Missouri River Runoff Improves, But Drought Remains
The month of June brought heavy rainfall in the upper Yellowstone River basin, which improved—but did not eliminate—drought conditions in the overall Missouri River basin, the Corps of Engineers reports.
Under the terms of the Missouri River Mainstem System Master Water Control Manual—or Master Manual for short—the Corps measures the water storage in the entire Missouri River reservoir system each July 1 and uses that information to determine the level of support for navigation for the remainder of the navigation season.
This year, that means that the navigation flow support service level will be increased slightly, and the navigation season will be shortened by three days, said John Remus, chief of the Corps’ Missouri River Basin Water Management Division.
Specifically, releases from Gavins Point Dam, the lowest dam in the reservoir system, will be set to provide navigation flow support at a level 500 cfs. above minimum-service at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City). Flow targets may be missed to conserve water if there is no commercial navigation in a given reach, the Corps said.
The Corps reported that June runoff above Sioux City, Iowa, was 5.2 million acre-feet (maf.), 94 percent of average. The updated 2022 runoff forecast is 20.0 maf., 78 percent of average and 1.7 maf. higher than last month’s forecast.
“Heavy rain in mid-June on the upper Yellowstone River coincided with mountain snowmelt increasing inflows into Garrison reservoir,” Remus said.
Runoff into the Garrison reservoir was 110 percent of average. The only other reach above average was Gavins Point to Sioux City, which was 136 percent of average.
“While soil moisture has improved in some areas over the last month, drought conditions persist across much of the Missouri River basin, and mainstem reservoir levels remain below normal,” Remus said.
Due to the ongoing drought and the amount of water stored in the reservoir system, water conservation measures will likely continue through the remainder of 2022 and into 2023, the Corps said. The winter release rate from Gavins Point, which is based on the September 1 storage check, will likely be at a minimum rate of 12,000 cfs.
