Situational Awareness (Monday, 2024-11-11)
Over the past 24 hours, approximately 0.2 inches of rain fell across the basin. According to the Middle Atlantic River Forecast Center predictions, the next 72 hours may see 0.2 inches of rain. The week-long outlook expects a total of approximately 0.3 inches of rain in the basin.
Special Conditions
None
Recent basin-wide average precipitation (above Little Falls):
(based on CO-OP's Low Flow Forecast System analysis of Middle Atlantic River Forecast Center (MARFC) gridded multisensor precipitation estimates)
Yesterday's area-weighted average basin precipitation: 0.21 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.21 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.23 (inches)
Daily flows:
Little Falls gage flow 2024-11-10: 1138 MGD (1760 cfs)
Little Falls gage flow 2024-11-11: 1170 MGD (est., based on recently available real-time data) (1810 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2024-11-10: 1131 MGD (1750 cfs)
Point of Rocks flow 2024-11-11: 1163 MGD (est., based on recently available real-time data) (1800 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2024-11-10: 1173 MGD (1815 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 (2024-11-10):
Fairfax Water Corbalis withdrawal - Potomac: 90 MGD
WSSC Water Potomac withdrawal: 140 MGD
Washington Aqueduct withdrawal - Great Falls: 82 MGD
Washington Aqueduct withdrawal - Little Falls: 35 MGD
Loudoun Water withdrawal: 10 MGD
Loudoun Water Broad Run discharge: 8 MGD
Total Potomac withdrawal: 356 MGD
Total net Potomac withdrawal: 349 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1750 cfs
QPR, obs: 1750 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.