The U.S Army Corps of Engineers (Corps) Missouri River Water Management Office increased releases from Gavins Point Dam from 17,000 cubic feet per second (cfs) to 20,000 cfs in late December and early January to offset water lost to ice formation in anticipation of cold temperatures forecasted to enter the basin. 

“Extremely cold weather locked Missouri River flows into ice and caused dips in river stages below Gavins Point,” said Jody Farhat, chief of the Water Management Division.  “Releases will be adjusted, as necessary, to maintain downstream river stages.”  Releases will likely be reduced when more moderate temperatures return to the area. 

Based on the current soil moisture and mountain and plains snowpack conditions, 2015 runoff in the Missouri River Basin above Sioux City, Iowa, is forecast to be 25.6 million acre feet (MAF).  Normal runoff is 25.2 MAF.  Annual runoff in 2014 was 35.0 MAF, which ranks eleventh highest in the 118 years on record. 

The high runoff was the product of above normal mountain snowmelt runoff coupled with persistent summer rainfall in Montana and the Dakotas. “Rainfall events continued to occur in the upper basin through late August at a time of year when rainfall amounts historically diminish,” said Farhat.  “Fall releases were increased to ensure the full flood control storage zone is available for the 2015 runoff season, which typically begins around March 1.”  

System storage ended December at 56.4 MAF, just 0.3 MAF above the base of the annual flood control zone.  Bitter cold temperatures in early January reduced inflows into the reservoir system as tributary rivers froze and system storage dropped sharply.  “Current system storage is 56.0 MAF, 0.1 MAF below the base of the annual flood control system,” said Farhat.  “The entire flood control capacity of the mainstem reservoir system stands ready to capture high runoff in the spring, reducing flood risk while providing good support to other authorized project purposes.” 

Flow support for Missouri River navigation will likely be at full service levels for the first half of the 2015 season.  The actual service level will be based on the total volume of water stored in the reservoir system on March 15 in accordance with guidelines in the Master Manual. Flow support for the second half of the navigation season, as well as the navigation season length, will be based on the actual July 1 system storage. 

As of Jan. 1, the mountain snowpack was 101 percent of normal in the reach above Fort Peck Dam and 101 percent of normal in the reach from Fort Peck to Garrison Dam. Light plains snowpack has accumulated in western South Dakota and Montana with less snow seen in North Dakota. 

“The Corps will continue to monitor the plains and mountain snowpack, and basin soil conditions through the winter and into spring to fine tune the regulation of the reservoir system based on the most up-to-date information,” said Farhat. 

View mountain snowpack graphic here: https://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.   

Final 2014–2015 Annual Operating Plan released

After reviewing comments received on the draft, the Missouri River Basin Water Management Division developed and released the Final Annual Operating Plan for the Missouri River Basin for 2014–2015. The plan is posted at https://www.nwd-mr.usace.army.mil/rcc/aop.html. 

Monthly water management conference calls begin for 2015 

The Corps will host its first conference call of 2015 on Tuesday, Jan. 13, to inform basin stakeholders on 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 as a free podcast in iTunes. Subscribe at https://itunes.apple.com/podcast/missouri-river-basin-water/id508457675, or, search for Missouri River Basin Water Management in iTunes. The audio file will also be posted to the Omaha District’s facebook page and other social media outlets following each call.

Reservoir forecasts

Gavins Point Dam releases averaged 19,700 cfs during December. Releases are expected to average 19,000 cfs in January.  The reservoir behind Gavins Point Dam ended December at elevation 1206.5 feet. The pool elevation will increase to 1207.5 feet this month. 

Fort Randall Dam releases averaged 16,900 cfs during December. Releases are expected to average 18,100 this month and will be adjusted, as necessary, to maintain the elevation at Gavins Point. The reservoir ended December at elevation 1341.1 feet. It is forecast to rise 3.7 feet by the end of the month. The refill of the reservoir is designed to increase winter hydropower generation at Oahe and Big Bend dams. 

Big Bend Dam releases averaged 17,300 cfs during December. They are expected to average 21,600 cfs this month. The reservoir will remain near its normal elevation of 1420 feet.  

Oahe Dam releases averaged 18,600 cfs during December. Releases are expected to average 21,100 cfs this month. The reservoir ended December at elevation 1607.4 feet, down 0.5 feet during the month. The reservoir is expected to fall 0.2 feet during the month of January. 

Garrison Dam releases averaged 16,100 cfs in December. Releases were reduced to 16,000 cfs in late November to prepare for the river freeze-in and were increased to 17,000 cfs in early January.  As ice conditions permit, releases will be gradually increased to the winter release rate of 23,000 cfs.  The reservoir ended December at 1840.4 feet, down 0.5 feet from the previous month.  The reservoir is expected to decline 1.4 feet in January. 

Fort Peck Dam releases averaged 5,700 cfs in December. Releases were increased to 6,500 cfs in early January. The reservoir ended the month at elevation 2233.5 feet, up 0.3 foot from the previous month and is forecast to remain steady this month. 

The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other unknown circumstances could cause adjustments to the reservoir release rates.  

The six mainstem power plants generated 606 million kilowatt hours (kWh) of electricity in December. Average power generation in December is 687 million kWh. The 2014 total power generation was 9.6 billion kWh. The power plants are projected to generate 9.6 billion kWh of electricity this year, compared to the normal of 10 billion kWh. 

To view the detailed three-week release forecast for the mainstem dams, go to: https://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf. 

MISSOURI RIVER MAINSTEM RESERVOIR DATA

WATER RELEASES AND ENERGY GENERATION FOR DECEMBER