Situational Awareness (Tuesday, 2025-12-16)
According to the Middle Atlantic River Forecast Center, no appreciable precipitation fell in the basin over the past 24 hours. Over the next 3 days, the average basin precipitation may be around 0.5 Inches.
Special Conditions
USGS stream gages at Little Falls and Point of Rocks are both currently being affected by ice and therefore have periods where data is not available. As such, flow estimates reported in these emails and Loudoun Water Potomac River flow values are estimated based on available data.
Daily flows:
Little Falls gage flow 2025-12-15: 905 MGD (approx. 1400 cfs)
Little Falls gage flow 2025-12-16: 860 MGD (est., based on recently available real-time data) (1330 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-12-15*:840 MGD (estimated at 1300 cfs)
Point of Rocks flow 2025-12-16*:840 MGD (est., based on last data available) (estimated at 1300 cfs)
*Point of Rocks flow is based on last data available at 12:30 am 12/15 due to ice affect
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-12-15: 0 MGD (0 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 (2025-12-15):
Fairfax Water Corbalis withdrawal - Potomac: 89 MGD
WSSC Water Potomac withdrawal: 153 MGD
Washington Aqueduct withdrawal - Great Falls: 119 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 12 MGD
Total Potomac withdrawal: 373 MGD
Total net Potomac withdrawal: 361 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR**: estimated at 1300 cfs
QPR, obs**: estimated at 1300 cfs
QPR, WS: 0 cfs
**Loudoun Water PR flow is based on last data available at Point of Rocks at 12:30 am 12/15 due to ice affect
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.