Flow in the Potomac River at Point of Rocks continues to be close to the 2000 cfs threshold for CO-OP daily monitoring. Average precipitation yesterday in the watershed above Little Falls was 0.28 inches. The Middle Atlantic River Forecast Center’s cumulative forecast for the watershed over the next 3 days is just 0.01 to 0.10 inches.
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: 0.28 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.4 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.48 (inches)
Daily flows:
Little Falls gage flow 2023-07-28: 1234 MGD (1910 cfs)
Little Falls gage flow 2023-07-29: 1260 MGD (est., based on recently available real-time data) (1950 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-07-28: 1370 MGD (2120 cfs)
Point of Rocks flow 2023-07-29: 1234 MGD (est., based on recently available real-time data) (1910 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-07-28):
Fairfax Water Corbalis withdrawal (Potomac): 122 MGD
WSSC Water Potomac withdrawal: 134 MGD
Washington Aqueduct withdrawal: 165 MGD
Loudoun Water withdrawal: 14 MGD
Loudoun Water Broad Run discharge: 5 MGD
Total Potomac withdrawal: 435 MGD
Total net Potomac withdrawal: 430 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 2120 cfs
QPR, obs: 2120 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.