As part of the normal operation of the Mainstem Reservoir System, the U.S. Army Corps of Engineers (Corps) Missouri River Basin Water Management Division has reduced releases from several Missouri River dams to winter levels. 

Due to robust runoff in the Missouri River basin this year, flow support for navigation was extended 10-days, ending on Dec. 10 at the mouth.  “Daily releases from Fort Randall and Gavins Point dams were reduced to normal winter levels in a stair-step manner between Dec. 1 and 8 marking the end of the 2014 navigation flow support,” says Jody Farhat, chief of the Missouri River Basin Water Management Division. “Our reservoir release plans during the winter will provide good service to downstream water users and ensure we have the entire flood control capacity available next year.”

The 2014 calendar year runoff forecast is 34.5 million acre feet (MAF), 137 percent of normal.  Average annual runoff is 25.2 MAF.  Runoff during the month of November was 83 percent of normal due in part to cold weather freezing many of the tributaries, which reduced inflow into the reservoir system.  The total volume of water stored in the reservoir system at the end of November was 56.5 MAF, down 1.6 MAF for the month. Currently, less than 0.5 MAF of the 16.3 MAF combined flood control storage is occupied.  The remaining stored flood waters will be evacuated during the winter, and all flood control storage will be available by the start of the 2015 runoff season.

During the winter, the Corps will closely monitor conditions throughout the basin and make reservoir regulation adjustments to lessen the impact of river ice formation.  In late November, releases from Garrison Dam were reduced to 16,000 cfs in anticipation of ice formation. Garrison releases will remain at this level in December, and conditions permitting, will increase to 19,500 cfs in January.