Missouri Basin Runoff Expected To Finish Year At 74 Percent Of Average

As planned, the Corps of Engineers reduced releases from Gavins Point Dam on November 21, ending flow support for navigation on the Missouri River.

“Releases from Gavins Point Dam are being reduced to the winter release of 12,000 cubic feet per second (cfs.),” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division, in a December 8 news release. “Releases from Gavins Point are currently 13,000 cfs. and we will reduce releases to 12,000 by December 11. We will closely monitor river conditions, and releases will be adjusted this winter to the extent practical to lessen the impacts of river ice formation on stages in the lower river.”

As colder temperatures enter the basin, the Corps will closely monitor Missouri River ice conditions between the system reservoirs and downstream of Gavins Point Dam for potential ice jams that could impact river stages and water intakes.

Runoff in the upper Missouri River basin above Sioux City, Iowa, was 540,000 acre-feet during November, just 51 percent of average. The 2022 calendar year runoff forecast is 19.0 million acre-feet (maf.), 74 percent of average. The average annual runoff is 25.7 maf.

The total volume of water stored in the Missouri River mainstem reservoirs is currently 46 maf., which is 10.1 maf. below the base of the system flood control storage zone. System storage is forecast to begin the 2023 runoff season at 45.8 maf., which is 10.3 maf. below the base of the system flood control zone.

Mountain snowpack in the upper Missouri River Basin is accumulating at slightly-above average levels, the Corps said. About 25 percent of the mountain snowpack typically accumulates by December 1, and normally peaks near April 17. While the mountain snowpack is currently above average, it is too early in the season to make a projection of the final 2023 mountain snowpack. Additionally, plains snowpack in the upper Missouri River Basin is sparse, the Corps said.