Drought Triggers Missouri River Conservation Measures
The ongoing drought in the Upper Midwest has triggered water conservation measures, the Corps of Engineers’ Missouri River Water management team announced July 8. Very dry conditions resulted in reduced flows for the second half of the navigation flow support season, based on the July 1 Missouri River Mainstem Reservoir System storage, in accordance with guidelines outlined in the Master Manual.
Very dry conditions continue to affect the upper Missouri River basin above Sioux City, Iowa—despite recent heavy rainfall in the lower basin—resulting in June runoff in the upper basin only 52 percent of average.
The updated 2021 upper basin runoff forecast is 15.6 million acre-feet (maf.), about 60 percent of average. If realized, this runoff amount would be the 10th driest year in the upper basin since 1898. System storage on July 1 was 55.2 maf., 0.9 maf. below the base of the Annual Flood Control and Multiple Use Zone. System storage is expected to decline further into the Carryover Multiple Use Zone during the remainder of 2021.
“We reduced the service level to support navigation by 1,500 cubic feet per second (cfs.) from the full-service level,” said John Remus, chief of the Corps of Engineers’ Missouri River Basin Water Management Division. “This intermediate service level will be maintained through the end of the navigation flow support season, which will end on December 1 at the mouth of the Missouri. The intermediate service level is a necessary water conservation measure to ensure that authorized purposes will be served in the short and long term,” Remus said
The Gavins Point release was reduced from 30,500 cfs. to 28,500 cfs. on July 1 in accordance with the reduced service level. The Corps will evaluate lower Missouri River flow conditions daily to set Gavins Point releases to ensure that flows at the four downstream navigation target locations will be at or above the reduced service level. The monthly study also indicates that the winter release from Gavins Point, based on the September 1 storage check, will likely be at a minimum rate of 12,000 cfs.