Situational Awareness (Wednesday, 2023-11-08)
Dry conditions persist. Though fluctuations occur, river flows overall are continuing to slowly fall. No rain fell in the basin during the past three days, and little rain is expected over the coming week – only about 0.2 inches.
Special notices: The National Park Service contractor conducted a bathymetric survey at Potomac Dam No. 5 beginning on November 7. This has caused an intra-daily flow fluctuation that can be observed downstream in the Shepherdstown gage hydrograph. The fluctuation is now also partially visible at Point of Rocks. See graph below. ICPRB staff will be analyzing the likely impact on flows at Little Falls in the coming days.
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 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.02 (inches)
Daily flows:
Little Falls gage flow 2023-11-07: 579 MGD (896 cfs)
Little Falls gage flow 2023-11-08: 672 MGD (est., based on recently available real-time data) (1040 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-11-07: 853 MGD (1320 cfs)
Point of Rocks flow 2023-11-08: 1176 MGD (est., based on recently available real-time data) (1820 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2023-11-07: 579 MGD (896 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 (2023-11-07):
Fairfax Water Corbalis withdrawal - Potomac: 71 MGD
WSSC Water Potomac withdrawal: 132 MGD
Washington Aqueduct withdrawal - Great Falls: 115 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 324 MGD
Total net Potomac withdrawal: 317 MGD
Yesterday's Patuxent, Occoquan, and Net Total System Withdrawal (2023-11-07):
FW Occoquan withdrawal: 68 MGD
WSSC Patuxent withdrawal: 30 MGD
Yesterday's total system withdrawal (2023-11-07): 416 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1320 cfs
QPR, obs: 1320 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.