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 (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.

Daily Potomac flow and demand update (Wednesday 2019-09-25)

Submitted by admin1 on Wed, 09/25/2019 - 09:00

Dry conditions persist, with negligible precipitation in the Potomac basin over the past several days. The National Weather Service's forecast calls for little rain over the next 7 days.

Daily Flows:
Little Falls gage flow 2019-09-24: 1053 MGD (1630 cfs)
Little Falls gage flow 2019-09-25: 1034 MGD (est., based on recently available real time data) (1600 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.

Daily Potomac flow and demand update (Tuesday 2019-09-24)

Submitted by admin1 on Tue, 09/24/2019 - 09:00

The Potomac remains dry with 2.8 inches below normal basin average precipitation over the past 30 days. The Middle Atlantic River Forecast Center's 24 and 72 hour precipitation forecast shows 0 to 0.1 inch of precipitation over isolated parts of the basin. The 7-day total precipitation forecast shows 0 to 0.1 inch of precipitation over most of the basin.

Initiated Monitoring - Daily Potomac flow and demand update (Monday 2019-09-23)

Submitted by admin1 on Mon, 09/23/2019 - 09:00

Potomac River flow at Point of Rocks has dropped below the low-flow threshold of 2,000 cfs. Today CO-OP is initiating daily monitoring and reporting of Potomac flows and withdrawals. Today's report appears below.

Conditions have been dry throughout the basin over the past couple of months. National Weather Service precipitation estimates indicate that the basin received no appreciable rain over the past 7 days, and forecasts call for little rain over the next seven days.

​​Discontinue Monitoring - Daily Potomac flow and demand update (Monday 2017-10-30)

Submitted by admin1 on Mon, 10/30/2017 - 09:00

The National Weather Service (NWS) 24 hour observed precipitation shows that there was between 0.10 and 3.00 inches of precipitation in the Potomac basin above Little Falls. The NWS 3-day and 5-day forecasts both predict 0.00 to 0.25 inches of rain in this same area.

Daily Potomac flow and demand update (Sunday 2017-10-29)

Submitted by admin1 on Sun, 10/29/2017 - 09:00

According to the Middle Atlantic River Forecast Center (MARFC), portions of the basin received no rain or trace amounts over the last 24 hours, and the northwestern edge of the basin received up to 2 inches. Over the next day, MARFC predicts 1 to 1 3/4 inches in the drainage area above Little Falls dam. Although flow at the US Geological Survey gage at Point of Rocks is currently above 2,000 cfs, our trigger for daily monitoring, we will continue daily monitoring efforts until we see that flows have significantly improved for several days.

Daily Potomac flow and demand update (Saturday 2017-10-28)

Submitted by admin1 on Sat, 10/28/2017 - 09:00

The National Weather Service (NWS) reports that there was no precipitation in the Potomac basin over the last 24 hours. The NWS 3-day forecast predicts 1.25 to 2.0 inches of rain in the portion of the basin above Little Falls dam. Although flows at the US Geological Survey gage at Point of Rocks is currently above 2,000 cfs, our trigger for daily monitoring, we will continue daily monitoring efforts until we see that flows have significantly improved for several days.

Daily Potomac flow and demand update (Friday 2017-10-27)

Submitted by admin1 on Fri, 10/27/2017 - 09:00

The National Weather Service (NWS) 24 hour observed precipitation shows that there were scattered, trace amounts of rain in the Potomac basin above Little Falls. The NWS 3-day forecast predicts 0.75 to 1.5 inches of rain in this same area. The National Weather Service (NWS) 5-day forecast predicts accumulations of up to 2.5 inches of rain in the Potomac basin.

Daily Potomac flow and demand update (Thursday 2017-10-26)

Submitted by admin1 on Thu, 10/26/2017 - 09:00

The National Weather Service (NWS) 24 hour observed precipitation shows that there were scattered, trace amounts of rain in the Potomac basin above Little Falls. The NWS 3-day forecast predicts 0 to 0.5 inches of rain in this same area with the largest amounts expected in the western portions of the basin. The National Weather Service (NWS) 5-day forecast predicts accumulations of up to 1.75 inches of rain in the Potomac basin.

Daily Potomac flow and demand update (Wednesday 2017-10-25)

Submitted by admin1 on Wed, 10/25/2017 - 09:00

The National Weather Service (NWS) 24 hour observed precipitation shows that there was 0.00 to 0.50 inches of rain in the Potomac basin above Little Falls. The NWS 3-day forecast predicts no rain over the majority of this same area. The US Geological Survey shows that Point of Rocks flow fell below and then rose above 2,000 cfs, our trigger for daily monitoring. We will continue daily monitoring efforts until we see that flows have significantly improved for several days.