Below Average Runoff Expected For Mainstem System
For the 2024 calendar year, Missouri River basin runoff above Sioux City, Iowa totaled 23.3 million acre-feet, 91 percent of average.
Dry conditions continue to affect the upper Missouri River Basin at the start of the 2025 calendar year, so the U.S. Army Corps of Engineers is forecasting below-average runoff into the mainstem reservoir system. For 2025, runoff in the Missouri River basin above Sioux City,is forecast to be 20.2 MAF, 79 percent of average.
The 2025 forecast is based on current runoff trends, drier than normal soil conditions, and below-average plains and mountain snowpack. At the start of the 2025 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 50.4 MAF, 5.7 MAF below the top of the carryover multiple use zone. The system is designed to use the water contained within the carryover multiple use zone to support the eight Congressionally authorized purposes during extended droughts. Those purposes are flood control, navigation, water supply, irrigation, hydropower, recreation, water quality control, and fish and wildlife.
Releases from Gavins Point Dam were increased from 12,000 cubic feet per second to 14,000 cfs on Dec. 28, prior to the recent cold weather. Releases are scheduled to be reduced to the 12,000 cfs winter release rate later in the week as the ice cover stabilizes.
“Winter releases from Gavins Point Dam will remain low during January and February in order to conserve water in the System, based on the guidance in the Missouri River Mainstem System Master Manual,” said John Remus, chief of the Missouri River Basin Water Management Division. There is enough water in the river for all water supply needs. Access to the water remains the responsibility of the facility owners and operators. “Weather and river conditions continue to be monitored and releases from Gavins Point Dam will be adjusted to the extent practical to help mitigate any negative effects of the cold weather. We know the importance of our operations to water supply,” added Remus.
Navigation: Navigation flow support for the Missouri River is forecast to be 4,000 cfs below full service for the first half of the 2025 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 below- average rates. The Jan, 5, mountain snowpack in the Fort Peck reach was 85% of average, while the mountain snowpack in the Fort Peck to Garrison reach was 75% of average. More than half the mountain snowfall typically occurs from January 1 to mid-April, and normally peaks near April 17. The mountain snowpack graphics can be viewed at: http://go.usa.gov/ xARQC.
Final 2024-2025 Annual Operating Plan Released: The final Annual Operating Plan for the Missouri River Basin for 2024–2025 has been posted at https://www.nwd. usace.army.mil/MRWM/Reports/.
Monthly Water Management Conference Calls Begin for 2025: The first 2025 monthly conference call will be held Wednesday, Jan. 8, 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.
Fort Peck Dam Reservoir Forecast
• Average releases past month – 5,600 cfs
• Current release rate – 5,500 cfs
• Forecast average release rate – 5,500 cfs
• End-of-December reservoir level – 2226.2 feet
• Forecast end-of-January reservoir level – 2225.6 feet
• Notes: Releases will remain at 5,500 cfs in January and 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.
