US Army Corps of Engineers
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Corps maintains high releases to reduce future flood risk

Published Oct. 8, 2014

Omaha, Neb. — The U.S. Army Corps of Engineers (Corps) Missouri River Basin Water Management Division is maintaining above normal releases at the four lower dams on the Missouri River. As expected, September runoff above Sioux City, Iowa, remained well above normal, totaling 1.8 million acre feet (MAF), 157 percent of normal. The 2014 runoff forecast is 35.5 MAF, 141 percent of normal, down slightly from one month ago. Average annual runoff is 25.2 MAF.

Higher releases now from Oahe, Big Bend, Fort Randall, and Gavins Point dams will evacuate flood water stored in the Mainstem Reservoir System, thus reducing our future flood risk,” says Jody Farhat, chief of the Missouri River Basin Water Management Division. “Higher releases will ensure we have the entire flood control capacity available next year.”

The excess water also will allow the Corps to extend the navigation season and provide higher winter releases, which will benefit winter hydropower generation and reduce risks to water intakes during periods of ice formation this winter. Navigation service at the mouth of the Missouri River will now end on December 10. Gavins Point winter releases, which are normally near 17,000 cfs, will be scheduled at 20,000 cfs from December through February. The longer navigation season and the higher winter release will better serve downstream water users during the remainder of the year.

The total volume of water stored in the reservoir system at the end of September was 60.0 MAF, down 1.4 MAF for the month. Currently, 3.9 MAF of the 16.3 MAF combined flood control storage is occupied. “Due to wetter than normal conditions in the upper basin, runoff is expected to remain high for the rest of the year,” adds Farhat. “And, that additional runoff is already built into our planned operation of the reservoir system.”

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.

Reservoir Forecasts

Gavins Point Dam releases were increased from 33,000 to 45,500 cubic feet per second (cfs) in early September, averaging 43,600 cfs for the month. Releases will continue near 45,500 cfs through October, and will be made through the powerhouse and spillway. The reservoir behind Gavins Point Dam ended September at elevation 1206.3 feet, and will gradually rise to its normal seasonal pool elevation of 1207.5 feet later this fall.

Fort Randall Dam releases averaged 44,500 cfs in September. Fort Randall releases 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 September at elevation 1351.4 feet, down 5 feet during the month. The reservoir is expected to end October near elevation 1345.0 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 dams. The annual drawdown will continue in November.

Big Bend Dam releases averaged 34,800 cfs during the month of September. They are expected to average 36,600 cfs this month, and all releases will be made through the powerhouse. The reservoir will remain near its normal elevation of 1420 feet during October.

Oahe Dam releases averaged 38,200 cfs during the month of September. Releases are expected to average 36,500 cfs this month. Releases will be passed primarily through the powerhouse; however, the outlet tunnels may be used on occasion during powerhouse maintenance, as was done during late September. The reservoir ended September at elevation 1613.0 feet, down 2.2 feet during the month. The reservoir is expected to drop more than 2 feet during the month of October.

Garrison Dam releases were reduced from 28,000 to 24,000 cfs during September, averaging 24,800 cfs for the month. Releases will be reduced from 24,000 to 20,000 cfs in early October. The reservoir behind Garrison ended September at elevation 1844.1 feet, down 0.8 feet during the month. It is expected to drop 1 foot during October.

Fort Peck Dam releases were reduced from 6,500 to 5,000 cfs during September, averaging 5,400 cfs for the month. Releases will remain near 5,000 cfs in October. The reservoir ended September at elevation 2232.6 feet, up 0.4 feet from the previous month. The reservoir is forecast to rise less than 1 foot during October.

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 1,043 million kilowatt hours (kWh) of electricity in September. Typical energy generation for the month of September is 894 million kWh. The power plants are projected to generate 9.8 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 September 30

Change in September

On September 30

% of 1967–2013 Average

Change in September

Fort Peck

2232.6

+0.4

14,502

98

+85

Garrison

1844.1

-0.8

19,875

109

-270

Oahe

1613.0

-2.2

20,478

119

-744

Big Bend

1420.6

+0.2

1,664

98

+9

Fort Randall

1351.4

-5.0

3,108

93

-419

Gavins Point

1206.3

-0.6

334

79

-14

 

 

 Total

59,961

108

-1,354

 

 WATER RELEASES AND ENERGY GENERATION FOR SEPTEMBER

 

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

5.4

323

50

Garrison

24.8

1,477

235

Oahe

38.2

2,272

345

Big Bend

34.8

2,069

124

Fort Randall

44.5

2,650

210

Gavins Point

43.7

2,598

79

 

 

Total

1043

Draft Annual Operating Plan and Fall Public Meetings

The Missouri River Basin Water Management Division will hold five public meetings in late October to discuss the draft 2014–2015 Annual Operating Plan (AOP) for the Missouri River Mainstem Reservoir System. The public meetings will include a presentation from the Corps regarding 2014 operations and plans for managing the reservoir system in 2015, followed by a question and answer session. There also will be an opportunity for members of the public and stakeholders to speak one-on-one with Corps officials. Meetings are scheduled at Fort Peck, Mont., on October 27; Bismarck, N.D., and Pierre, S.D., on October 28; and Smithville, Mo., and Council Bluffs, Iowa, on October 29. A complete list of meeting locations and times can be found at the following website: http://www.nwd.usace.army.mil/Media/NewsReleases/tabid/1989/Article/503066/corps-invites-public-to-missouri-river-operations-meetings.aspx    

Comments on the draft AOP will be taken during the series of public meetings. Written and email comments will be accepted through November 21, 2014. Email comments should be sent to the following: Missouri.Water.Management@nwd02.usace.army.mil. The 2014–2015 draft Annual Operating Plan is available online: http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/draftAOP2014-2015.pdf.

 

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Release no. NR20141008-MRWM