Heavy rains in August have caused the U.S. Army Corps of Engineers to release more water from the four lower Missouri River dams. Corps officials say thety will carefully monitor downstream conditions and adjust releases this fall to provide flood risk reduction and continue evacuation of stored flood water.
The U.S. Army Corps of Engineers Missouri River Basin Water Management Division is releasing more water at the four lower dams on the Missouri River following heavy rains in August.
The higher releases will evacuate floodwater stored in the Mainstem Reservoir System, preparing it to capture next year’s anticipated runoff and decreasing potential future flood risk. The excess water also will allow the corps to extend the navigation season 10 days and provide higher winter releases, which will benefit winter hydropower generation and reduce risks to water intakes during periods of ice formation this winter. Runoff above Sioux City, Iowa, in August was 3.2 million acre feet (MAF), 241 percent of normal. The 2014 runoff forecast is 35.6 MAF, 141 percent of normal. Average annual runoff is 25.2 MAF.
“Rains in the upper basin have swelled tributary rivers and increased runoff into the reservoir system. August runoff was the third highest since 1898,” said Jody Farhat, chief of the Missouri River Basin Water Management Division. “The Corps’ reservoir system remains within normal operating levels, but the higher runoff has resulted in the need to evacuate water from the system this fall above the rate required for navigation. Releases at the lower four projects, Oahe, Big Bend, Fort Randall and Gavins Point dams, which had been scheduled to meet full-service navigation requirements downstream, will be increased to ensure the entire flood control capacity of the system is available for next year’s runoff.”
The total volume of water stored in the reservoir system is 61.3 MAF. Currently, 5.2 MAF of the 16.3 MAF combined flood control storage is occupied.
“Releases from Gavins Point Dam will be stepped up from the current release rate of 38,000 cubic feet per second (cfs) to 45,500 cfs during the next several days, and are expected to remain near that level throughout the fall. By evacuating the excess water from the reservoir system at the lowest possible rate for the longest period of time, the updated release plan will properly prepare the reservoir system for next year’s runoff season, while reducing downstream flood risk this fall,” Farhat said. “Although releases are higher than normal for this time of year, flows are expected to remain in the channel unless we experience a significant amount of rain.”
The corps will carefully monitor downstream conditions and adjust Gavins Point Dam releases as necessary this fall to provide flood risk reduction and continue evacuation of stored flood water. Based on the Sept. 1 reservoir system storage, there will be a 10-day extension to the navigation season with Gavins Point winter releases of 20,000 cfs. Navigation service at the mouth of the Missouri River will now end on Dec. 10. Both the longer navigation season and the higher winter release will better serve downstream water users during the remainder of the year. Winter releases are normally near 17,000 cfs.
The Corps will continue to monitor basin conditions and fine tune the regulation of the reservoir system based on up-to-date information. Read more at: http://www.nwd.usace.army.mil/Media/NewsReleases/tabid/1989/Article/496565/corps-increases-releases-to-lessen-future-flood-risk.aspx.