Overall Runoff For September Above Average
Although overall runoff for September 2025 in the upper Missouri River Basin was above average, runoff in the Fort Peck and Garrison reaches continues to be well-below average.
“Beneficial rainfall occurred over central South Dakota and North Dakota in September resulting in wellabove average runoff into Oahe, Big Bend, Fort Randall and Gavins Point,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.
“The above-average runoff combined with the lower releases from Gavins Point slightly improves the System storage outlook for the beginning of the 2026 runoff season,” Remus added.
September runoff was 1.3 million acre-feet, 109 percent of average above Sioux City. Upper Basin contributions from Garrison Dam to Sioux City, Iowa, made up 72 percent of the September runoff, while the reaches above Garrison Dam contributed 28 percent of the runoff.
By comparison, the Fort Peck and Garrison reaches normally contribute about 65 percent of September’s upper Basin runoff. Upper Basin runoff for October is forecast to be about 75 percent of average, due to ongoing below-average forecasts in the Fort Peck and Garrison reaches. The updated 2025 calendar year forecast for the upper Basin is 19.6 MAF, 76 percent of average. Average annual runoff for the upper Basin is 25.7 MAF.
As of Oct. 1, the total volume of water stored in the system was 50.4 MAF, which is 5.7 MAF below the base of the System’s flood control zone. System storage will continue to decline through the fall. The updated reservoir studies indicate that the system storage is expected to be 48.5 MAF at the start of the 2026 runoff season, approximately 7.6 MAF below the base of flood control.
Winter Release Rate
As per the criteria in the Master Manual, the winter release rate is determined based on the Sept. 1 System storage. Per the Sept. 1 System storage, winter releases from Gavins Point Dam will be at least 12,000 cfs. In anticipation of the low winter releases, a letter was sent to water users downstream of Gavins Point Dam making them aware of the planned releases and encouraging them to assess the risk to their facilities.
Draft Annual Operating Plan On Sept. 30, the draft 2025-2026 Annual Operating Plan was posted online at: https://go.mil/mr-meetings. The comment period on the draft AOP will close on Nov. 26.
Public Meetings
The Northwestern Division is planning to host a series of public meetings Oct. 27, Nov. 3 and 4, subject to the availability of funds. Specific dates, times and locations are listed below and can be found on the website at https:// go.mil/mr-meetings.
Monday, Nov. 3 - Bismarck, N.D.: Start time: 1 p.m. CT. Bismarck State College, NECE Bldg. 15, Bavendick Stateroom, 1200 Schafer Street, Bismarck, N.D. 58501 Hydropower
The six mainstem power plants generated 637 million kWh of electricity in September. Typical energy generation for September is 900 million kWh. The power plants are projected to generate 7.7 billion kWh of electricity this year, compared to the long-term average of 9.4 billion kWh.
To view the detailed threeweek release forecast for the mainstem dams, go to https:// go.mil/mr-3wk-fcast.
