The U.S. Army Corps of Engineers began reducing Gavins Point releases to the winter release rate on Nov. 30. The releases will be stepped down at a rate of 3,000 cubic feet per second per day until they reach 27,000 cfs where they are expected to remain through December.

Releases will be reduced to 25,000 cfs in January and remain near that rate for the remainder of the winter. Gavins Point Dam winter releases normally range between 12,000 and 17,000 cfs. Higher-than-average winter releases from the Missouri River Mainstem System projects, including Gavins Point, continue emptying water from the 2019 runoff season still in storage.

“We are monitoring basin and channel conditions very closely and will make any necessary adjustments. Water remaining in flood control storage zones will lead to increased flood risk in 2020. The higher-than-average releases will benefit municipal and industrial water intakes below Gavins Point Dam, which can be impacted by low water levels during periods of ice formation,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division.

The November runoff above Sioux City, Iowa, was 2.0 million acre feet (MAF), 195% of average. The 2019 runoff forecast in the Missouri River Basin above Sioux City is 60.4 MAF, 238% of average. If this forecast is realized, the 60.4 MAF of runoff will be second highest runoff in 121 years of record-keeping (1898-2018), exceeded only by the 61.0 MAF of runoff observed in 2011.

The Missouri River Mainstem Reservoir System total storage was 57.5 MAF as of Dec. 1, occupying 1.4 MAF of the 16.3-MAF flood control zone.

Lower release rates must be set during winter months because the Missouri River ices over in the northern reaches limiting the amount of water that can flow beneath the ice. River ice conditions below all System projects will be closely monitored throughout the winter season. The Corps will also continue to monitor basin and river conditions, including plains and mountain snow accumulation, and will adjust System regulation based on the most up-to-date information.

The mountain snowpack accumulation period is underway. The mountain snowpack normally peaks near April 15. The mountain snowpack graphics can be viewed here:  http://go.usa.gov/xE6wT.

The comment period for the 2019-2020 Annual Operating Plan ended November 22. The final AOP, which is to be completed in late December, will be posted on the Water Management website: https://www.nwd.usace.army.mil/MRWM/Public-Meetings/

Updates on basin conditions, reservoir levels and other topics of interest can be viewed here: https://www.nwd.usace.army.mil/MRWM/MRWMApp/.

Monthly Water Management Conference Calls

Water management calls include an update from the National Weather Service’s Missouri Basin River Forecast Center, an update on the Missouri River mainstem reservoir system operations, and updates on the ongoing and planned flood recovery efforts in both the Omaha and Kansas City districts. The last call for 2019 will be held Thursday, Dec. 5 for Congressional delegations; Tribes; state, county and local government officials, levee and drainage districts; and the media. Calls will be recorded in their entirety and made available to the public on the Defense Video and Imagery Distribution System at www.dvidshub.net/unit/usace-nwd.

Reservoir Forecasts

• Gavins Point Dam
  • Average releases past month – 78,600 cfs
  • Current release rate – 57,000 cfs (as of December 5)
  • Forecast release rate – 27,000 cfs (middle of December)
  • End-of-November reservoir level – 1206.7 feet
  • Forecast end-of-December reservoir level – 1207.5 feet
  • Notes: Releases will be reduced 3,000 cfs per day until releases reach 27,000 cfs where they will remain through December. Releases will then be reduced to 25,000 cfs in January where they will remain for the rest of winter.
     
• Fort Randall Dam
  • Average releases past month – 74,200 cfs
  • End-of-November reservoir level – 1337.9 feet (down 10.3 feet from October)
  • Forecast end-of-December reservoir level – 1339.1 feet
  • Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The reservoir is normally drawn down to 1337.5 feet in the fall to provide space for winter hydropower generation at Oahe and Big Bend. The reservoir will be refilled December – February.
     
• Big Bend Dam
  • Average releases past month – 62,400 cfs
  • Forecast average release rate – 33,400 cfs
  • Forecast reservoir level – 1420.5 feet
     
• Oahe Dam
  • Average releases past month – 64,900 cfs
  • Forecast average release rate – 33,800 cfs
  • End-of-November reservoir level – 1610.1 feet (falling 3.0 feet during November)
  • Forecast end-of-December reservoir level – 1607.3 feet


• Garrison Dam
  • Average releases past month – 42,500 cfs
  • Current release rate – 22,000 cfs
  • Forecast average release rate – 22,000 cfs
  • End-of-November reservoir level – 1839.1 feet (falling 3.3 feet during November)
  • Forecast end-of-December reservoir level – 1838.9 feet
• Notes – Releases will be reduced to 16,000 cfs prior to the river freeze-in at Bismarck, North Dakota. Current forecasts show this occurring in late December. Once an ice cover is established, releases will be gradually increased to 24,500 cfs.
   
• Fort Peck Dam
  • Average releases past month – 15,300 cfs
  • Current release rate – 15,000 cfs
  • Forecast average release rate – 13,000 cfs
  • End-of-November reservoir level – 2238.8 feet (down 1.9 feet from October)
  • Forecast end-of-December reservoir level – 2237.3 feet
  • Notes: Releases will remain at 15,000 cfs until lake and river ice begins forming. When this occurs, the spillway will close and releases will be reduced to 13,000 cfs.

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 1276 million kWh of electricity in November. Typical energy generation for November is 741 million kWh. The power plants are projected to generate 13.1 billion kWh of electricity this year, compared to the long-term average of 9.4 billion kWh.

“The higher-than-average winter releases will provide additional hydropower generation during the winter, which is one of the peak power demand periods,” said Remus.

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