Situational Awareness (Tuesday, 2026-09-15)
CO-OP is initiating daily drought monitoring and reporting today because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below 2000 cubic feet per second (cfs), CO-OP's daily monitoring threshold.
No precipitation was observed across the Potomac basin yesterday. The Middle Atlantic River Forecast Center indicates that 0.1 to 0.25 inches of rain is forecast over the next three days, with the largest amounts expected in the northwestern corner of the basin.
We appreciate your ongoing daily submission of withdrawal, storage, and discharge data. Please continue submitting these data and make sure they are sent by 8:00 am for the duration of this drought monitoring period. If you know of someone who would like to receive these emails but doesn’t appear to be on our distribution list, please let us know by emailing coop@icprb.org. Let us know if you no longer wish to receive emails from us. Should you have any questions or require further clarification, please do not hesitate to contact us at coop@icprb.org.
Special Conditions
Hydroelectric operations at Potomac Dam No. 4 have resulted in recent intra-daily flow fluctuations at downstream Potomac River gages, including Point of Rocks. Additional fluctuations are expected through December 15 due to seasonal operational changes for eel passage.
Daily flows:
Little Falls gage flow 2026-09-14: 1060 MGD (1640 cfs)
Little Falls gage flow 2026-09-15: 1060 MGD (est., based on recently available real-time data) (1640 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2026-09-14: 1267 MGD (1960 cfs)
Point of Rocks flow 2026-09-15: 1138 MGD (est., based on recently available real-time data) (1760 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2026-09-14: 1060 MGD (1640 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 (2026-09-14):
Fairfax Water Corbalis withdrawal - Potomac: 105 MGD
WSSC Water Potomac withdrawal: 156 MGD
Washington Aqueduct withdrawal - Great Falls: 147 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 420 MGD
Total net Potomac withdrawal: 413 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1960 cfs
QPR, obs: 1960 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.