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Posted 10/8/2013

Release no. 20131008-001


Contact
Michael Coffey
503-808-3722
michael.a.coffey@usace.army.mil

Omaha, Neb. — Despite two months of higher than normal precipitation in portions of the upper Missouri River Basin, dry soil conditions have resulted in near normal runoff during this period. Thus, the Corps will continue to implement measures to conserve water in the Mainstem Reservoir System. Runoff in the Missouri River Basin above Sioux City, Iowa, during the month of September was slightly below normal (91 percent of normal). The calendar year runoff forecast also remains below normal at 23.2 million acre feet (maf), 92 percent of normal.

“Reservoir levels at the upper three large reservoirs, Fort Peck, Garrison and Oahe, are 4 to 10 feet below their desired elevations,” said Jody Farhat, Chief of the Missouri River Basin Water Management office. The total volume of water stored in the Missouri River Mainstem Reservoir System declined by 1.2 maf this past month. System storage on Oct. 1 was 51.0 maf, down from 52.2 maf on Sept.1, and 5.1 maf below the base of the annual flood control and multiple use zone. The base of the flood control and multiple use zone is 56.1 maf. The annual flood control pool is the desired operating zone for the system because it allows the Corps to fully serve all eight congressionally authorized purposes.

Based on the July 1 storage check, the Corps is providing a full, 8-month navigation season (April 1 to Dec. 1) and reduced flow support in accordance with the Master Manual, the water control plan used by the Corps to regulate the system. Flow support for navigation during the second half of the season increased 3,000 cfs from the minimum service level provided in the first half of the season. Full service level is 6,000 cfs above the minimum service level. Minimum service flow support is generally sufficient to provide a navigation channel 8 feet deep by 200 feet wide, and full service flow support provides a navigation channel 9 feet deep and 300 feet wide. The navigation season’s normal start and end dates by location along the river are indicated below:

 


Normal Navigation Season Start/End Dates

 Location

 Start

 End

 Sioux City, Iowa

 March 23

 Nov. 22

  Omaha, Neb.

 March 23

 Nov. 24

 Nebraska City, Neb.

March 23

 Nov. 25

 Kansas City, Mo.

March 28

 Nov. 27

 Mouth near St. Louis, Mo.

April 1

 Dec. 1

Based on the Sept. 1 storage check, drought conservation measures will again be implemented this winter. “Winter releases from Gavins Point will be at minimum levels, averaging near 12,000 cfs from December through February. Temporary increases above 12,000 cfs will be provided during periods of ice formation to keep water intakes along the lower river operational.” When the reservoir system is full, Gavins Point winter releases are generally scheduled near 17,000 cfs, or higher if flood water is being evacuated.

The above normal fall precipitation has resulted in improved soil moisture conditions, especially in the western portion of the basin. 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

The Corps released the draft Annual Operating Plan (AOP) in late September; it is now available on the Water Management Division’s website at:  http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/draftAOP2013-2014.pdf. The 2013-2014 Draft Annual Operating Plan anticipates low, relatively stable runoff into the basin for the remainder of the 2013 calendar year and into early spring 2014. As a result, the Corps expects system storage to be below the base of the annual flood control pool at the start of the 2014 runoff season, which begins on or around March 1, near the same level it was at the start of the 2013 runoff season.

“All scenarios in the Draft AOP indicate reduced flow support to start next year’s navigation season,” said Farhat. “If runoff volumes in the upper basin are near normal or below normal, reduced flow support would continue during the second half of the 2014 navigation season, and there is also the potential for a shortening of the navigation season length. Under these conditions, minimum winter releases would be likely in the winter of 2014-2015.”  If runoff levels are above normal, as indicated in the draft AOP runoff scenarios, full navigation support for the second half of the season would be provided, as well as a 10-day extension of the navigation season.”

The five public meetings that were scheduled throughout the basin Oct. 8-10 regarding the draft Annual Operating Plan (AOP) were cancelled due to the lapse of Federal appropriations. There are no plans to reschedule the meetings; however, once the lapse in appropriations has been resolved, a conference call will be scheduled to take comments and answer questions. Details will be provided in a news release and posted on the Corps website when available. As previously announced, the comment period will remain open until Nov. 15; the final AOP will be released in December. Comments may be emailed through the “Contact Us” link on the website, or mailed to the address below:

U.S. Army Corps of Engineers, Northwestern Division

Attn: Missouri River Water Management

1616 Capitol Ave, Suite 365

Omaha, NE 68102

Reservoir Forecasts

Gavins Point releases ranged from 23,000 cfs to 33,000 cfs in September, averaging 30,300 cfs. Releases are expected to remain in that range through mid-November when they will be gradually be decreased to the winter release rate by early December. The reservoir behind Gavins Point Dam ended September at elevation 1207.7 feet msl. The reservoir will remain near its normal fall pool elevation of 1207.5 feet msl in October.

Fort Randall releases ranged from 23,000 cfs to 35,000 cfs during September, averaging 30,300 cfs. Releases will be adjusted during October as necessary to maintain the desired elevation at Gavins Point. The reservoir ended September at elevation 1353.2 feet msl, down 2.2 feet during the month. The reservoir is expected to decrease 8 feet this month, ending October near elevation 1345.0 feet msl. The reservoir is normally drawn down to 1337.5 feet msl in the fall to provide space for winter hydropower generation at Oahe and Big Bend. The annual drawdown will continue through the end of November.

Big Bend releases averaged 25,700 cfs during the month of August. They are expected to average near 17,000 cfs this month. The reservoir will remain near its normal elevation of 1420 feet msl during October.

Oahe releases averaged 29,200 cfs during the month of September. Releases are expected to average near 17,000 cfs this month. The reservoir ended September at elevation 1598.9.5 feet msl, down 2.6 feet during the month. The reservoir is expected to drop about 1 foot during the month of October.

Garrison releases were reduced from 19,000 cfs to 13,000 cfs during September, averaging 16,300 cfs for the month. Releases will remain at 13,000 cfs during October and November, before being increased to 16,000 cfs in early December. Garrison ended September at elevation 1,833.9 feet msl, down 0.7 foot from the end of August. It is expected to drop less than 1 foot during October.

Fort Peck releases were reduced from 8,000 cfs to 5,000 cfs during September. Releases will remain at 5,000 cfs during October and November, before being increased to 6,500 cfs in early December. The reservoir ended September at elevation 2224.2 feet msl, down 0.9 feet from the previous month. The reservoir is forecast to drop less than 1 foot during October.

The forecast reservoir releases and elevations discussed above should not be assumed to be definitive. Additional precipitation or lack of precipitation in the basin could cause adjustments to the reservoir release rates.

The six mainstem power plants generated 812 million kilowatt hours (kWh) of electricity in September. Typical energy generation for the month of September is 897 million kWh. The power plants are projected to generate 7.5 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  (ft msl)

Water in Storage - 1,000 acre-feet

 

On September 30

Change in September

On September 30

% of 1967-2012 Average

Change in September

Fort Peck

2224.2

-0.9

12,846

88

-171

Garrison

1833.9

-0.7

16,678

91

-188

Oahe

1598.9

-2.6

16,157

94

-703

Big Bend

1420.8

+0.8

1,670

98

+53

Fort Randall

1353.2

      -2.2

3,256

97

-187

Gavins Point

1207.7

+1.3

367

87

+33

 

 

 

50,974

92

-1,163

 

WATER RELEASES AND ENERGY GENERATION FOR SEPTEMBER

 

 

Average Release in 1,000 cfs

Releases in 1,000 af

Generation in 1,000 MWh

Fort Peck

6.4

379

62

Garrison

16.3

972

146

Oahe

29.0

1,728

250

Big Bend

25.7

1,529

91

Fort Randall

30.3

1,801

187

Gavins Point

30.5

1,814

77

 

 

 

812

###

Annual Operating Plan Master Manual Missouri River Water Management