The updated 2021 calendar year runoff forecast for the Missouri River Basin above Sioux City, Iowa, continues to be below average. 

“Despite runoff being slightly above average in January, we expect 2021 runoff to be below average,” said John Remus, chief of the U.S. Army Corps of Engineers’, Missouri River Basin Water Management Division. “Both plains snowpack and mountain snowpack continue to lag behind seasonal averages, and soil moisture continues to be much drier-than-normal.”

January 2021 runoff in the Missouri River Basin above Sioux City was 1.1 million acre-feet, 141% of average. The above-average January runoff was primarily due to above-normal temperatures melting any accumulated plains snowpack and inhibiting river ice formation.

The 2021 calendar year runoff forecast above Sioux City is 22.9 MAF, 89% of average. The runoff forecast is based on soil moisture conditions, plains snowpack, mountain snowpack, and long-term precipitation and temperature outlooks.

Gavins Point releases will be maintained at the winter release rate of 17,000 cubic feet per second but will be adjusted if needed in response to ice formation on the Missouri River below Gavins Point Dam.

“System storage remains slightly below the base of the annual flood control zone.  The System is in good position to serve all Congressionally authorized purposes including flood control, navigation, and water supply during 2021,” Remus added. 

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 April 1 at the mouth in St. Louis, Missouri. 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.

Ice Conditions:

River ice conditions below all System projects will be closely monitored throughout the winter season. The Missouri River froze in at Bismarck, N.D. near the end of January.  Garrison releases are gradually being increased from 16,000 cfs to 22,000 cfs.  Garrison releases are typically increased following the formation of a stable ice cover to benefit winter hydropower generation. 

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 Jan. 31 mountain snowpack in the Fort Peck reach was 78% of average, while the mountain snowpack in the Fort Peck to Garrison reach was 79% of average. By February 1, about 60% 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.

Final 2020-2021 Annual Operating Plan Released:

The final Annual Operating Plan for the Missouri River Basin for 2020–2021 has been posted at https://www.nwd.usace.army.mil/MRWM/Public-Meetings/.

Monthly Water Management Conference Calls Begin for 2021:

The February 2021 monthly conference call will be held on Thursday, Feb. 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.

Reservoir Forecasts:

• Gavins Point Dam
  • Average releases past month – 17,000 cfs
  • Current release rate – 17,000 cfs
  • Forecast release rate – 17,000 cfs
  • End-of-January reservoir level – 1207.0 feet
  • Forecast end-of-February reservoir level – 1206.0 feet
  • Notes: The winter release rate will be at least 17,000 cfs and may be adjusted to lessen the impacts of winter ice formation.
     
• Fort Randall Dam
  • Average releases past month – 13,600 cfs
  • End-of-January reservoir level – 1345.6 feet (up 6.2 feet from December)
  • 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 2020 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 – 17,800 cfs
  • Forecast average release rate – 18,300 cfs
  • Forecast reservoir level – 1421.0 feet
     
• Oahe Dam
  • Average releases past month – 18,300 cfs
  • Forecast average release rate – 18,300 cfs
  • End-of-January reservoir level – 1606.5 feet (down 0.5 foot from December)
  • Forecast end-of-February reservoir level – 1607.4 feet
     
• Garrison Dam
  • Average releases past month – 16,400 cfs
  • Current release rate – 20,000 cfs
  • Forecast average release rate – 22,000 cfs
  • End-of-January reservoir level – 1838.2 feet
  • Forecast end-of-February reservoir level – 1837.4 feet
  • Notes – Releases were set at 16,000 cfs prior to the river freeze-in at Bismarck, North Dakota. Release are being gradually increased to 22,000 cfs to benefit winter hydropower generation.
     
• Fort Peck Dam
  • Average releases past month – 10,500 cfs
  • Current release rate – 10,500 cfs
  • Forecast average release rate – 10,000 cfs
  • End-of-January reservoir level – 2234.3 feet
  • Forecast end-of-February reservoir level – 2233.5 feet
  • Notes: Releases will remain at 10,000 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.

Hydropower:

The six mainstem power plants generated 618 million kWh of electricity in January. Typical energy generation for January is 715 million kWh.  The power plants are expected to generate 9.2 billion kWh 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 https://go.usa.gov/xARQB.

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

The numbers in the Energy Generation table were corrected on 2/5/2021