September runoff in the upper Missouri River Basin was well-below average, continuing the trend of below-average runoff in 2024. “Although Montana precipitation was wetter-than-normal in September, much of the basin was very dry and warm, causing the September runoff in all reaches above Gavins Point to be well-below average,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.

“Runoff in the basin below Sioux City has also been well-below average during late summer and fall, so System releases from Gavins Point Dam have been increased to maintain the flow support level to meet downstream navigation targets,” Remus added.

Except for central Montana, which received greater than 150% of normal precipitation in a few days during late September, widespread areas of the upper Missouri River Basin received less than 25% of normal precipitation. According to the Sept. 24 drought monitor, over 81% of the Missouri River Basin is under abnormally dry or drought conditions. As a result, September runoff was 0.8 million acre-feet, 66% of average above Sioux City. The updated 2024 calendar year forecast for the upper Basin above Sioux City is 23.5 MAF, 91% of average, and 18.3 MAF above Gavins Point Dam, 79% of average. Average annual runoff for the upper Basin above Sioux City is 25.7 MAF.

As of Oct. 1, the total volume of water stored in the System was 53.5 MAF, which is 2.6 MAF below the base of the System’s flood control zone. System storage is forecasted to continue declining through the fall. The updated reservoir studies indicate that the System storage is expected to be 50.9 MAF at the start of the 2025 runoff season, approximately 5.2 MAF below the base of flood control.

Navigation
Gavins Point Dam releases are being set to provide navigation flow support at a level 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. Season support 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 from the Sept. 1 System storage. Per the Sept. 1 System storage, winter releases from Gavins Point Dam will be at least 12,000 cubic feet per second. In anticipation of the low winter releases, a letter was sent to water users below Gavins Point Dam making them aware of the planned releases and encouraging them to assess the risk to their facilities.

Draft Annual Operating Plan
In September, the USACE posted the draft 2024-2025 Annual Operating Plan on its website at: https://www.nwd.usace.army.mil/MRWM/Public-Meetings/. The comment period on the draft AOP will close on Nov. 27. 

Fall Public Meetings
The Northwestern Division will host a series of public meetings the week of Oct. 28. Specific dates, times and locations are listed below and can be found on the website at https://www.nwd.usace.army.mil/MRWM/Public-Meetings/.

Monday, Oct. 28 – Fort Peck, MT

• Start time: 11:00 a.m. Mountain
• Fort Peck Interpretive Center
• Lower Yellow Stone Rd.
• Fort Peck, MT 59223

Monday, Oct. 28 – Bismarck, ND

• Start time: 6:00 p.m. Central
• Bismarck State College, NECE Bldg.15; Rm 304 (auditorium)
• 1200 Schafer Street
• Bismarck ND 58501

Tuesday, Oct. 29 - Pierre, SD

• Start time: 10:00 a.m. Central
• Casey Tibbs Conference Center
• 210 Verendrye Drive
• Ft. Pierre, South Dakota 57532

Tuesday, Oct. 29 – Sioux City, IA

• Start time: 4:00 p.m. Central
• Sioux City Lewis & Clark Interpretive Center
• Betty Strong Encounter Center
• 900 Larsen Park Rd.
• Sioux City, IA 51103

Wednesday, Oct. 30 – St Louis, MO

• Start time: 11:00 a.m. Central
• VUE 17 Event Center                                                                                                
• 1034 S. Brentwood Blvd., #1700
• St. Louis, MO 63117

Thursday, Oct. 31 – Smithville, MO

• Start time: 11:00 a.m. Central
• Jerry Litton Visitor Center
• 16311 DD Hwy
• Smithville, MO 64089

Thursday, Oct. 31 – Nebraska City, NE

• Start time: 4:00 p.m. Central
• Lewis and Clark Interpretive Center
• 100 Valmont Drive
• Nebraska City, NE 68410

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 33,500 cfs
  • Current release rate – 34,000 cfs (as of Oct. 2)
  • Forecast release rate – 34,000 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 – 33,600 cfs
  • End-of-September reservoir level – 1351.3 feet
  • Forecast end-of-October reservoir level – 1344.9 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 – 29,700 cfs
  • Forecast average release rate – 25,900 cfs
  • Forecast reservoir level – 1420.7 feet
     
• Oahe Dam
  • Average releases past month – 30,200 cfs
  • Forecast average release rate – 25,800 cfs
  • End-of-September reservoir level – 1601.4 feet (down 3.0 feet since Aug. 31)
  • Forecast end-of-October reservoir level – 1598.5 feet
     
• Garrison Dam
  • Average releases past month – 18,200 cfs
  • Current release rate – 14,000 cfs
  • Forecast average release rate – 14,000 cfs
  • End-of-September reservoir level – 1838.7 feet (down 1.4 feet since Aug. 31)
  • Forecast end-of-October reservoir level – 1837.6 feet
     
• Fort Peck Dam
  • Average releases past month – 6,900 cfs
  • Current release rate – 4,000 cfs
  • Forecast average release rate –4,000 cfs
  • End-of-September reservoir level – 2227.0 feet (down 0.5 feet since Aug. 31)
  • Forecast end-of-October reservoir level – 2226.9 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 878 million kWh of electricity in September. Typical energy generation for September is 901 million kWh. The power plants are projected to generate 8.1 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 http://go.usa.gov/xVgWr.