Posted on October 10, 2023
The month of September brought mixed results for precipitation across the Missouri River Basin. Portions of Montana, North and South Dakota, and Nebraska received above average rainfall, while the remainder of the upper basin and lower basin were below average. Overall, September runoff in the Missouri River Basin above Sioux City, Iowa was 1.3 million acre-feet, 109% of the long-term average. The annual runoff forecast for the upper Missouri River Basin above Sioux City, IA is 29.1 MAF, 113% of average and the same as last month’s forecast.
“Rainfall was above average in portions of the upper Missouri River Basin for the month of September,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.
“Runoff was above average or near average in every reach except Sioux City, which was below average,” Remus added.
Soil Moisture conditions have improved in parts of the basin, but much of the lower basin as well as parts of Montana and North and South Dakota remain abnormally dry. These drought conditions are expected to persist through the end of the year.
Total System storage as of Sept. 30 was 54.2 million acre-feet, which is 1.9 million acre-feet below the base of the flood control zone. System storage is expected to continue to decline through the fall. The updated reservoir studies indicate that the System storage is expected to be approximately 4.0 MAF below the base of flood control at the start of the 2024 runoff season.
Navigation
Gavins Point Dam releases will be set to provide navigation flow support at a level 1,500 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. Navigation support will be provided for the entire navigation season and will end on Dec. 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 13,000 cfs.
Draft Annual Operating Plan
In mid-September, the USACE posted the draft 2023-2024 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. 30.
Fall Public Meetings
Fall public meetings will be held Nov. 7-9. 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/.
Tuesday, Nov. 7 – Poplar, Montana
- Start Time: 10:00 MT
- Fort Peck Community College
- 605 Indian Ave, Poplar, MT 59255
Tuesday, Nov. 7 – Bismarck, North Dakota
- Start time: 17:00 CT
- Bismarck State College, NECE Bldg.15, Bavendick Stateroom
- 1200 Schafer Street, Bismarck, ND
Wednesday, Nov. 8 – Pierre, South Dakota
- Start time: 10:00 CT
- Ramkota Hotel (Lake Rm)
- 920 W Sioux Ave, Pierre, SD 57501
Wednesday, Nov. 8 – Lower Brule, South Dakota
- Start time: 13:00 CT
- Lower Brule Community Center (gymnasium)
- Lower Brule, SD 57548
Thursday, Nov. 9 – Smithville, Missouri
- Start time: 10:00 CT
- Jerry Litton Visitor Center
- 16311 DD Hwy, Smithville, MO 64089
Thursday, Nov. 9 – Bellevue, Nebraska
- Start time: 17:00 CT
- Bellevue University, Hitchcock Humanities Building, 1040 Bruin Blvd, Criss Auditorium
- 1000 Galvin Road South, Bellevue, NE 68005
Reservoir Forecasts:
- Gavins Point Dam
- Average releases past month – 34,900 cfs
- Current release rate – 35,000 cfs (as of Oct. 4)
- Forecast release rate – 35,000 cfs (month of October)
- End-of-September reservoir level – 1206.9 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 – 33,100 cfs
- End-of-September reservoir level – 1354.1 feet
- Forecast end-of-October reservoir level – 1344.6 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 – 32,100 cfs
- Forecast average release rate – 22,000 cfs
- Forecast reservoir level – 1420.7 feet
- Oahe Dam
- Average releases past month – 32,900 cfs
- Forecast average release rate – 22,300 cfs
- End-of-September reservoir level – 1600.3 feet
- Forecast end-of-October reservoir level – 1599.0 feet
- Garrison Dam
- Average releases past month – 19,900 cfs
- Current release rate – 17,000 cfs
- Forecast average release rate – 17,000 cfs
- End-of-September reservoir level – 1840.3 feet
- Forecast end-of-October reservoir level – 1839.2 feet
- Fort Peck Dam
- Average releases past month – 7,400 cfs
- Current release rate – 4,000 cfs
- Forecast average release rate – 4,000 cfs
- End-of-September reservoir level – 2228.8 feet
- Forecast end-of-October reservoir level – 2229.0 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 919 million kWh of electricity in September. Typical energy generation for September is 900 million kWh. The power plants are projected to generate 7.9 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.
