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.

Daily Potomac flow and demand update (Saturday 2019-10-05)

Submitted by admin1 on Sat, 10/05/2019 - 09:00

According to Middle Atlantic River Forecast Center estimates, no rain fell in the basin over the past 24 hours. Between 0.01 and 1.25 inches of rain is forecast over the next 7 days.

The USACE's recreational release has passed the Point of Rocks gage and flows at that gage have dropped below 2000 cfs again. MARFC's GEFS predictions are suggesting that some of the precipitation forecast may affect the Point of Rocks gage flow between October 7 and 11, causing flows at that gage to increase slightly.

REVISION Recent basin-wide average precipitation (above Little Falls):

Daily Potomac flow and demand update (Friday 2019-10-04)

Submitted by admin1 on Fri, 10/04/2019 - 09:00

Adams County, PA, and nearby areas saw some rain yesterday. According to the Middle Atlantic River Forecast Center, accumulations of up to 1/10 inches are expected in the far northern portion of the Potomac basin over the next 3 days, primarily in Pennsylvania. The 7-day forecast is not as promising as it was a few days ago, but accumulations of 1/4 to 3/4 inches are expected throughout most of the basin, mostly occurring Sunday through Tuesday.

Daily Potomac flow and demand update (Thursday 2019-10-03)

Submitted by admin1 on Thu, 10/03/2019 - 09:00

Trace amounts of rain fell over some northern areas of the basin over the past 24 hours according to the Middle Atlantic River Forecast Center. Forecasts are calling for 0.5 to 1.5 inches of rainfall across much of the basin over the next 7 days.

REVISION 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)

Daily Potomac flow and demand update (Wednesday 2019-10-02)

Submitted by admin1 on Wed, 10/02/2019 - 09:00

According to Middle Atlantic River Forecast Center estimates, no rain fell in the basin in the past 24 hours. However, streamflows have risen slightly due to Monday's rain, and forecasts call for over an inch and a half of rain throughout most of the basin over the next 7 days.

REVISION 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)

Daily Potomac flow and demand update (Monday 2019-09-30)

Submitted by admin1 on Mon, 09/30/2019 - 09:00

There was no rain in most of the Potomac basin over the past 24 hours, but according to Middle Atlantic River Forecast Center (MARFC) estimates, 0.25 to 0.50 inches of rain fell in a few isolated locations in the western part of the basin yesterday. Forecasts call for the dry conditions to continue, but the MARFC predicts precipitation accumulations of over 0.10 inches in the far western portion of the basin over the next 3 days.

REVISION Recent basin-wide average precipitation (above Little Falls):

Daily Potomac flow and demand update (Thursday 2019-09-26)

Submitted by admin1 on Thu, 09/26/2019 - 09:00

Yesterday brought no relief from the dry conditions in the Potomac basin. The National Weather Service forecasts negligible accumulations of precipitation over the next 7 days.

Daily Flows:
Little Falls gage flow 2019-09-25: 1060 MGD (1640 cfs)
Little Falls gage flow 2019-09-26: 1034 MGD (est., based on recently available real time data) (1600 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.