Gavins Point Dam releases began the reduction to the winter release rate of 21,500 cubic feet per second (cfs) on December 4. “Based on the September 1 system storage, Gavins Point Dam winter releases will be at least 17,000 cfs. However, higher-than-normal runoff during the late summer and fall will allow us to provide a slightly higher release during the winter months. Higher winter releases will provide additional hydropower generation during the winter, which is one of the peak power demand periods. It will also benefit municipal and industrial water intakes below Gavins Point Dam, which can be impacted by low water levels during periods of ice formation,” said John Remus, chief of the U.S. Army Corps of Engineers’ (Corps) Missouri River Basin Water Management Division. Gavins Point Dam winter releases normally range between 12,000 and 17,000 cfs.

The total volume of water stored in the Missouri River mainstem reservoirs is currently 57.2 million acre-feet (MAF), occupying 1.1 MAF of the 16.3 MAF combined flood control storage zones according to the Corps. “System storage peaked on July 9 at 61.8 MAF and is declining, lowering 0.9 MAF in November. During the winter we will complete the evacuation of the system flood storage. At the beginning of next year’s runoff season the full 16.3 MAF of flood control capacity will be available to capture runoff from rainfall and snowmelt,” said Remus.

Runoff in the Missouri River Basin above Sioux City, Iowa, was 1.2 million acre-feet (MAF) during November, 110 percent of average. The 2017 calendar year runoff forecast is 29.4 MAF, 116 percent of average. Average annual runoff is 25.3 MAF. 

Releases from Fort Peck will be increased to 9,500 cfs in December and are expected remain at that rate through February. Releases from Garrison were increased from 15,000 cfs to 16,000 cfs on December 1. Releases will remain at that rate in early December, and conditions permitting, will be gradually increased to 23,500 cfs later in the winter. Prior to the river freeze-in, releases from Garrison are typically set near 16,000 cfs to reduce the risk of ice-induced flooding in the Bismarck area. As the colder, winter temperatures begin to enter the basin, river ice formation downstream of all the mainstem projects will be monitored and releases will be adjusted accordingly.

Weekly updates on basin conditions, reservoir levels and other topics of interest can be viewed here: https://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/weeklyupdate.pdf.

The comment period for the 2017-2018 Annual Operating Plan (AOP) ended November 17. The final AOP, which is expected to be completed in late December, will be posted on the Water Management website: https://www.nwd-mr.usace.army.mil/rcc.

The Corps will continue to monitor basin conditions, including plains and mountain snow accumulation, and will adjust the regulation of the System based on the most up-to-date information.

Reservoir Forecasts

Gavins Point Dam releases averaged 29,100 cfs during November. Releases are expected to average near 21,500 cfs during the winter but will be adjusted as necessary based on runoff and downstream river conditions. The Gavins Point reservoir ended November at elevation 1207.9 feet and will be near 1207.5 feet during the winter months.

Fort Randall Dam releases averaged 27,000 cfs in November. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point. The reservoir ended November at elevation 1338.3 feet and declined to near 1337.5 feet in early December. The reservoir will be refilled during the winter to increase winter hydropower generation at Oahe and Big Bend.

Big Bend Dam releases averaged 20,200 cfs in November. Releases are expected to average 22,000 cfs this month. The reservoir will remain near its normal elevation of 1420.0 feet during December.

Oahe Dam releases averaged 22,400 cfs during November. Releases are expected to average 21,800 cfs in December. The reservoir ended November at elevation 1608.2 feet, falling 1.7 foot during the month. The reservoir level is expected to decline approximately another 0.6 feet during December.

Garrison Dam releases averaged 15,100 cfs for the month. Releases were increased to 16,000 cfs in December and will be increased to near 23,500 cfs during the winter, river conditions permitting. Garrison reservoir ended November at elevation 1841.2 feet, declining 0.1 foot during the month. The reservoir level is expected to decline 1.1 feet during December, ending the month near elevation 1840.1 feet.

Fort Peck Dam releases averaged 6,000 cfs during November. Releases will be increased to 9,500 cfs in mid-December. The reservoir ended November at elevation 2236.0 feet, declining 0.4 foot during the month. The reservoir is expected to fall approximately 0.9 foot during December ending the month near elevation 2235.1 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 703 million kWh of electricity in November. Typical energy generation for November is 734 million kWh. The power plants are projected to generate 9.6 billion kWh of electricity this year, compared to the long-term average of 9.3 billion kWh.

To view the detailed three-week release forecast for the mainstem dams, go to https://www.nwd-mr.usace.army.mil/rcc/reports/twregfcast.pdf.

MISSOURI RIVER MAINSTEM RESERVOIR DATA

WATER RELEASES AND ENERGY GENERATION FOR NOVEMBER