Initiation of CO-OP daily drought monitoring and reporting (Monday, 2022-10-24)

Submitted by admin1 on Mon, 10/24/2022 - 09:00

CO-OP is initiating daily drought monitoring and reporting today because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below 2000 cubic feet per second (cfs), CO-OP's daily monitoring threshold. According to National Weather Service's (NWS) quantitative precipitation forecasts, less than a 1/10 of an inch of rain is expected in the basin over the next 3 days.

We are in contact with the USGS’s MD-DE-DC Water Science Center, and they plan to collect field data at the Point of Rocks gage this week to verify or update their stage/discharge relationship to take into account any change in channel conditions.

Thank you all for your ongoing successful submission of withdrawal, storage, and discharge 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

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: 0.02 (inches)
Past 3-day cumulative area-weighted average basin precipitation: 0.02 (inches)
Past 7-day cumulative area-weighted average basin precipitation: 0.03 (inches)

Daily flows:
Little Falls gage flow 2022-10-23: 1280 MGD (1980 cfs)
Little Falls gage flow 2022-10-24: 1234 MGD (est., based on recently available real time data) (1910 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2022-10-23: 1293 MGD (2000 cfs)
Point of Rocks flow 2022-10-24: 1280 MGD (est., based on recently available real time data) (1980 cfs)

Yesterday's Washington metropolitan area Potomac River withdrawals and discharges (2022-10-23):
Fairfax Water Corbalis withdrawal (Potomac): 74 MGD
WSSC Water Potomac withdrawal: 121 MGD
Washington Aqueduct withdrawal: 121 MGD
Loudoun Water withdrawal: 13 MGD
Loudoun Water Broad Run discharge: 6 MGD
Total Potomac withdrawal: 330 MGD
Total net Potomac withdrawal: 324 MGD

Loudoun Water drought operations protocol river flow values (based on yesterday's flows):
QPR: 2000 cfs
QPR, obs: 2000 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

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