Posted on February 8, 2023
The updated 2023 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average.
January runoff in the Missouri River Basin above Sioux City was 1.1 million acre-feet, 134% of average. Runoff was above average due to warmer-than-normal temperatures in the upper basin resulting in some snowmelt runoff. Precipitation in January was below normal for most of the upper basin except for southern South Dakota, which saw above-normal precipitation.
“Despite January’s runoff being above average, we expect 2023 runoff to remain below average,” said John Remus, chief of the U.S. Army Corps of Engineers’, Missouri River Basin Water Management Division. “Drought conditions currently exist across most of the basin.”
The 2023 calendar year runoff forecast above Sioux City is 21.1 MAF, 82% of average. The runoff forecast is based on current soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.
At the start of the 2023 runoff season, which typically begins around March 1, the total volume of water stored in the Missouri River Mainstem Reservoir System is expected to be 46.0 MAF, 10.1 MAF below the top of the carryover multiple use zone.
To conserve water in the System, minimum releases from Gavins Point Dam are scheduled this winter while still serving the needs of the municipal, industrial and powerplant water intakes along the lower river.
“While the winter target release from Gavins Point Dam is 12,000 cfs, releases were increased to 14,000 cfs in late January and early February to mitigate some of the effects of the much colder temperatures across the lower basin,” said Remus. Releases are currently at 13,000 cfs and will be reduced to 12,000 cfs on Feb. 7. “With weather conditions and river stages forecast to be more seasonal over the next few weeks, System releases are returning to the minimum winter rates,” said Remus.
Basin and river conditions continue to be monitored, including plains and mountain snow accumulation, and System regulation will be adjusted based on the most up-to-date information.
Navigation flow support for the Missouri River is forecast to be at minimum service for the first half of the 2023 season, which begins April 1 at the mouth of the river near St. Louis, Missouri. The actual service level will be based on the total volume of water stored within the System on March 15, in accordance with the guidelines in the Master Manual. Flow support for the second half of the navigation season, as well as navigation season length, will be based on the storage in the System on July 1.
Mountain and Plains Snowpack:
Mountain snowpack in the upper Missouri River Basin is accumulating at near average rates. The Feb. 1, mountain snowpack in the Fort Peck reach was 107% of average, while the mountain snowpack in the Fort Peck to Garrison reach was 99% of average. By Feb. 1, about 60% of the total mountain snowfall has typically accumulated. Mountain snow normally peaks near April 17. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.
The plains snowpack, which typically melts from mid-February into April, is currently above normal. Two to four inches of snow water equivalent (SWE) covers eastern Montana and much of the Dakotas. Some areas in the central and eastern Dakotas are showing up to five inches of SWE.
Monthly Water Management Conference Calls for 2023:
The February 2023 monthly conference call will be held Thursday, Feb. 9, to inform basin stakeholders of current weather and runoff forecasts and the planned operation of the reservoir system in the coming months. Presentation materials will be available via webinar. The call is intended for Congressional delegations; Tribes; state, county and local government officials; and the media. It will be recorded in its entirety and made available to the public on our website at https://go.usa.gov/xARQv.
Save the Date: Spring Public Meetings:
The Northwestern Division, Missouri River Basin Water Management Division will host a series of public meeting on the Week of April 3, 2023. The meeting will be held at the following locations, meeting times are being finalized.
- April 3 – Poplar MT and in Bismarck, ND
- April 4 – Pierre, SD and Lower Brule, SD
- April 5 – Smithville, MO and Omaha/Bellevue, NE
- April 6 – St. Louis, MO
- Gavins Point Dam
- Average releases past month – 13,100 cfs
- Current release rate – 13,000 cfs
- Forecast release rate – 12,000 cfs
- End-of-January reservoir level – 1207.5 feet
- Forecast end-of-February reservoir level – 1206.0 feet
- Notes: The winter release rate will be at least 12,000 cfs and may be adjusted to lessen the impacts of winter ice formation.
- Fort Randall Dam
- Average releases past month – 10,700 cfs
- End-of-January reservoir level – 1345.6
- Forecast end-of-February reservoir level – 1349.6 feet
- Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The reservoir was drawn down to 1337.5 feet near the end of November 2022 to provide space for winter hydropower generation at Oahe and Big Bend. The reservoir will refill to the base of the flood control pool by the end of February.
- Big Bend Dam
- Average releases past month – 15,900 cfs
- Forecast average release rate – 13,900 cfs
- Forecast reservoir level – 1420.8 feet
- Oahe Dam
- Average releases past month – 15,800 cfs
- Forecast average release rate – 14,100 cfs
- End-of-January reservoir level – 1591.5 feet
- Forecast end-of-February reservoir level – 1593.8 feet
- Garrison Dam
- Average releases past month – 23,200 cfs
- Current release rate – 23,500 cfs
- Forecast average release rate – 23,500 cfs
- End-of-January reservoir level – 1827.9 feet
- Forecast end-of-February reservoir level – 1825.7 feet
- Notes – Releases were set at 16,000 cfs prior to the river freeze-in at Bismarck, North Dakota. Releases were gradually increased to 23,500 cfs as downstream conditions permitted to benefit winter hydropower generation and to better balance storage in the upper three reservoirs.
- Fort Peck Dam
- Average releases past month – 6,400 cfs
- Current release rate – 6,500 cfs
- Forecast average release rate – 6,500 cfs
- End-of-January reservoir level – 2218.9 feet
- Forecast end-of-February reservoir level – 2219.0 feet
- Notes: Releases will remain at 6,500 cfs in February.
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.
The six mainstem power plants generated 556 million kWh of electricity in January. Typical energy generation for January is 709 million kWh. Forecast generation for 2023 is 7.6 billion kWh 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