Reservoir inflows in the Missouri River basin above Sioux City, Iowa (upper Basin) were well-below average in February. The 2021 calendar year runoff forecast for the upper basin remains below average. 

“Very cold February temperatures in the upper Basin locked up tributaries in ice and reduced inflows to the System reservoirs,” said John Remus, chief of the U.S. Army Corps of Engineers’, Missouri River Basin Water Management Division. “Mountain snowpack continues to accumulate in the Rocky Mountains; however, plains snowpack is well-below seasonal averages and soil moisture continues to be much drier than normal.”

February 2021 runoff in the upper Basin was 0.8 million acre-feet, 70% of average. The 2021 calendar year runoff forecast for the upper Basin is 21.8 MAF, 84% of average. The runoff forecast is based on soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.

“Prior to the outbreak of cold, Arctic air, Gavins Point releases were increased to 19,000 cubic feet per second to lessen the impacts of ice formation on the lower Missouri River. The System hydropower plants increased energy production during the coldest days to compensate for the increased energy demands throughout the region,” added Remus.

System storage is currently 55.6 MAF, 0.5 MAF below the base of the annual flood control zone.  The System is positioned to serve all Congressionally authorized purposes during 2021, including flood control, navigation, and water supply. 

Navigation:

Beginning in mid-March, releases from Gavins Point Dam will be adjusted to provide flow support for Missouri River navigation.  Current studies indicate that flow support for Missouri River navigation will be at the full-service level for the first half of the 2021 season, which begins on April 1 at the mouth. Full-service flow support is generally sufficient to provide a 9-foot-deep by 300-foot-wide channel. The actual service level will be based on the total volume of water stored in 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 actual July 1 System storage. Full-service navigation flow support is expected at the dates and locations shown below.

Ice Conditions:

River ice conditions below all System projects, which have been closely monitored this winter season, will continue to be monitored through the spring ice break-up. In early February, Gavins Point releases were increased to 19,000 cfs prior to the cold weather to lessen the impacts of ice formation on the lower Missouri River. Releases were reduced to 17,000 cfs near the end of February. 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. The river ice report is available at: http://go.usa.gov/xARQc.

Mountain and Plains Snowpack:

Mountain snowpack in the upper Basin is accumulating at below-average rates. The March 1 mountain snowpack in the Fort Peck and the Fort Peck to Garrison reaches was 94% of average. By March 1, about 80% of the total mountain snowpack has typically accumulated. Mountain snowpack normally peaks near April 15. The mountain snowpack graphics can be viewed at: http://go.usa.gov/xARQC. Currently, plains snowpack in the upper Basin is light.

Monthly Water Management Conference for 2021:

The March 2021 monthly conference call will be held on Thursday, March 4, 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 the Defense Video and Imagery Distribution System at https://go.usa.gov/xARQv

Spring Public Meeting:

The spring public meetings will be held virtually on Tuesday, April 6. Meetings will be held at 1 p.m. and 6 p.m. CDT by conference call and webinar. The purpose of this meeting is to update the region on current hydrologic conditions and the planned operation of the mainstem reservoir system during the coming months.

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 18,300 cfs
  • Current release rate – 17,000 cfs
  • Forecast release rate – 17,000 cfs
  • End-of-February reservoir level – 1207.8 feet
  • Forecast end-of-March reservoir level – 1206.0 feet
  • Notes: The Gavins Point release will be increased beginning around March 19 to begin providing full-service navigation flow support on the lower Missouri River.
     
• Fort Randall Dam
  • Average releases past month – 15,100 cfs
  • End-of-February reservoir level – 1350.5 feet (up 4.9 feet from January)
  • Forecast end-of-March reservoir level – 1354.8 feet
  • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point and to back up Gavins Point releases. The reservoir will refill to elevation 1355.0 ft msl by the end of March.
     
• Big Bend Dam
  • Average releases past month – 20,500 cfs
  • Forecast average release rate – 20,800 cfs
  • Forecast reservoir level – 1421.0 feet
     
• Oahe Dam
  • Average releases past month – 20,600 cfs
  • Forecast average release rate – 20,500 cfs
  • End-of-February reservoir level – 1606.6 feet (up 0.1 foot from January)
  • Forecast end-of-March reservoir level – 1607.1 feet
     
• Garrison Dam
  • Average releases past month – 21,300 cfs
  • Current release rate – 20,000 cfs
  • Forecast release rate – 18,000 cfs
  • End-of-February reservoir level – 1836.9 feet
  • Forecast end-of-March reservoir level – 1837.1 feet
  • Notes – Releases will be lowered to 18,000 cfs in early March.
     
• Fort Peck Dam
  • Average releases past month – 10,200 cfs
  • Current release rate – 8,000 cfs
  • Forecast average release rate – 7,000 cfs
  • End-of-February reservoir level – 2233.2 feet
  • Forecast end-of-March reservoir level – 2233.2 feet
  • Notes: Releases will be lowered to 7,000 cfs in early March.

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 637 million kWh of electricity in February. Typical energy generation for February is 624 million kWh. Additional energy was produced to meet energy demands during the cold-Arctic air outbreak in mid-February through intra-system releases. The power plants are expected to generate 9.6 billion kWh this year, compared to the long-term average of 9.5 billion kWh.

To view the detailed three-week release forecast for the mainstem dams, go to https://go.usa.gov/xARQB.

The Missouri Basin Web App provides links to these reports and others that are updated more frequently. http://go.usa.gov/xE6fC.