Corps Responds To Melting Snowpack, Increases Missouri River Reservoir Releases

The Corps of Engineers Missouri River Basin Water Management Division announced May 22 it has increased releases from Fort Peck and Garrison dams due to high inflows from rapidly melting mountain snowpack.

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,” said John Remus, chief of the division. “Releases are being increased at Fort Peck and Garrison in response to this runoff. 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 Dam, which is the head of navigation—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 cfs. above full service to facilitate the evacuation of stored flood waters,” Remus said.

Gavins Point releases are currently 40,000 cfs.

The Missouri River mainstem reservoir system storage was 62.2 million acre-feet (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,” Remus said.