Situational Awareness (Friday, 2025-09-19)
No precipitation fell in the past 24 hours. Flows at Point of Rocks remain above the 2,000 cfs daily monitoring threshold but are expected to decline in the coming days. Forecasts from the Middle Atlantic River Forecast Center call for light rainfall of 0.01 to 0.1 inch over the next three days, with basin-wide totals of 0.01 to 0.5 inch expected over the week ahead.
Special Conditions
None
Daily flows:
Little Falls gage flow 2025-09-18: 1344 MGD (2080 cfs)
Little Falls gage flow 2025-09-19: 1913 MGD (est., based on recently available real-time data) (2960 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-18: 1545 MGD (2390 cfs)
Point of Rocks flow 2025-09-19: 1428 MGD (est., based on recently available real-time data) (2210 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-09-18: 1344 MGD (2079 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 (2025-09-18):
Fairfax Water Corbalis withdrawal - Potomac: 89 MGD
WSSC Water Potomac withdrawal: 136 MGD
Washington Aqueduct withdrawal - Great Falls: 139 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 376 MGD
Total net Potomac withdrawal: 369 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 2390 cfs
QPR, obs: 2390 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.