Flow in the river has held fairly steady over the past several days, at around 1800 cfs at Point of Rocks, and according to National Weather Service forecasts this will continue to be the case for the upcoming week. No appreciable precipitation fell over the basin during the past 24 hours. The Washington metropolitan area may receive up to an inch of rain over the next 3 days, but much less rain is expected west of the metro area.
Note that there was an error in our reported July 28 Washington Aqueduct Potomac River withdrawal of 131 MGD, brought to our attention by Anne Spiesman. The correct value was 150 MGD.
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 multi-sensor precipitation estimates)
Yesterday's area-weighted average basin precipitation: 0.08 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.34 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.45 (inches)
Daily flows:
Little Falls gage flow 2021-07-30: 1577 MGD (2440 cfs)
Little Falls gage flow 2021-07-31: 1435 MGD (est., based on recently available real time data) (2220 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2021-07-30: 1209 MGD (1870 cfs)
Point of Rocks flow 2021-07-31: 1176 MGD (est., based on recently available real time data) (1820 cfs)
Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2021-07-30):
Fairfax Water Corbalis withdrawal (Potomac): 122 MGD
WSSC Water Potomac withdrawal: 115 MGD
Washington Aqueduct withdrawal: 143 MGD
Loudoun Water withdrawal: 12 MGD
Loudoun Water Broad Run discharge: 4 MGD
Total Potomac withdrawal: 392 MGD
Total net Potomac withdrawal: 388 MGD
Loudoun Water drought operations protocol river flow values (1627733542):
QPR: 1870 cfs
QPR, obs: 1870 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 – https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS.