Situational Awareness (Tuesday, 2025-09-02):
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 2,000 cubic feet per second (cfs), CO-OP's daily monitoring threshold.
According to National Weather Service precipitation forecasts, accumulated precipitation in the Potomac watershed above Little Falls is expected to be less than 0.5 inches over the next 10 days. The Middle Atlantic River Forecast Center’s estimate of the past 3-day precipitation is close to 0 inches.
We appreciate your ongoing daily submission of withdrawal, storage, and discharge data through regular emails. Please continue to submit data and ensure it is 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 is not currently on our distribution list, please notify us by emailing coop@icprb.org. And of course, 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:
None
Daily flows:
Little Falls gage flow 2025-09-01: 1150 MGD (1780 cfs)
Little Falls gage flow 2025-09-02: 1086 MGD (est., based on recently available real-time data) (1680 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2025-09-01: 1280 MGD (1980 cfs)
Point of Rocks flow 2025-09-02: 1247 MGD (est., based on recently available real-time data) (1930 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2025-09-01: 1150 MGD (1779 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 (2025-09-01):
Fairfax Water Corbalis withdrawal - Potomac: 129 MGD
WSSC Water Potomac withdrawal: 154 MGD
Washington Aqueduct withdrawal - Great Falls: 138 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 434 MGD
Total net Potomac withdrawal: 427 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1980 cfs
QPR, obs: 1980 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.