OMAHA, NE - The U.S. Army Corps of Engineers (Corps) Missouri River Basin Water Management Division plans to maintain higher-than-average releases from all System projects, including Gavins Point, over the next several months. “Due to the water currently being stored in the reservoirs and the higher-than-average runoff being forecast in the Missouri River Basin above Sioux City, Iowa, the service level will remain 15,000 cubic feet per second (cfs) above full service to facilitate the evacuation of stored flood waters. The increased service level means that Gavins Point releases will be increased from 42,000 cubic feet per second (cfs) to 44,000 cfs, and possibly higher, as downstream tributary flows recede,” said John Remus, Chief of the Missouri River Basin Water Management Division. Gavins Point releases will be adjusted, when needed, in response to basin conditions. When necessary, the Corps will reduce releases from the System projects and utilize the available flood control space in the reservoirs, in order to lessen flooding downstream of all the projects. It is important to note that the ability to significantly reduce flood risk along the lower Missouri River diminishes at locations further downstream due to the large uncontrolled drainage area and the travel time from Gavins Point Dam.
The 2018 runoff forecast in the Missouri River Basin above Sioux City, Iowa, is 34.6 million acre feet (MAF), 136 percent of average according to the Corps. May runoff in the Fort Peck and Garrison reaches was the second highest on record. “The updated runoff forecast reflects the rapid melting of mountain snowpack in the upper basin as well as widespread rainfall throughout the basin,” said Remus.
As of June 1, the mountain snowpack was 91 percent of average in the reach above Fort Peck and 88 percent of average in the reach from Fort Peck to Garrison. The mountain snowpack peaked on April 19 in the Fort Peck reach and on April 15 in the Fort Peck to Garrison reach. Compared to 2011, the mountain snowpack in 2018 had a lower peak snow water equivalent in both reaches and melted earlier. Both reaches have approximately 6.0 inches of snow water equivalent remaining while at this same time in 2011, there was 19 inches remaining above Fort Peck and 22 inches remaining in the Fort Peck to Garrison reach. View the mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.
The Missouri River mainstem reservoir system (System) storage was 63.4 MAF as of June 1, occupying 7.3 MAF of the 16.3 MAF flood control zone. “More than 50 percent of the System’s flood storage remains available to capture runoff from the remaining mountain snowmelt and summer rainfall events. On June 1, 2011, 12 percent of the total flood control storage was available. The considerable amount of vacant flood control storage provides flexibility to lessen downstream flooding should suddenly-developing large rainfall events occur anywhere in the basin,” said Remus.
Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/weeklyupdate.pdf.
The Corps will continue to monitor basin and river conditions, including rainfall and mountain snowmelt, and will adjust the regulation of the System based on the most up-to-date information.
More information is available here: http://www.nwd.usace.army.mil/Media/News-Releases/Article/1541194/higher-than-average-releases-from-missouri-river-mainstem-projects-to-continue/