– The U.S. Army Corps of Engineers Missouri River Basin Water Management Division has increased releases from Fort Peck and Garrison Dams due to high inflows from rapidly melting mountain snowpack. Garrison Dam releases were stepped up from 37,000 cfs in early May to 39,000 cfs by May 23. Fort Peck Dam releases were gradually increased from 14,000 cfs in mid-May to 17,000 cfs by May 22. The Fort Peck Dam release is higher than the maximum powerhouse release, so releases are being made from both the powerhouse and spillway. Releases from Fort Peck and Garrison are expected to remain at these rates into the summer.
Mountain snowpack peaked on April 19 in the Fort Peck reach and on April 15 in the Fort Peck to Garrison reach at 141 and 137 percent of average, respectively. “About half of the peak mountain snow has melted and is making its way to the reservoirs. Releases are being increased at Fort Peck and Garrison in response to this runoff,” said John Remus, Chief of the Missouri River Basin Water Management Division. “Mostly due to the high mountain snowpack, runoff in the upper basin during the snowmelt months of May through July is expected to be about 130 percent of average.”
As previously announced, the Corps plans to maintain higher-than-average releases from all System projects, including Gavins Point, over the next several months. “Due to higher-than-average runoff being forecast in the Missouri River Basin above Sioux City, Iowa, we have increased the service level 15,000 cubic feet per second (cfs) above full service to facilitate the evacuation of stored flood waters,” said Remus. Gavins Point releases are currently 40,000 cfs.
The Missouri River mainstem reservoir system (System) storage was 62.2 MAF as of May 21, occupying 6.1 MAF of the 16.3 MAF flood control zone. “More than 60 percent of the System’s flood storage is available to capture runoff from the remaining mountain snowmelt and spring and summer rainfall events,” 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.
To view the detailed three-week release forecast for the mainstem dams, go to http://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf.
Release no. 18-034