Monitoring Reports

During periods of drought, the Cooperative Water Supply Operations on the Potomac (CO-OP) helps manage the Washington metropolitan area water supply system by coordinating withdrawals from the Potomac River and off-river reservoirs and recommending releases from upstream reservoirs when forecasted flow in the river is not sufficient to meet expected needs. These needs include water demands and an environmental flow-by of 100 million gallons per day (MGD) on the Potomac River at Little Falls dam near Washington, D.C.

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Daily Potomac flow and demand update (Tuesday 2021-08-10)

Scattered locations across the upper Potomac Basin received between 0.1 and 0.5 inches of rain over the past 24 hours. Small portions of the basin near Washington D.C received up to 2 inches of rain. 0.1 to 1.5 inches of rain are expected over the next 3 days.
Adjustments made yesterday to the Little Falls gage’s rating curve resulted in discharge values lower than previously reported.

Daily Potomac flow and demand update (Monday 2021-08-09)

Flows continued to fall over the weekend. Yesterday there were scattered amounts of precipitation in the North Branch of the Potomac basin. In the next 3 days, the basin may receive between a tenth of an inch to one inch of precipitation depending on location.Thank you for participating in weekend data submissions.

Daily Potomac flow and demand update (Sunday 2021-08-08)

Widely scattered locations across the upper basin received trace amounts of rain (up to 0.1 inches) over the past 24 hours. Precipitation totaling 0.01 to 0.25 inches is expected in the upper basin over the next three days. Higher amounts of half an inch are also possible in scattered locations in Pennsylvania and along the Virginia-West Virginia border. Flow at Point of Rocks is holding steady above 1500 cfs.

Daily Potomac flow and demand update (Saturday 2021-08-07)

The Potomac basin upstream of Little Falls dam received no significant precipitation over the past 24 hours. The forecast for the next 3 days is 0.01 to 0.10 inches throughout much of the basin, though up to 0.50 inches is expected in the southeastern portion of the basin, including in the Washington, DC, metropolitan area.

Daily Potomac flow and demand update (Friday 2021-08-06)

Less than a quarter inch of rain fell in portions of the upper basin over the past 24 hours. Scattered locations with higher precipitation amounts of up to one inch also occurred. Trace amounts, up to 0.1 inches, of rain are expected over the next three days. Flows remain steady above 1,500 cfs.

Daily Potomac flow and demand update (Thursday 2021-08-05)

River flow continues to slowly decline. There was no appreciable precipitation in the Potomac basin over the past 24 hours. An average basin-wide accumulation of less than 1/10 of an inch is expected over the next three days.

Daily Potomac flow and demand update (Wednesday 2021-08-04)

No appreciable rain fell in the basin over the past 24 hours. A trace amount, up to 0.1 inches, is expected over the next three days.

Daily flows:
Little Falls gage flow 2021-08-03: 1286 MGD (2390 cfs)
Little Falls gage flow 2021-08-04: 1195 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 2021-08-03: 904 MGD (1680 cfs)
Point of Rocks flow 2021-08-04: 893 MGD (est., based on recently available real time data) (1660 cfs)

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