Daily Potomac flow and demand update (Wednesday, 2023-09-13)

Situational Awareness (Wednesday, 2023-09-13)
River flows at both the Point of Rocks and Little Falls gages are now above all CO-OP drought monitoring and drought operations thresholds. We are continuing daily drought monitoring because flows are expected to begin falling in the coming week. According to the Middle Atlantic River Forecast Center predictions, only 0.2 inches of rainfall is expected in the basin over the next 7 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: 0.05 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.5 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 1.7 (inches)

Daily flows:
Little Falls gage flow 2023-09-12: 1041 MGD (1610 cfs)
Little Falls gage flow 2023-09-13: 1474 MGD (est., based on recently available real-time data) (2280 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-09-12: 1325 MGD (2050 cfs)
Point of Rocks flow 2023-09-13: 1474 MGD (est., based on recently available real-time data) (2280 cfs)

Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-09-12):
Fairfax Water Corbalis withdrawal - Potomac: 104 MGD
WSSC Water Potomac withdrawal: 127 MGD
Washington Aqueduct withdrawal - Great Falls: 160 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 395 MGD
Total net Potomac withdrawal: 389 MGD

Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 2050 cfs
QPR, obs: 2050 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.