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 well-above 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% of average above Sioux City. Upper Basin contributions from Garrison Dam to Sioux City, IA made up 72% of the September runoff, while the reaches above Garrison Dam contributed 28% of the runoff. By comparison, the Fort Peck and Garrison reaches normally contribute about 65% of September’s upper Basin runoff. Upper Basin runoff for October is forecast to be about 75% 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% 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.

Navigation

Gavins Point Dam releases are being set to provide navigation flow support at a level 4,500 cfs below full service at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City). Flow targets may be missed to conserve water if there is no commercial navigation in a given reach. The flow support season will end on December 1 at the mouth of the Missouri River.

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. 

Fall 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, Oct. 27 – Smithville, MO

• Start time: 1000 CT
• Jerry Litton Visitor Center
• 16311 DD Hwy
• Smithville, MO 64089

Monday, Oct. 27 – Nebraska City, NE

• Start time: 1600 CT
• Lewis and Clark Interpretive Center
• 100 Valmont Drive
• Nebraska City, NE 68410

Thursday, Oct. 30 – Online Webinar

• Start time: 1300 CT
• https://go.mil/9soriit6nc
• Call in by phone: +1 503-207-9433,,73745878# 

Monday, Nov. 3 - Bismarck, ND

• Start time: 1300 CT
• Bismarck State College, NECE Bldg.15, Bavendick Stateroom
• 1200 Schafer Street
• Bismarck, ND 58501

Tuesday, Nov. 4 – Fort Pierre, SD

• Start time: 0900 CT
• Casey Tibbs Conference Center
• 210 Verendrye Drive
• Fort Pierre, South Dakota 57532

Tuesday, Nov. 4 – Sioux City, IA    

• Start time: 1630 CT                                                               
• Sioux City Lewis & Clark Interpretive Center                        
• Betty Strong Encounter Center
• 900 Larsen Park Rd
• Sioux City, IA 51103

Reservoir Forecasts:

Gavins Point Dam

• Average releases past month – 23,500 cfs
• Current release rate – 23,500 cfs (as of October 3)
• Forecast release rate – 25,100 cfs (average October release)
• End-of-September reservoir level – 1207.7 feet
• Forecast end-of-October reservoir level – 1207.5 feet
• Notes: Releases will be adjusted as necessary to meet all downstream navigation targets.

Fort Randall Dam

• Average releases past month – 21,200 cfs
• End-of-September reservoir level – 1353.1 feet
• Forecast end-of-October reservoir level – 1345.0 feet
• Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The Fort Randall pool is normally drawn down to 1337.5 feet in the fall to provide space for winter hydropower generation at Oahe and Big Bend. The annual drawdown will continue in October and November

Big Bend Dam

• Average releases past month – 18,900 cfs
• Forecast average release rate – 13,200 cfs
• Forecast end-of-October reservoir level – 1420.4 feet

Oahe Dam

• Average releases past month – 17,500 cfs
• Forecast average release rate – 13,200 cfs
• End-of-September reservoir level – 1600.3 feet (up 0.8 feet since August 31)
• Forecast end-of-October reservoir level – 1600.3 feet

Garrison Dam

• Average releases past month – 16,400 cfs
• Current release rate – 14,000 cfs
• Forecast average release rate – 14,000 cfs
• End-of-September reservoir level – 1831.8 feet (down 0.9 feet since August 31)
• Forecast end-of-October reservoir level – 1830.3 feet

Fort Peck Dam

• Average releases past month – 9,100 cfs
• Current release rate – 4,000 cfs
• Forecast average release rate –4,000 cfs
• End-of-September reservoir level – 2222.5 feet (down 1.9 feet since August 31)
• Forecast end-of-October reservoir level – 2222.1 feet

The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.

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 three-week release forecast for the mainstem dams, go to https://go.mil/mr-3wk-fcast.