Today, CO-OP is initiating daily drought monitoring because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below CO-OP's daily monitoring trigger of 2000 cfs. According to National Weather Service's (NWS) quantitative precipitation forecasts, a little over a 1/10 of an inch of rain is expected in the basin over the next 3 days.
Thank you all for your ongoing successful submission of necessary data through regular emails! Please continue to keep up with those submissions on a daily basis and make sure the data is sent by 8:00 am for the duration of this period of drought monitoring. If you have any questions, please contact us via coop@icprb.org.
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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: 0.1 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.11 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.18 (inches)
Daily flows:
Little Falls gage flow 2021-07-26: 1629 MGD (2520 cfs)
Little Falls gage flow 2021-07-27: 1583 MGD (est., based on recently available real time data) (2450 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2021-07-26: 1299 MGD (2010 cfs)
Point of Rocks flow 2021-07-27: 1267 MGD (est., based on recently available real time data) (1960 cfs)
Yesterday's Washington metropolitan are Potomac River withdrawals and discharges (2021-07-26):
Fairfax Water Corbalis withdrawal (Potomac): 148 MGD
WSSC Water Potomac withdrawal: 129 MGD
Washington Aqueduct withdrawal: 150 MGD
Loudoun Water withdrawal: 11 MGD
Loudoun Water Broad Run discharge: 3 MGD
Total Potomac withdrawal: 438 MGD
Total Potomac withdrawal: 435 MGD
Loudoun Water drought operations protocol river flow values (2021-07-27):
QPR: 2010 cfs
QPR, obs: 2010 cfs
QPR, WS: 0 cfs
Note to Loudoun Water: All NWS ensemble flow forecasts (HEFS, GEFS, NAEFS) for Point of Rocks are above 1400 cfs for the next 7 days – see https://www.weather.gov/erh/mmefs_marfc?id=PORM2&model=NAEFS.