Situational Awareness (Monday, 2025-12-15)
According to the Middle Atlantic River Forecast Center, trace amounts of precipitation fell in eastern portions of the basin over the past 24 hours. Over the next 3 days, no precipitation is anticipated. However, the week-long outlook expects a total of approximately 0.5 inches of precipitation in the basin.
Special Conditions
Flow data at the Little Falls gage has had two periods where "no data" is available over the past 24 hours due to ice. As such, flow data for Little Falls and Great Falls was approximated using available data.
Daily flows:
Little Falls gage flow 2025-12-14: approximately 1099 MGD (1700 cfs)
Little Falls gage flow 2025-12-15: approximately 911 MGD (est., based on recently available real-time data) (1410 cfs at 3:10 am)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-12-14: 1008 MGD (1560 cfs)
Point of Rocks flow 2025-12-15: 1138 MGD (est., based on recently available real-time data) (1760 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-12-14: approximately 1099 MGD (1700 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 (2025-12-14):
Fairfax Water Corbalis withdrawal - Potomac: 90 MGD
WSSC Water Potomac withdrawal: 148 MGD
Washington Aqueduct withdrawal - Great Falls: 122 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 12 MGD
Total Potomac withdrawal: 372 MGD
Total net Potomac withdrawal: 360 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1560 cfs
QPR, obs: 1560 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.