Daily Potomac flow and demand update (Tuesday, 2023-09-12)

Submitted by admin1 on Tue, 09/12/2023 - 08:58

Flow at Point of Rocks has reached 2000 cfs. According to the Middle Atlantic River Forecast Center predictions, the next three days may see 0.3 inches of rain.  

The Washington Aqueduct suspended voluntary load shift (withdrawal) at Little Falls yesterday. They are currently withdrawing 100% from the Great Falls intake.

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: 0.23 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 1.05 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 1.65 (inches)

Daily flows:
Little Falls gage flow 2023-09-11: 1512 MGD (2340 cfs)
Little Falls gage flow 2023-09-12: 1028 MGD (est., based on recently available real-time data) (1590 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-09-11: 911 MGD (1410 cfs)
Point of Rocks flow 2023-09-12: 1293 MGD (est., based on recently available real-time data) (2000 cfs)

Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-09-11):
Fairfax Water Corbalis withdrawal - Potomac: 96 MGD
WSSC Water Potomac withdrawal: 126 MGD
Washington Aqueduct withdrawal - Great Falls: 98 MGD
Washington Aqueduct withdrawal - Little Falls: 53 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 378 MGD
Total net Potomac withdrawal: 372 MGD

Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1410 cfs
QPR, obs: 1410 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 – see https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS.

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.

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