U.S. Army Corps of Engineers
News Release
Jan. 20, 2012
Omaha, Neb. – With a stable ice cover established on the Missouri River at Bismarck, the releases from Garrison dam will be gradually increased over the next several weeks.
"Each winter during the freeze-in period, the stage at Bismarck typically rises 5 to 7 feet over a short period of time due to ice formation on the river," said Jody Farhat, Chief of the Corps of Engineers’ Missouri River Water Management office in Omaha. "Once a stable ice cover is established, stages begin to decline and releases from Garrison dam can gradu ally be increased without causing the river to rise. This is due to the smoothing of the underside of the ice and the channel bottom, which creates a more efficient channel."
Stages at other locations between the dam and Bismarck may increase as the ice moves upstream with the continued cold weather, but should remain within the normal range.
Last weekend, the stage at Bismarck rose from 4.5 feet at noon on Friday to 11.2 feet by Saturday evening during the freeze-in. Although stages at the primary river gages at Bismarck and Schmidt were within the normal range for the freeze-in period, stages at some intervening areas were higher than seen in previous years prompting the National Weather Service to issue a flood warning. With a stable ice cover in place, plans are now underway to start gradually began increasing the release from Garrison.
"The ice cover appears stable and stages are slowly drifting down as we anticipated. ; Today's stage is 10 feet, down from a peak of about 11.5 during the freeze-in," said Farhat. "Beginning Saturday Jan 21, releases will be stepped up at a rate of approximately 1,000 cfs every other day until a rate of 26,000 cubic feet per second or 27,000 cfs is reached in early February. This rate will allow us to monitor the impacts of the incremental increases in the Bismarck area before the next change is made and to adjust the schedule if needed."
Releases from Garrison Dam need to be increased to complete the evacuation of flood water out of the flood control pool. The reservoir is currently about 1.3 feet above the base of the annual flood control pool; 1.8 feet lower than last year at this time. Total system storage in the Mainstem Reservoir System, however, is already 0.4 MAF below the base of the annual flood control zone, providing more than the recommended 16.3 MAF of flood control storage or an additional 400,00 acre feet of storage for the 2012 runoff season.
Fort Randall reservoir is lowered each fall and refilled during the winter with water from the upper projects used for winter hydropower generation. Water will continue to be moved from Fort Peck and Garrison downstream into Fort Randall during January and February; Oahe is already below the base of its annual flood control zone.
Current gage data for the Bismarck gage is available on the Corps’ website at:
http://www.nwd-mr.usace.army.mil/rcc/plots/jpegs/bis.jpg
A webcam with a view from the gaging station is available at: https://webcam.crrel.usace.army.mil/bismarck/