Omaha, Neb. — October runoff into the Missouri River basin above Sioux City, Iowa, was 2.8 million acre feet (MAF), more than two times normal and the second highest October runoff since recordkeeping began in 1898. October runoff in the Oahe and Fort Randall reaches were the first and second highest on record, respectively. As a result, the updated forecast for 2013 runoff is 25.9 MAF, 102 percent of normal. Normal annual runoff is 25.2 MAF.

“The upper basin has experienced a wet fall this year, with above normal rain and heavy snow in some areas in early October. This has resulted in wet soil conditions across much of Montana, Wyoming and the Dakotas,” said Mike Swenson, team leader in the Missouri River Basin Water Management office.

Due to the higher runoff, the total volume of water stored in the Missouri River Mainstem Reservoir System increased 0.4 MAF during October. “Despite 2013 runoff being normal, the impacts of the 2012 drought are still being felt at the largest three reservoirs - Fort Peck, Garrison, and Oahe. These three reservoirs are currently drawn down 3 to 10 feet below their desired levels,” said Swenson. “Our long-term studies indicate that we will likely begin the 2014 runoff season with system storage 4.6 MAF below the base of the annual flood control and multiple use zone.”  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.

“We will be paying close attention to the amount of mountain snowpack we receive in Montana and Wyoming as well as the plains snow accumulation in the Dakotas, this winter,” said Swenson. “We will know more about the potential impacts of the wet fall basin conditions by the start of the 2014 runoff season when we can factor actual on-the-ground conditions into our forecast models and we will include that information in our decision-making process.” 

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 that is 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:

Releases out of Gavins Point will be decreased to minimum winter levels during the third week in November. Based on the September 1 storage check, winter releases from Gavins Point will be scheduled at 12,000 cfs. “Temporary increases above 12,000 cfs will be provided during periods of ice formation to keep water intakes along the lower river operational. This winter’s anticipated release is slightly lower than last year’s actual release; however, with more normal tributary flows this fall we believe it is an obtainable goal. We will closely monitor river stages and maintain on-going coordination with water intake owners along the lower river as we reduce flows at the end of the navigation season.”  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.

Draft Annual Operating Plan public comment period closes Nov. 15

The Corps released the draft Annual Operating Plan in late September, and it is available on the Water Management Division’s website at:  http://www.nwd-mr.usace.army.mil/rcc/reports/pdfs/draftAOP2013-2014.pdf   

The five public meetings that had been scheduled throughout the basin Oct. 8–10 regarding the draft Annual Operating Plan (AOP) were cancelled due to the lapse of Federal appropriations. A conference call was held Oct. 28 to provide a brief overview on basin conditions and plans for regulating the reservoir system in 2014 followed by a question and answer session. As previously announced, the comment period will remain open until Nov. 15, and 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 30,000 cfs in October, averaging 27,200 cfs. Releases are expected to remain in that range through the third week of November, then be stepped down approximately 3,000 cfs each day until they reach 15,000 cfs. Releases will be held at that level for several days to allow water intake operators to assess river conditions at their location. Further reductions from 15,000 cfs to 12,000 cfs will be scheduled gradually in close coordination with the intake operators to ensure water supply is served to the extent reasonably possible. The reservoir behind Gavins Point Dam ended October 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 21,000 cfs to 29,000 cfs during October, averaging 25,800 cfs. Releases are expected to range from 26,000 cfs to 29,000 cfs during the first part of November. Releases will be stepped down near the end of November approximately one day prior to the Gavins Point reductions as necessary to maintain the elevation at Gavins Point. The reservoir ended October at elevation 1346.5 feet msl, down 6.7 feet during the month. The reservoir is expected to decrease 9 feet this month, ending November near elevation 1337.5 feet msl. The reservoir is normally drawn down to that elevation in the fall to provide space for winter hydropower generation at Oahe and Big Bend.

Big Bend releases averaged 15,300 cfs during the month of October. They are expected to average near 14,000 cfs this month. The reservoir will remain near its normal elevation of 1420 feet msl during November.

Oahe releases averaged 15,200 cfs during the month of October. Releases are expected to average near 14,000 cfs this month. The reservoir ended October at elevation 1602.0 feet msl, up 3.1 feet during the month. The reservoir is expected to rise about 1 foot during the month of November.

Garrison releases averaged 13,000 cfs in October. Releases are expected to remain at that rate during November then be increased to 16,000 cfs in early December. Garrison ended October at elevation 1,834.9 feet msl, up 0.5 foot from the end of September. It is expected to rise less than 1 foot during November.

Fort Peck releases average 5,000 cfs in October. Releases are expected to remain at that rate in November, before being increased to 6,500 cfs in early December. The reservoir ended October at elevation 2223.9 feet msl, down 0.3 feet from the previous month. The reservoir is forecast to drop less than 1 foot during November.

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 598 million kilowatt hours (kWh) of electricity in October. Typical energy generation for the month of October is 814 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 MAIN STEM RESERVOIR DATA  

                                     WATER RELEASES AND ENERGY GENERATION FOR OCTOBER

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