Situational Awareness (Wednesday, 2023-11-01)
About 0.2 inches of rain fell in the Potomac basin over the past several days. According to the Middle Atlantic River Forecast Center predictions, no appreciable rainfall is expected over the next 3 days. The week-long outlook expects a total of approximately 0.5 inches of rain in the basin.
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: 0.19 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.21 (inches)
Daily flows:
Little Falls gage flow 2023-10-31: 704 MGD (1090 cfs)
Little Falls gage flow 2023-11-01: 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 2023-10-31: 763 MGD (1180 cfs)
Point of Rocks flow 2023-11-01: 750 MGD (est., based on recently available real-time data) (1160 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2023-10-31: 704 MGD (1089 cfs)
Note: Estimated as gage flow at Little Falls plus Little Falls water supply withdrawal.
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-10-31):
Fairfax Water Corbalis withdrawal - Potomac: 83 MGD
WSSC Water Potomac withdrawal: 134 MGD
Washington Aqueduct withdrawal - Great Falls: 111 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 333 MGD
Total net Potomac withdrawal: 326 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1180 cfs
QPR, obs: 1180 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.