Situational Awareness (Thursday, 2025-12-18)
According to the Middle Atlantic River Forecast Center, there was no observed precipitation in the basin over the past 24 hours. Between 0.25 and 1 inch of rain is possible over the next 3 days.
Special Conditions
Partial river flow values were available for the USGS stream gage at Point of Rocks yesterday, with limited availability due to ice. As a result, Point of Rocks flows were estimated for yesterday based on flows at the USGS’s gage at Shepherdstown, WV, (USGS Station No. 01618000) and a regression analysis of recent data. Flow values are available again at Point of Rocks today.
Daily flows:
Little Falls gage flow 2025-12-17: 950 MGD (1470 cfs)
Little Falls gage flow 2025-12-18: 911 MGD (est., based on recently available real-time data) (1410 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-12-17: 958 MGD (est. based on recently available flows at Shepherdstown) (1483 cfs)
Point of Rocks flow 2025-12-18: 1021 MGD (est., based on recently available real-time data) (1580 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-12-17: 950 MGD (1470 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 (2025-12-17):
Fairfax Water Corbalis withdrawal - Potomac: 92 MGD
WSSC Water Potomac withdrawal: 156 MGD
Washington Aqueduct withdrawal - Great Falls: 123 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 12 MGD
Total Potomac withdrawal: 383 MGD
Total net Potomac withdrawal: 371 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1483 cfs
QPR, obs: 1483 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.