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 (Wednesday, 2023-09-13)

Submitted by admin1 on Wed, 09/13/2023 - 12:24

Situational Awareness (Wednesday, 2023-09-13)
River flows at both the Point of Rocks and Little Falls gages are now above all CO-OP drought monitoring and drought operations thresholds. We are continuing daily drought monitoring because flows are expected to begin falling in the coming week. According to the Middle Atlantic River Forecast Center predictions, only 0.2 inches of rainfall is expected in the basin over the next 7 days.

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

Daily Potomac flow and demand update (Tuesday, 2023-09-12)

Submitted by admin1 on Tue, 09/12/2023 - 08:58

Flow at Point of Rocks has reached 2000 cfs. According to the Middle Atlantic River Forecast Center predictions, the next three days may see 0.3 inches of rain.  

The Washington Aqueduct suspended voluntary load shift (withdrawal) at Little Falls yesterday. They are currently withdrawing 100% from the Great Falls intake.

SUSPENDING DROUGHT OPERATIONS - Morning Potomac flow and demand update (Monday, 2023-09-11)

Submitted by admin1 on Mon, 09/11/2023 - 12:24

CO-OP is suspending drought operations because flow at the US Geological Survey’s gage at Little Falls, Maryland, has risen well above the drought operations threshold and is approaching median flows. We will continue sending daily morning updates on conditions while flow at Point of Rocks remains below 2,000 cfs. According to the Middle Atlantic River Forecast Center predictions, the next 24 hours may see 0.3 inches of rain. Over the next three days, the average basin rainfall may be around 0.6 inches.

Morning Potomac flow and demand update (Sunday, 2023-09-10)

Submitted by snummer on Sun, 09/10/2023 - 13:05

Local rainfall has elevated river flow at Little Falls. Flows at Little Falls are now well above the numerical threshold for the Low Flow Allocation Agreement (LFAA) Alert stage. 

CO-OP staff will be monitoring flows at upstream gages to better assess the impact of recent rainfall on basin flows. 

According to the Middle Atlantic River Forecast Center predictions, the next 24 hours may see 0.4 inches of rain. Over the next 3 days, the average basin rainfall may be around 0.8 inches. The week-long outlook expects a total of approximately 1 inches of rain in the basin.

Morning Potomac flow and demand update (Saturday, 2023-09-09)

Submitted by admin1 on Sat, 09/09/2023 - 08:45

With the recent rain, river flow at Little Falls has risen to 1550 cfs. According to the Middle Atlantic River Forecast Center predictions, the next 72 hours may see 0.9 inches of rain. The week-long outlook expects a total of approximately 1.5 inches of rain in the basin.

The proactive voluntary load shift from Great Falls to Little Falls by Washington Aqueduct is still ongoing.  

Afternoon Potomac flow and demand update (Friday, 2023-09-08)

Submitted by snummer on Fri, 09/08/2023 - 17:26

Flows at the Little Falls gauge have risen over the past 12 hours, likely in response to the rain that occurred in some parts of the basin yesterday. 

Please remember to begin sending a supplemental email each morning by 7:30 am with predicted total and off Potomac withdrawals (in MGD) for today and tomorrow. Thank you for your continued cooperation.  

The proactive voluntary load shift from Great Falls to Little Falls by Washington Aqueduct is still ongoing. 

Morning Potomac flow and demand update (Friday, 2023-09-08)

Submitted by snummer on Fri, 09/08/2023 - 17:04

According to Middle Atlantic River Forecast Center predictions, the next three days may see approximately 1.5 inches of rainfall. 

ICPRB continues to work to improve projected demands and incorporate supplier projections. In an effort to provide the most robust projections possible, we will be contacting suppliers and asking them to begin sending a supplemental email each morning with predicted total and off Potomac withdrawals (in MGD) for today and tomorrow.

The proactive voluntary load shift from Great Falls to Little Falls by Washington Aqueduct is still ongoing.  

Afternoon Potomac flow and demand update (Saturday, 2023-09-02)

Submitted by admin1 on Fri, 09/08/2023 - 13:09

We expect Potomac River flows to start slowly declining over the remainder of the holiday weekend. No significant precipitation is predicted to fall in the basin over the next five days.

Daily flows:
Little Falls gage flow 2023-09-01: 457 MGD (707 cfs)
Little Falls gage flow 2023-09-02: 487 MGD (est., based on recently available real-time data) (753 cfs)
Note: Gage flow at Little Falls is measured after water supply withdrawals.
Point of Rocks flow 2023-09-01: 821 MGD (1270 cfs)