 135 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 396 MGD
Total net Potomac withdrawal: 389 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1710 cfs
QPR, obs: 1710 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.