Winter Gavins Point releases will be at minimum rates
Drought conditions, particularly in the Missouri River Basin above Sioux City, Iowa (upper Basin), are persisting. Per the Master Manual and the Sept. 1 System storage check, winter releases from Gavins Point Dam will be 12,000 cubic feet per second, as part of the overall water conservation measures.
“Reservoir inflows in August were much lower than average. We expect below-average inflows into the System through the rest of 2021,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division.
“Several significant rainfall events occurred in August. In response, the Corps reduced Gavins Point releases 4,000 cfs as tributary flows downstream of the System increased. As the tributary runoff subsides, the Gavins Point releases will be adjusted to meet navigation flow targets,” added Remus.
Despite localized heavy rainfall events throughout the basin during August, drought conditions expanded across the basin due to the exceptionally dry soils. August runoff in the upper Basin was 54% of average. The 2021 calendar year forecast for the upper Basin, updated on Sept. 1, is 14.7 million acre-feet (MAF), 57% of average. Average annual runoff for the upper Basin is 25.8 MAF.
As of Sept. 2, the total volume of water stored in the System was 52.1 MAF, which is 4.0 MAF below the base of the System’s flood control zone. System storage is expected to continue to decline through the fall. Updated reservoir studies indicate that System storage is expected to be more than 8.0 MAF below the base of flood control at the start of the 2022 runoff season.
According to the National Drought Mitigation Center, drought degradation is occurring across much of the upper Basin. As of Sept. 2, approximately 83% of the Missouri River basin is experiencing some form of abnormally dry conditions or drought. The seasonal drought outlook, which extends through the end of November, shows drought conditions persisting across most of the upper Basin.
The July 1 System storage check indicated navigation flow support for the second half of the season (July 1 to Dec. 1) would be at 1,500 cfs below the full-service level for a full 8-month-long season. Gavins Point releases will be reduced in a stair-step manner to winter release rates around Nov. 22.
Fort Peck and Garrison Fall Release Reduction
Fort Peck and Garrison releases will be reduced to their fall rates in mid-September. Beginning Sept. 6, Fort Peck release will be stepped down from 9,500 cfs to 5,000 cfs. The release reduction will result in a Missouri River stage reduction of about 2.5 feet at Wolf Point and Culbertson, Montana. The Garrison release will be reduced from 21,000 cfs to 20,000 cfs on Sept. 6 and then stepped down to 13,500 cfs in mid-September. The release reduction from 21,000 cfs to 13,500 cfs will result in a Missouri River stage reduction of about 2 feet at Bismarck, North Dakota.
Winter Release Rate
As per criteria in the Master Manual, the winter release rate is determined based on the Sept. 1 System storage. Per the Sept. 1 System storage, winter releases from Gavins Point Dam will be at the minimum rate of 12,000 cfs. In anticipation of the low winter releases, a letter was sent on Sept. 1 to all water users below Gavins Point dam making them aware of the planned releases and encouraging them to assess the risk to their facilities.
Monthly Water Management Conference Calls
The are no more scheduled monthly water management call for 2021. The monthly calls will resume in January 2022. Typically, water management calls include an update from the National Weather Service’s Missouri Basin River Forecast Center, and an update on the Missouri River mainstem reservoir system operations. The last call for 2021 was held on Thursday, August 5. All calls are recorded in their entirety and are available to the public on the Defense Video and Imagery Distribution System at www.dvidshub.net/unit/usace-nwd.
Fall Public Meetings
Fall public meetings will be held the week of October 25-28. The meeting at Nebraska City will be Wednesday, Oct. 27 at 6 p.m. at Steinhart Lodge, 121 N Steinhart Park Road.