US Army Corps of Engineers
Northwestern Division

News Releases

Corps increases releases to lessen future flood risk

Published Sept. 4, 2014
The Missouri River Water Management office releases a report at the beginning of each month to the public documenting the monthly river forecast and release schedule. The Missouri River Water Management Division is part of the Northwestern Division of the U.S. Army Corps of Engineers and is located in Omaha, Nebraska.

The Missouri River Water Management office releases a report at the beginning of each month to the public documenting the monthly river forecast and release schedule. The Missouri River Water Management Division is part of the Northwestern Division of the U.S. Army Corps of Engineers and is located in Omaha, Nebraska.

Omaha, Neb. — The U.S. Army Corps of Engineers (Corps) Missouri River Basin Water Management Division is increasing releases at the four lower dams on the Missouri River following heavy rains in August.  The higher releases will evacuate flood water stored in the Mainstem Reservoir System preparing it to capture next year’s anticipated runoff, thus lessening potential future flood risk.  The excess water will also allow the Corps to extend the navigation season 10 days and provide higher winter releases, which will benefit winter hydropower generation and reduce risks to water intakes during periods of ice formation this winter. Runoff above Sioux City, Iowa in August was 3.2 million acre feet (MAF), 241 percent of normal.  The 2014 runoff forecast is 35.6 MAF, 141 percent of normal.  Average annual runoff is 25.2 MAF. 

“Rains in the upper basin have swelled tributary rivers and increased runoff into the reservoir system.  August runoff was the third highest since 1898,” said Jody Farhat, chief of the Missouri River Basin Water Management Division.  “The Corps’ reservoir system remains within normal operating levels, but the higher runoff has resulted in the need to evacuate water from the system this fall above the rate required for navigation.  Releases at the lower four projects, Oahe, Big Bend, Fort Randall and Gavins Point dams, which had been scheduled to meet full service navigation requirements downstream, will be increased to ensure the entire flood control capacity of the system is available for next year’s runoff.”  The total volume of water stored in the reservoir system is 61.3 MAF.  Currently, 5.2 MAF of the 16.3 MAF combined flood control storage is occupied. 

“Releases from Gavins Point Dam will be stepped up from the current release rate of 38,000 cubic feet per second (cfs) to 45,500 cfs during the next several days, and are expected to remain near that level throughout the fall.  By evacuating the excess water from the reservoir system at the lowest possible rate for the longest period of time, the updated release plan will properly prepare the reservoir system for next year’s runoff season, while reducing downstream flood risk this fall,” explained Farhat.  “Although releases are higher than normal for this time of year, flows are expected to remain in the channel unless we experience a significant amount of rain.”  The Corps will carefully monitor downstream conditions and adjust Gavins Point Dam releases as necessary this fall to provide flood risk reduction and continue evacuation of stored flood water. 

Based on the September 1 reservoir system storage, there will be a 10-day extension to the navigation season with Gavins Point winter releases of 20,000 cfs.  Navigation service at the mouth of the Missouri River will now end on December 10.  Both the longer navigation season and the higher winter release will better serve downstream water users during the remainder of the year.  Winter releases are normally near 17,000 cfs. 

The Corps will continue to monitor basin conditions and fine tune the regulation of the reservoir system based on the most up-to-date information. 

Draft Annual Operating Plan and Fall Public Meetings 

In late September, the Corps will post the 2014-2015 Draft Annual Operating Plan (AOP) for the Missouri River Mainstem Reservoir System on its website at http://www.nwd-mr.usace.army.mil/rcc/aop.html.  Fall public meetings will be held in five cities throughout the basin during the last week of October to discuss and take comments on the proposed operating plan.  The public meetings will include a presentation from the Corps regarding 2014 operations and plans for regulating the reservoir system in 2015, followed by a question and answer session.  Meeting times and locations will be announced in a future news release when additional details become available.  

Reservoir Forecasts  

Gavins Point Dam releases ranged from 28,000 cfs to 32,600 cfs in August, averaging 28,500 cfs.  Releases are expected to reach 45,500 cfs on September 9, and will be made from both the powerhouse and the spillway.  The reservoir behind Gavins Point Dam ended August at elevation 1206.9 feet, and will gradually rise to its normal seasonal pool elevation of 1207.5 feet in September. 

Fort Randall Dam releases averaged 27,900 cfs in August.  Fort Randall releases are expected to average 44,600 cfs in September, but will be adjusted as necessary to maintain the desired elevation at Gavins Point.  The planned fall release will require releases from the powerhouse and the outlet tunnels.  The reservoir ended August at elevation 1356.4 feet, up 0.3 feet during the month.  The reservoir is expected to end September near elevation 1353.5 feet.  The reservoir is normally drawn down to 1337.5 feet in the fall to provide space for winter hydropower generation at Oahe and Big Bend.  The annual drawdown will continue in October and November. 

Big Bend Dam releases averaged 25,300 cfs during the month of August.  They are expected to average 39,800 cfs this month, and all releases will be passed through the powerhouse.  The reservoir will remain near its normal elevation of 1420 feet during September. 

Oahe Dam releases averaged 28,000 cfs during the month of August.  Releases are expected to average 39,800 cfs this month.  Releases will be passed primarily through the powerhouse; however the outlet tunnels may be used on occasion during powerhouse maintenance this fall.  The reservoir ended August at elevation 1615.2 feet, up 1.5 feet during the month.  The reservoir is expected to drop nearly 2 feet during the month of September. 

Garrison Dam releases average 28,000 cfs in August. Releases were reduced from 28,000 cfs to 26,000 cfs in early September.  Releases will be reduced to 20,000 cfs later in the month.  Garrison ended August at elevation 1844.9 feet, down 1.2 feet from the end of July.  It is expected to drop 1 foot during September.  

Fort Peck Dam releases were reduced from 7,500 cfs to 6,000 cfs in late August, and averaged 7,300 cfs for the month.  Releases will be reduced from 6,000 cfs to 5,000 cfs in the middle of September.  The reservoir ended August at elevation 2232.2 feet, up 2.1 feet from the previous month.  The reservoir is forecast to rise less than 1 foot during September. 

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 962 million kilowatt hours (kWh) of electricity in August.  Typical energy generation for the month of August is 1,001 million kWh. The power plants are projected to generate 9.9 billion kWh of electricity this year, compared to the normal of 10 billion kWh. 

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.     

MISSOURI RIVER MAINSTEM RESERVOIR DATA  

 

Pool Elevation (feet above mean sea level)

Water in Storage - 1,000 acre-feet

 

On August 31

Change in August

On August 31

% of 1967-2013 Average

Change in August

Fort Peck

2232.2

+2.1

14,417

97

+439

Garrison

1844.9

-1.2

20,145

108

-437

Oahe

1615.2

+1.5

21,222

120

+525

Big Bend

1420.4

+0.3

1,656

97

+21

Fort Randall

1356.4

     +0.3

3,527

96

+26

Gavins Point

1206.9

+0.5

348

84

+12

 

 

 Total

61,315

108

+586

 

WATER RELEASES AND ENERGY GENERATION FOR AUGUST 

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

7.3

449

69

Garrison

28.0

1,719

275

Oahe

28.0

1,723

270

Big Bend

25.3

1,554

92

Fort Randall

27.9

1,714

184

Gavins Point

28.5

1,754

72

 

 

 Total

962

  

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Contact
Serena Baker
503-808-3710
serena.baker@usace.army.mil