Situational Awareness (Friday, 2024-09-20)
According to the Middle Atlantic River Forecast Center predictions, no rain is expected in the next 24 hours. Over the next 3 days, the average basin rainfall is estimated to be around 0.2 inches. The week-long forecast projects a total of approximately 0.8 inches.
Special Conditions
An increase in flow can be observed at the Points of Rocks gage, which is likely due to dam operations.
The whitewater release scheduled for Savage River Dam on Saturday, September 28th, 2024, is canceled due primarily to the extended very dry weather and low flow conditions. Additional information can be found at http://www.nab-wc.usace.army.mil/northBranch.html
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: 0.59 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.59 (inches)
Daily flows:
Little Falls gage flow 2024-09-19: 1190 MGD (1840 cfs)
Little Falls gage flow 2024-09-20: 1008 MGD (est., based on recently available real-time data) (1560 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2024-09-19: 1079 MGD (1670 cfs)
Point of Rocks flow 2024-09-20: 1338 MGD (est., based on recently available real-time data) (2070 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2024-09-19):
Fairfax Water Corbalis withdrawal - Potomac: 106 MGD
WSSC Water Potomac withdrawal: 109 MGD
Washington Aqueduct withdrawal - Great Falls: 106 MGD
Washington Aqueduct withdrawal - Little Falls: 3 MGD
Loudoun Water withdrawal: 10 MGD
Loudoun Water Broad Run discharge: 7 MGD
Total Potomac withdrawal: 334 MGD
Total net Potomac withdrawal: 327 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1670 cfs
QPR, obs: 1670 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.