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 (Tuesday, 2022-11-01)

Submitted by admin1 on Tue, 11/01/2022 - 13:08

Most parts of the Potomac basin above Little Falls received 1/10 to ½ inch of rain yesterday. River flows are already responding. However, the forecast is for dry conditions over the next 7 days, so we expect this slight increase in flows to be short-lived.

Daily flows:
Little Falls gage flow 2022-10-31: 1196 MGD (1850 cfs)
Little Falls gage flow 2022-11-01: 1209 MGD (est., based on recently available real-time data) (1870 cfs)

Daily Potomac flow and demand update (Monday, 2022-10-31)

Submitted by admin1 on Mon, 10/31/2022 - 12:10

Over the past day, 0 to 0.1 inches of precipitation occurred in the Potomac basin above Little Falls; the majority occurred in the North Branch. According to the MARFC’s 72-hour forecast, total rainfall in the basin will range from 0.01 to 0.5 inches over the next three days, with more rain occurring in the southeastern portions (including the DC area) than in the northwestern parts.

Daily Potomac flow and demand update (Sunday, 2022-10-30)

Submitted by admin1 on Sun, 10/30/2022 - 11:56

Daily Potomac flow and demand update (Sunday, 2022-10-30)
Over the past day, no significant rainfall occurred in the Potomac basin above Little Falls. According to the MARFC’s 72-hour forecast, total precipitation in the basin will range from 0.01 to 0.25 inches over the next three days, with more rain occurring in the southeastern portions (including the DC area) than in the northwestern portions.

Daily Potomac flow and demand update (Saturday, 2022-10-29)

Submitted by admin1 on Sat, 10/29/2022 - 12:35

No significant rainfall occurred in the Potomac basin above Little Falls over the past day. According to the MARFC’s 72-hour forecast, total precipitation in the basin will range from 0.01 to 0.25 inches over the next three days, with more rain occurring in the southeastern portions of the basin (including the DC area) than in the northwestern portions.

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

Daily Potomac flow and demand update (Friday, 2022-10-28)

Submitted by admin1 on Sat, 10/29/2022 - 12:32

Stream flows in the Potomac basin continue to slowly decline. According to the National Weather Service’s 7-day cumulative precipitation forecast, little rain is expected over the next week. There was a data gap in real-time flow at the USGS’s Point of Rocks gage yesterday, so yesterday’s daily average flow is estimated

Daily Potomac flow and demand update (Thursday, 2022-10-27)

Submitted by admin1 on Thu, 10/27/2022 - 12:46

According to Middle Atlantic River Forecast Center (MARFC) map products, there was 0.01 to 0.27 inches of rain in the basin over the past 24 hours. The LFFS average basin precipitation is 0.12 inches. MARFC predicts no rainfall over the next three days, although 0.25-0.75 inches of rain is expected in the 5 and 7-day forecasts.

Yesterday, WSSC Water temporarily provided all of the City of Rockville's water. WSSC Water is no longer serving them.

Daily Potomac flow and demand update (Tuesday, 2022-10-25)

Submitted by admin1 on Tue, 10/25/2022 - 09:00

According to Middle Atlantic River Forecast Center (MARFC) map products, there was no significant precipitation in the basin over the past 24 hours. The basin has been dry over the past three days, with the exception of the Monocacy sub-basin, which received up to ½ inch of rain. MARFC predicts accumulations of  trace amounts to ¼ inch over the next three days.