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, 2023-07-29)

Submitted by admin1 on Sat, 07/29/2023 - 13:03

Flow in the Potomac River at Point of Rocks continues to be close to the 2000 cfs threshold for CO-OP daily monitoring. Average precipitation yesterday in the watershed above Little Falls was 0.28 inches. The Middle Atlantic River Forecast Center’s cumulative forecast for the watershed over the next 3 days is just 0.01 to 0.10 inches.

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

Daily Potomac flow and demand update (Wednesday, 2023-06-14)

Submitted by admin1 on Wed, 06/14/2023 - 12:35

In the last 24 hours, MARFC reports precipitation ranging from 0.01 to 0.25 inches in portions of the Potomac watershed above Little Falls. The forecast for the next three days indicates a potential accumulation of up to 0.25-inch precipitation. (Note this is a correction to the emailed version.)

Despite the river flows at Point of Rocks being above the daily monitoring threshold of 2000 cfs, they remain relatively low for this time of year. Until a significant increase occurs, the CO-OP will continue daily monitoring to closely observe the situation.  

Daily Potomac flow and demand update (Tuesday, 2023-06-13)

Submitted by admin1 on Tue, 06/13/2023 - 12:38

A little under a half inch of rain fell yesterday in Potomac watershed above Little Falls and up to ¼ inch is forecast over the next three days. Average river flow yesterday at Point of Rocks was just 2000 cfs, CO-OP’s threshold for daily monitoring. It’s likely that flows will rise slightly above this level over the next week due to the recent and forecasted rainfall. However, flows are low for this time of year, so CO-OP will continue daily drought monitoring until a significant increase occurs.

Initiation of CO-OP daily drought monitoring and reporting (Monday, 2023-06-12)

Submitted by admin1 on Mon, 06/12/2023 - 14:00

CO-OP is initiating daily drought monitoring and reporting today because Potomac River flow at the US Geological Survey’s gage at Point of Rocks, Maryland, has fallen below 2000 cubic feet per second (cfs), CO-OP's daily monitoring threshold. According to the Middle Atlantic River Forecast Center (MARFC) quantitative precipitation forecasts, cumulative rainfall ranging from 1/10 to 3/4 inch is expected in the basin over the next 3 days. MARFC ensemble forecasts do predict additional rain and rising river flows over the next 10 days.

2022 WMA Drought Exercise-Day 3: Morning Potomac flow and demand update (Thursday, 2022-11-17)

Submitted by hmoltz on Thu, 11/17/2022 - 14:38

This is the final day of the three-day 2022 WMA Drought Exercise. Simulated Potomac River flows at Little Falls have fallen to 104 MGD. Forecasts for today indicate that SIMULATED flows are expected to rise. We requested a SIMULATED Jennings Randolph water supply release this morning of approximately 30 MGD with a Luke target of 297 cfs. Little Seneca continues to make a SIMULATED water supply release to augment flows at Little Falls.

2022 WMA Drought Exercise-Day 2: Afternoon Potomac flow and demand update (Wednesday, 2022-11-16)

Submitted by snummer on Wed, 11/16/2022 - 18:19

No additional operational changes are requested for this afternoon. SIMULATED flows at Little Falls are staying above 150 MGD. 

During yesterday’s practice call, the DCTC recommended entering the SIMULATED Drought Warning Stage of the MWCOG Drought Awareness Response Plan. This discussion occurred because the SIMULATED combined water supply storage in Jennings Randolph and Little Seneca fell below 60%.

Best regards, 
ICPRB CO-OP Drought Team

2022 WMA Drought Exercise-Day 2: Morning Potomac flow and demand update (Wednesday, 2022-11-16)

Submitted by snummer on Wed, 11/16/2022 - 14:18

Welcome to Day 2 of the 2022 WMA Drought Exercise. Simulated Potomac River flows are continuing to fall. We have asked WSSC Water to make a simulated reduction of their Potomac River withdrawals by 7 MGD to help maintain the Little Falls flow-by today. In addition, we have requested a simulated 141-MGD Little Seneca Reservoir release to help maintain the flow-by tomorrow. We estimate that 40 cfs of flow at Point of Rocks yesterday is due to a simulated past water supply release from Jennings Randolph Reservoir as noted in the simulated Loudoun Water drought operations protocol below. 

2022 WMA Drought Exercise - Day 1: Afternoon Potomac flow and demand update (Tuesday, 2022-11-15)

Submitted by admin1 on Tue, 11/15/2022 - 18:24

Following this morning's operations request by ICPRB CO-OP, WSSC Water initiated a SIMULATED water supply release from the Little Seneca Reservoir at 9:30 AM. This reservoir is located in the Black Hill Regional Park. 

In talking with Fairfax Water distribution staff this morning, we learned that the maximum possible SIMULATED load shift today from the Potomac to the Occoquan is 5 MGD due to ACTUAL installation work at the Griffith plant.