Situational Awareness (Thursday, 2024-07-11)
Scattered thunderstorms occurred throughout the basin over the past 24 hours. Over the next 3 days, 0.1 to 0.5 inches of rain are expected, mainly in the eastern parts of the basin.
Special Conditions
The effects of the whitewater release from Savage Reservoir last Sunday (2024-07-07) are currently visible at the USGS streamflow gage on the Potomac River at Shepherdstown.
Daily flows:
Little Falls gage flow 2024-07-10: 898 MGD (1390 cfs)
Little Falls gage flow 2024-07-11: 1041 MGD (est., based on recently available real-time data) (1610 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2024-07-10: 1150 MGD (1780 cfs)
Point of Rocks flow 2024-07-11: 1138 MGD (est., based on recently available real-time data) (1760 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2024-07-10: 1038 MGD (1606 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 (2024-07-10):
Fairfax Water Corbalis withdrawal - Potomac: 146 MGD
WSSC Water Potomac withdrawal: 162 MGD
Washington Aqueduct withdrawal - Great Falls: 0 MGD
Washington Aqueduct withdrawal - Little Falls: 140 MGD
Loudoun Water withdrawal: 14 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 462 MGD
Total net Potomac withdrawal: 456 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1780 cfs
QPR, obs: 1780 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.