In the past 24 hours, up to 0.5 inches of rain fell in localized areas of the Potomac Basin, mainly in the northwestern portions and around the Washington D.C area. According to the Middle Atlantic River Forecast Center’s cumulative forecast, no substantial rain is expected in the next 72 hours. River flow at Point of Rocks increased slightly but is still close to the 2000 cfs daily monitoring threshold.
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 (2023-07-30): 0 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.37 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.56 (inches)
Daily flows:
Little Falls gage flow 2023-07-30: 1338 MGD (2070 cfs)
Little Falls gage flow 2023-07-31: 969 MGD (est., based on recently available real-time data) (1500 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-07-30: 1241 MGD (1920 cfs)
Point of Rocks flow 2023-07-31: 1325 MGD (est., based on recently available real-time data) (2050 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2023-07-30):
Fairfax Water Corbalis withdrawal (Potomac): 97 MGD
WSSC Water Potomac withdrawal: 121 MGD
Washington Aqueduct withdrawal: 141 MGD
Loudoun Water withdrawal: 14 MGD
Loudoun Water Broad Run discharge: 4 MGD
Total Potomac withdrawal: 373 MGD
Total net Potomac withdrawal: 369 MGD
Loudoun Water Potomac River (PR) flow values for drought operations protocol (based on yesterday's flows):
QPR: 1920 cfs
QPR, obs: 1920 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.