Missouri River Reservoirs Ready For 2019

The Corps of Engineers announced February 7 that all 2018 stored flood waters were evacuated from the Missouri River mainstem reservoir system as of January 29. The full 16.3 million acre-feet (maf.) of designated flood control storage is available to manage 2019 runoff.

“The system stands ready to capture spring runoff, reducing flood risk while providing support to other authorized project purposes,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division. “Current Gavins Point releases are 20,000 cubic feet per second (cfs.) and will be decreased to 17,000 cfs. by mid-February.”

The latest annual runoff forecast for the Missouri River basin above Sioux City, Iowa, is 25.6 maf., slightly more than the long-term average of 25.3 maf.

Runoff into Fort Peck and Garrison is expected to be below average over the next few months due to the lighter-than-average plains snowpack and below-average mountain snowpack. Runoff in the Sioux City reach is expected to be above average over the next few months as the northern portions of the James River and Big Sioux River basins have widespread and moderate-to-heavy plains snowpack.

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The Corps said that portions of those basins contain 4 to 5 inches of estimated liquid content in the snowpack. The remainder of the upper and lower Missouri River basin has light to no snow cover. The Corps is cooperating with other agencies to acquire plains snow measurements in the upper basin.

As of February 4, the mountain snowpack was 88 percent of average in the reach above Fort Peck and 89 percent of average in the reach from Fort Peck to Garrison. Normally, by February 1, 64 percent of the total mountain snowpack accumulation has occurred. Mountain snowpack will continue to accumulate over the next few months and normally peaks in mid-April.

According to the Corps, current studies indicate flow support for Missouri River navigation will be at full service levels for the first half of the 2019 season, which begins on April 1 at the mouth. The actual service level will be based on the total volume of water stored in the system on March 15, in accordance with the guidelines in the Master Manual. Flow support for the second half of the navigation season, as well as navigation season length, will be based on the actual July 1 system storage.