Situational Awareness (Monday, 2024-07-22)
Trace amounts of rain fell in scattered areas of the basin yesterday. According to the Middle Atlantic River Forecast Center, up to an inch of rain is possible over the next 24 hours. The average basin rainfall for the next 3 days may be around 1.5 inches.
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: 0.01 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.17 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.53 (inches)
Daily flows:
Little Falls gage flow 2024-07-21: 717 MGD (1110 cfs)
Little Falls gage flow 2024-07-22: 606 MGD (est., based on recently available real-time data) (937 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2024-07-21: 885 MGD (1370 cfs)
Point of Rocks flow 2024-07-22: 892 MGD (est., based on recently available real-time data) (1380 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2024-07-21: 758 MGD (1172 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 (2024-07-21):
Fairfax Water Corbalis withdrawal - Potomac: 118 MGD
WSSC Water Potomac withdrawal: 160 MGD
Washington Aqueduct withdrawal - Great Falls: 94 MGD
Washington Aqueduct withdrawal - Little Falls: 41 MGD
Loudoun Water withdrawal: 13 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 424 MGD
Total net Potomac withdrawal: 419 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1370 cfs
QPR, obs: 1370 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.