Situational Awareness (Tuesday, 2024-07-16)
Trace amounts of rain are predicted over the next 24 hours according to the Middle Atlantic River Forecast Center. Rainfall is expected over the next 3 days, ranging from 0.25 inches in the western portion of the basin to over an inch possible in the DC metro area.
Special conditions:
A contractor will be performing diving inspections of the upstream side of historic Potomac Dam No. 4 in Washington County, MD, on Tuesday, July 16, 2024 and Wednesday, July 17, at Potomac Dam No. 5. During this time, the hydroelectric operator will be diverting water off of the run-of-river dam crest through the powerplant turbines. Efforts are being made to ease the water on and off slowly to minimize downstream flow disruptions.
Daily flows:
Little Falls gage flow 2024-07-15: 879 MGD (1360 cfs)
Little Falls gage flow 2024-07-16: 1118 MGD (est., based on recently available real-time data) (1730 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2024-07-15: 1028 MGD (1590 cfs)
Point of Rocks flow 2024-07-16: 995 MGD (est., based on recently available real-time data) (1540 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2024-07-15: 1043 MGD (1614 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 (2024-07-15):
Fairfax Water Corbalis withdrawal - Potomac: 138 MGD
WSSC Water Potomac withdrawal: 113 MGD
Washington Aqueduct withdrawal - Great Falls: 0 MGD
Washington Aqueduct withdrawal - Little Falls: 164 MGD
Loudoun Water withdrawal: 14 MGD
Loudoun Water Broad Run discharge: 5 MGD
Total Potomac withdrawal: 429 MGD
Total net Potomac withdrawal: 424 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1590 cfs
QPR, obs: 1590 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.