The updated 2025 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. April runoff in the Missouri River Basin above Sioux City was 1.4 million acre-feet, 48% of average.

“Runoff into the reservoir system was below average for the month of April, and runoff was below average in all reaches,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “Drought or abnormally dry conditions are currently present in 75% of the basin, and conditions have worsened in the Fort Peck reach and parts of the Garrison reach in the last month.  As a result, the runoff forecast was lowered by 1.9 MAF from last month.” 

The 2025 calendar year runoff forecast above Sioux City is 20.0 MAF, 78% of average. The runoff forecast is based on current soil moisture conditions, mountain snowpack, and long-term precipitation and temperature outlooks.

The volume of water stored in the Missouri River Mainstem Reservoir System is currently 50.4 MAF, 5.7 MAF below the top of the carryover multiple use zone.

Fort Peck releases will be increased to 10,500 cfs in mid-May.  Garrison releases will be increased to 24,000 cfs around mid-May.  Releases are expected to stay at those rates through the summer.

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:

Gavins Point Dam releases will continue to provide navigation flow support at 4,000 cfs below full service for the first half of the navigation season.  The flow support began April 1 at the mouth of the river near St. Louis, Missouri. The service level was 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 Snowpack:

The mountain snowpack was below normal and peaked earlier than normal. The Fort Peck reach peaked at 92% of average on April 5 and 69% of the 2025 peak remained on May 4. The Garrison reach peaked at 95% of average on April 5 and 84% of the 2025 peak remains. Mountain snow normally peaks near April 17. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC.  

Monthly Water Management Conference Calls for 2025:

The May 2025 monthly conference call will be held Thursday, May 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.

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 25,700 cfs
  • Current release rate – 25,000 cfs
  • Forecast release rate – 28,000 cfs
  • End-of-April reservoir level – 1206.7 feet
  • Forecast end-of-May reservoir level – 1206.0 feet
  • Notes: The Gavins Point release will be adjusted as needed to provide navigation flow support on the lower Missouri River.
     
• Fort Randall Dam
  • Average releases past month – 23,400 cfs
  • End-of-April reservoir level – 1355.7
  • Forecast end-of-May reservoir level – 1355.2 feet
  • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up the Gavins Point release increases.
     
• Big Bend Dam
  • Average releases past month – 25,500 cfs
  • Forecast average release rate – 24,500 cfs
  • Forecast reservoir level – 1420.7 feet
     
• Oahe Dam
  • Average releases past month – 24,800 cfs
  • Forecast average release rate – 24,500 cfs
  • End-of-April reservoir level – 1597.4 feet
  • Forecast end-of-May reservoir level – 1597.3 feet
     
• Garrison Dam
  • Average releases past month – 17,900 cfs
  • Current release rate – 21,000 cfs
  • Forecast average release rate – 24,000 cfs
  • End-of-April reservoir level – 1830.8 feet
  • Forecast end-of-May reservoir level – 1831.4 feet
     
• Fort Peck Dam
  • Average releases past month – 6,700 cfs
  • Current release rate – 9,000 cfs
  • Forecast average release rate – 10,500 cfs
  • End-of-April reservoir level – 2227.6 feet
  • Forecast end-of-May reservoir level – 2227.3 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 727 million kWh of electricity in April. Typical energy generation in April is 695 million kWh. Forecast generation for 2025 is 8.6 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 http://go.usa.gov/xVgWr.