Drought Persists In Upper Missouri River Basin
Drought conditions continue to affect the upper Missouri River basin above Sioux City, Iowa, according to the latest report by the Missouri River Water Management Division of the Northwest Engineer Division. July runoff in the upper basin was only 34 percent of average. July runoff above Fort Peck Dam was the lowest in 123 years of record-keeping.
Gavins Point Dam releases will be set to provide flow support at an intermediate service level, 1,500 cubic feet per second (cfs.) less than full service flow support at all four target locations (Sioux City, Omaha, Nebraska City, and Kansas City). Flow support volumes for the second half of the navigation season, as well as the navigation season length, are based on July 1 system storage. The flow support season length will be a full eight-month season, ending December 1 at the mouth of the Missouri River.
The updated 2021 upper basin runoff forecast is 14.6 million acre-feet (maf.), or 57 percent of average. If realized, this runoff amount would be the 10th driest year in the upper basin since 1898. System storage on August 1 was 53.9 maf., 2.2 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.
“Reservoir inflows in July have been declining due to the warmer and drier conditions in the upper basin,” said John Remus, chief of the Water Management Division. The Corps will evaluate lower Missouri River flow conditions to set Gavins Point releases to ensure that flows at the four downstream navigation target locations will be at or above the intermediate service level. The monthly study also 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.
Fall public meetings are currently scheduled to be held October 25–28 at several locations along the Missouri River. Locations and details will be announced in September.
Soil conditions in the upper basin are very dry. Drought conditions throughout the entire basin, particularly in the upper basin, worsened in July. According to the National Drought Mitigation Center, approximately 75 percent of the Missouri River basin is currently experiencing some form of abnormally dry or drought conditions, an increase of 10 percent since the end of June. The seasonal drought outlook, which extends through the end of September, shows that drought conditions will persist or expand across the upper basin.
Drought information can be viewed at: https://droughtmonitor.unl.edu/.