Situational Awareness (Monday, 2023-10-30)
Small amounts of rain fell in the Potomac basin during the past several days, averaging about 0.1 inches. Accumulations of only about 0.1 inches are forecasted over the next week. Potomac River flows continue to slowly decline.
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: 0.09 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.11 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.11 (inches)
Daily flows:
Little Falls gage flow 2023-10-29: 795 MGD (1230 cfs)
Little Falls gage flow 2023-10-30: 737 MGD (est., based on recently available real-time data) (1140 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-10-29: 717 MGD (1110 cfs)
Point of Rocks flow 2023-10-30: 776 MGD (est., based on recently available real-time data) (1200 cfs)
Yesterday's estimated daily flows:
Great Falls estimated flow 2023-10-29: 795 MGD (1230 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 (2023-10-29):
Fairfax Water Corbalis withdrawal - Potomac: 90 MGD
WSSC Water Potomac withdrawal: 132 MGD
Washington Aqueduct withdrawal - Great Falls: 118 MGD
Washington Aqueduct withdrawal - Little Falls: 0 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 345 MGD
Total net Potomac withdrawal: 339 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1110 cfs
QPR, obs: 1110 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.