Daily Potomac flow and demand update (Tuesday, 2023-08-01)

Potomac River flows continue to hold relatively steady. Less than an inch of precipitation is in the cumulative forecast for the basin over the next ten 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: 0.14 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.23 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.66 (inches)

Daily flows:
Little Falls gage flow 2023-07-31: 1002 MGD (1550 cfs)
Little Falls gage flow 2023-08-01: 1021 MGD (est., based on recently available real-time data) (1580 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-07-31: 1338 MGD (2070 cfs)
Point of Rocks flow 2023-08-01: 1125 MGD (est., based on recently available real-time data) (1740 cfs)

Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-07-31):
Fairfax Water Corbalis withdrawal (Potomac): 103 MGD
WSSC Water Potomac withdrawal: 113 MGD
Washington Aqueduct withdrawal: 144 MGD
Loudoun Water withdrawal: 15 MGD
Loudoun Water Broad Run discharge: 5 MGD
Total Potomac withdrawal: 375 MGD
Total net Potomac withdrawal: 370 MGD

Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 2070 cfs
QPR, obs: 2070 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.