Situational Awareness (Monday, 2023-10-09)
The Potomac River watershed above Little Falls received about a ½ inch of rain during the past three days, and as a result river flows have increased slightly. The precipitation outlook for the next seven days is promising – about an inch of rain is expected.
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: 0.48 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.48 (inches)
Daily flows:
Little Falls gage flow 2023-10-08: 989 MGD (1530 cfs)
Little Falls gage flow 2023-10-09: 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 2023-10-08: 950 MGD (1470 cfs)
Point of Rocks flow 2023-10-09: 995 MGD (est., based on recently available real-time data) (1540 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-10-08):
Fairfax Water Corbalis withdrawal - Potomac: 79 MGD
WSSC Water Potomac withdrawal: 131 MGD
Washington Aqueduct withdrawal - Great Falls: 85 MGD
Washington Aqueduct withdrawal - Little Falls: 52 MGD
Loudoun Water withdrawal: 10 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 357 MGD
Total net Potomac withdrawal: 350 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1470 cfs
QPR, obs: 1470 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.