Situational Awareness (Thursday, 2023-10-12)
Potomac River flows are again slowly declining. Total Washington metropolitan area withdrawals are now lower due to the arrival of autumn weather. According to Middle Atlantic River Forecast Center forecasts, up to an inch of rain is expected in the basin over the next three 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 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.06 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.54 (inches)
Daily flows:
Little Falls gage flow 2023-10-11: 924 MGD (1430 cfs)
Little Falls gage flow 2023-10-12: 827 MGD (est., based on recently available real-time data) (1280 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-10-11: 989 MGD (1530 cfs)
Point of Rocks flow 2023-10-12: 982 MGD (est., based on recently available real-time data) (1520 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-10-11):
Fairfax Water Corbalis withdrawal - Potomac: 90 MGD
WSSC Water Potomac withdrawal: 128 MGD
Washington Aqueduct withdrawal - Great Falls: 60 MGD
Washington Aqueduct withdrawal - Little Falls: 79 MGD
Loudoun Water withdrawal: 9 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 367 MGD
Total net Potomac withdrawal: 361 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1530 cfs
QPR, obs: 1530 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.