Situational Awareness (Tuesday, 2023-10-17)
Potomac River flows are rising due to this past weekend’s rainfall, but flows at Point of Rocks are not expected to rise above the 2000 cfs drought monitoring threshold for any extended period of time. According to Middle Atlantic River Forecast Center predictions, only approximately ¼ inch of rain 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 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.76 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.76 (inches)
Daily flows:
Little Falls gage flow 2023-10-16: 937 MGD (1450 cfs)
Little Falls gage flow 2023-10-17: 924 MGD (est., based on recently available real-time data) (1430 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-10-16: 976 MGD (1510 cfs)
Point of Rocks flow 2023-10-17: 1202 MGD (est., based on recently available real-time data) (1860 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-10-16):
Fairfax Water Corbalis withdrawal - Potomac: 81 MGD
WSSC Water Potomac withdrawal: 108 MGD
Washington Aqueduct withdrawal - Great Falls: 41 MGD
Washington Aqueduct withdrawal - Little Falls: 64 MGD
Loudoun Water withdrawal: 5 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 299 MGD
Total net Potomac withdrawal: 294 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1510 cfs
QPR, obs: 1510 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.