Situational Awareness (Tuesday, 2025-09-16)
Minimal precipitation fell in the past 24 hours, and flows continue to decline. The Middle Atlantic River Forecast Center projects little additional rainfall over the next 24 hours. In the 3- to 7-day outlook, basin totals are expected to range from 0.1 to 0.75 inches, with heavier amounts in the lower Potomac and lower overall averages across the basin.
Special Conditions
None
Daily flows:
Little Falls gage flow 2025-09-15: 801 MGD (1240 cfs)
Little Falls gage flow 2025-09-16: 789 MGD (est., based on recently available real-time data) (1220 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-15: 989 MGD (1530 cfs)
Point of Rocks flow 2025-09-16: 918 MGD (est., based on recently available real-time data) (1420 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-09-15: 801 MGD (1239 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 (2025-09-15):
Fairfax Water Corbalis withdrawal - Potomac: 130 MGD
WSSC Water Potomac withdrawal: 156 MGD
Washington Aqueduct withdrawal - Great Falls: 137 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 435 MGD
Total net Potomac withdrawal: 428 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1530 cfs
QPR, obs: 1530 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.