The US Army Corps of Engineers (Corps) reduced releases from Gavins Point Dam in late November to the winter release rate, marking the end of flow support for the 2016 navigation season. “Releases from Gavins Point Dam were reduced over a 3-day period from 25,000 cubic feet per second (cfs) to 18,000 cfs,” said Jody Farhat, Chief of the Missouri River Water Management Division. “Releases are expected to range between 17,000 cfs and 18,000 cfs this winter, but will be adjusted as needed to evacuate the remainder of water stored in the annual flood control zone prior to the start of the next year’s runoff season.” Based on the September 1 system storage, Gavins Point Dam winter releases will be at least 17,000 cfs. During the winter, the Corps will closely monitor conditions throughout the basin and will adjust releases to lessen the impact of river ice formation on water intakes along the lower river to the extent possible.

Runoff in the Missouri River Basin above Sioux City, Iowa, was 1.5 million acre-feet (MAF) during November, 141 percent of average. The 2016 calendar year runoff forecast is 24.3 MAF, 96 percent of average. Average annual runoff is 25.3 MAF. The total volume of water stored in the Missouri River Mainstem Reservoir System was 56.8 MAF as of November 30, occupying 0.7 MAF of the 16.3 MAF combined flood control storage zones.

Releases from Fort Peck were increased from 4,500 cfs to 7,000 cfs on December 5 and are expected to average 7,000 cfs to 8,000 cfs through February. Also on December 5, releases from Garrison were increased from 13,000 cfs to 16,000 cfs. Garrison’s releases are expected to average 16,000 cfs to 17,000 cfs this winter. Ice conditions will be monitored below Garrison and Oahe Dams throughout the winter, and releases will be adjusted as necessary. During the river freeze-in, releases from Garrison are typically set at 16,000 cfs to reduce the risk of ice-induced flooding in the Bismarck area. 

The comment period for the 2016-2017 Annual Operating Plan (AOP) ended November 11. The final AOP, which is expected to be completed in mid-December, will be posted on the Water Management website: http://www.nwd-mr.usace.army.mil/rcc.

The Corps will continue to monitor basin conditions, mountain snow and plains snow accumulation and adjust reservoir releases accordingly.

Reservoir Forecasts

Gavins Point Dam releases averaged 23,100 cfs during November. Releases were stepped down to the winter release rate of 18,000 cfs in late November. The Gavins Point reservoir ended November at elevation 1208.0 feet and will be lowered to near elevation 1207.5 feet during December.

Fort Randall Dam releases averaged 20,400 cfs in November. Releases will be adjusted as necessary to maintain the desired reservoir elevation at Gavins Point Dam. The reservoir ended November at elevation 1338.8 feet, falling 5.9 feet during the month. The reservoir may decline to near elevation 1337.5 feet in early December, before gradually rising, ending the month near 1339.5 feet. The reservoir is normally refilled during the winter to provide extra winter hydropower generation at Oahe and Big Bend Dams.

Big Bend Dam releases averaged 14,700 cfs in November. Releases are expected to average 16,800 cfs this month. The reservoir will remain near its normal elevation of 1420.0 feet during December.

Oahe Dam releases averaged 15,400 cfs during November. Releases are expected to average 16,200 cfs in December. The reservoir ended November at elevation 1609.0 feet, falling 0.6 feet during the month. The reservoir level is expected to fall slightly during December, ending the month near elevation 1608.7.

Garrison Dam releases averaged 13,100 cfs during the month. Releases were increased to 16,000 cfs in early December, and will remain at that rate through the month. Garrison reservoir ended November at elevation 1839.4 feet, rising 0.4 feet during the month. The reservoir level is expected to fall during December, ending the month near elevation 1838.6 feet.

Fort Peck Dam releases averaged 4,900 cfs during November and were increased to 7,000 cfs in early December. The reservoir ended November at elevation 2234.9 feet, up 0.1 feet during the month. The reservoir is expected to end December near elevation 2234.6 feet.

The forecasted 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 539 million kWh of electricity in November. Typical energy generation for November is 738 million kWh. The power plants are projected to generate 7.5 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