Gavins Point releases to remain steady through August
Below-normal precipitation in Montana and Wyoming during July resulted in slightly below-average July runoff in the upper Basin. The 2020 calendar year upper basin runoff forecast, updated on Aug. 3, is 30.9 million acre-feet (MAF), 120 percent of average. Average annual runoff for the upper basin is 25.8 MAF.
“Reservoir inflows in July have been declining due to the warmer and drier conditions in the upper Basin. The 2020 calendar year runoff forecast has been reduced slightly, due to this declining inflow in July; however, the runoff forecast still remains above average due to wet soil conditions in North Dakota and South Dakota, and the increased long term chance for precipitation indicated by the National Weather Service’s climate outlook,” said John Remus, chief of the U.S. Army Corps of Engineers’ Missouri River Basin Water Management Division. “We plan to maintain Gavins Point Dam releases at 30,000 cfs through August,” Remus added.
As of Aug. 5, the total volume of water stored in the System was 61.5 MAF, occupying 5.4 MAF of the System’s 16.3-MAF flood control zone. System storage peaked at 61.8 MAF on July 16, and is forecast to continue to decline through the fall and winter so all 16.3 MAF of flood control storage is available prior to the start of the 2021 runoff season.
Soils continue to dry out in the upper Missouri River Basin due to below-normal precipitation and warmer-than-normal temperatures in Montana and Wyoming. Drought conditions, based on the National Drought Mitigation Center Drought Monitor, have intensified in areas of both the upper Basin and the lower Basin.
The July 1 System storage check indicated flow support for the second half of the navigation season would be at least at the full service level for a full-length season. Full service flow support is designed to provide a 9-feet deep by 300-foot wide navigation channel from Sioux City, Iowa, to the mouth of the river near St. Louis, Missouri. Flow support is normally provided for an 8-month season from April 1 through December 1 at the mouth.
Fort Peck Release Rate
Due to continued hydropower unit testing and the lower runoff forecast for the reservoir basin above Fort Peck, the release rate from Fort Peck will remain at 9,000 cfs in August.
Winter Release Rate
The winter release rate is determined based on the Sept. 1 System storage. Per the Aug.1 monthly studies and the expected Sept. 1 System storage, winter releases from Gavins Point Dam will be at least 17,000 cfs.
The mountain snowpack in the reaches above Fort Peck and from Fort Peck to Garrison melted by early July. The mountain snowpack peaked in both reaches: on April 16 in the Fort Peck reach at 109% of average and on April 19 in the Fort Peck to Garrison reach at 112 percent of average. The mountain snowpack graphics can be viewed here: https://go.usa.gov/xE6wT.
Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: https://go.usa.gov/xE6wa.
Monthly Water Management Conference Calls
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 scheduled call for 2020 was held on Thursday, June 4. These monthly calls will resume in January 2021. 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.
2019 Summary of Actual Regulation
The Summary of Actual 2019 Regulation of the Missouri River Mainstem Reservoir System Summary is available here: https://go.usa.gov/xwWTY. This document contains a summary of the actual regulation of the Missouri River Mainstem Reservoir System for the 2019 calendar year.
Gavins Point Dam
Average releases past month – 30,600 cfs
Current release rate – 30,000 cfs (as of August 1)
Forecast release rate – 30,000 cfs (month of August)
End-of-July reservoir level – 1207.4 feet
Forecast end-of-August reservoir level – 1206.5 feet
Notes: Releases may be adjusted as necessary to offset tributary flows from heavy rain events.
Fort Randall Dam
Average releases past month – 27,200 cfs
End-of-July reservoir level – 1357.9 feet
Forecast end-of-August reservoir level – 1355.6 feet
Notes: Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point.
Big Bend Dam
Average releases past month – 27,900 cfs
Forecast average release rate – 23,600 cfs
Forecast reservoir level – 1420.9 feet
Average releases past month – 27,300 cfs
Forecast average release rate – 24,500 cfs
End-of-July reservoir level – 1612.3 feet
Forecast end-of-August reservoir level – 1612.5 feet
Average releases past month – 28,000 cfs
Current release rate – 28,000 cfs
Forecast average release rate – reduce to 26,000 cfs on 9 August
End-of-July reservoir level – 1843.5 feet
Forecast end-of-August reservoir level – 1841.6 feet
Fort Peck Dam
Average releases past month – 10,500 cfs
Current release rate – 8,500 cfs
Forecast average release rate – 9,000 cfs
End-of-July reservoir level – 2240.1 feet
Forecast end-of-August reservoir level – 2239.8 feet
The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other circumstances could cause adjustments to the reservoir release rates.
The six mainstem power plants generated 977 million kWh of electricity in July. Typical energy generation for July is 961 million kWh. The power plants are projected to generate 10.4 billion kWh of electricity this year, compared to the long-term average of 9.4 billion kWh.
To view the detailed three-week release forecast for the mainstem dams, go to http://go.usa.gov/xVgWr.