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Garrison releases will increase to 60,000 CFS to address recent rainfall
OMAHA, NE – The U.S. Army Corps of Engineers Missouri River Basin Water Management Division has announced plans to make additional release increases from Garrison Dam. “Releases are being stepped up from 52,000 cfs to 60,000 cfs,” said John Remus, Chief of the Missouri River Basin Water Management Division. “Releases will be increased over 3 days, reaching the 60,000 cfs rate on June 23.” The Garrison reservoir is currently at 1851.6 feet, 1.4 feet into the Exclusive Flood Control Zone, which extends from elevation 1850 to 1854 feet. The reservoir is expected to peak near elevation 1852.4 feet in the next two weeks as runoff from the remaining mountain snowpack tapers off. The maximum power plant release is 41,000 cfs, therefore, releases are being made from both the powerhouse and the regulating tunnels. The 60,000 cfs release rate is expected to continue into mid-July. The 60,000 cfs release will result in a river stage increase near Bismarck of approximately 1.5 feet, from 11.5 feet to about 13.0 feet. Flood stage at Bismarck is 14.5 feet.
- Garrison releases are being increased due to persistent rains in the reach from Fort Peck to Garrison. “Widespread rains across much of the Missouri River Basin have increased inflows into the System dams and have also increased flows on tributaries downstream of the System,” said John Remus, Chief of the Missouri River Basin Water Management Division.
- Fort Peck Dam releases are being maintained at 20,000 cfs. The release is in excess of the powerplant capacity so releases are being made from both the powerhouse and spillway. The reservoir is currently at elevation 2246 feet, the base of the Exclusive Flood Control Zone, which extends from elevation 2246 to 2250 feet. The reservoir is expected to peak near elevation 2247.4 feet in the next two weeks.
- Gavins Point releases were reduced from 44,000 to 36,000 cfs this week due to high flows downstream of the Missouri River mainstem reservoir system (System). Releases are adjusted, when needed, in order to lessen flooding downstream of all the System projects. It is important to note that the ability to significantly reduce flood risk along the lower Missouri River diminishes at locations further downstream due to the large uncontrolled drainage area and the travel time from Gavins Point Dam.
System storage is currently 65.7 MAF, occupying 9.6 MAF of the 16.3 MAF flood control zone. “About 40 percent of the System’s flood storage remains available to capture runoff,” said Remus. System storage is expected to peak in mid-July.
The mountain snowpack peaked April 19 in the Fort Peck reach and on April 15 in the Fort Peck to Garrison reach. As of June 20, both reaches have 1.5 inches or less of snow water equivalent remaining. View the mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf.
Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/weeklyupdate.pdf.
To view the detailed three-week release forecast for the mainstem dams, go to http://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf.
For river stage information, go to https://www.weather.gov/mbrfc/.
The Corps will continue to monitor basin and river conditions, including rainfall and mountain snowmelt, and will adjust the regulation of the System based on the most up-to-date information.
Release no. 18-038