Missouri River Conditions Improving, But Drought Persists

While the Missouri River basin has seen improved runoff for two consecutive months, it is not enough to overcome the long-term drought persisting in much of the basin, the Corps of Engineers reported August 3.

July runoff in the Missouri River basin above Sioux City, Iowa, was 3.2 million acre-feet (maf.), which is 98 percent of average and 0.7 maf. more than was forecast last month. As a result, the Corps raised its annual runoff forecast of 20.6 maf., which is 80 percent of average and 0.6 maf. higher than last month’s forecast.

“As expected, reservoir inflows in July have been declining due to the warmer and drier conditions in the upper Missouri River Basin,” said John Remus, chief of the Corps’ Missouri River Basin Water Management Division. “Per the July 1 system storage check, navigation support was increased slightly to 500 cubic feet per second above minimum service levels. The navigation support season will be three days shorter than normal per the guidance in the Master Manual.”

The Corps will evaluate lower Missouri River flow conditions to set Gavins Point Dam releases to ensure that flows at the four downstream navigation target locations will be at or above the target levels.

“The monthly study indicates that the winter release from Gavins Point, which is based on the September 1 system storage check, will likely be at a minimum rate of 12,000 cfs.,” Remus said.

System storage peaked on July 20 at 52.1 maf. System storage on August 1 was 51.8 maf., 4.3 maf. below the base of the Annual Flood Control and Multiple Use Zone. “System storage is expected to continue to decline further into the Carryover Multiple Use Zone during the remainder of 2022 as we make releases during the drier summer and fall periods to meet the authorized purposes,” Remus said.

According to the National Drought Mitigation Center, approximately 62 percent of the Missouri River basin is currently experiencing some form of abnormally dry or drought conditions, with 6 percent being extreme or exceptional drought. The seasonal drought outlook, which extends through the end of October, shows drought conditions will persist and expand across the lower basin.