OMAHA, Neb. — At the height of the Flood of 2011, 16 million acre feet of flood water was stored in the Missouri River Mainstem system. Since storage peaked on July 1, the Corps has evacuated 15.4 million acre feet of floodwater and is on track to discharge the remainder by the start of the 2012 runoff season.

The Corps continues to maintain a flexible stance with its reservoir release rates into the winter and intends to maintain that stance this spring, said Jody Farhat, Chief of the Water Management Division.

Initial plans were to reduce releases to 20,000 cubic feet per second out of Gavins Point Dam beginning Dec. 1. In an attempt to increase the amount of flood control storage going into next year’s runoff season, the Corps will maintain a release of 40,000 cfs out of the reservoir through Dec. 7.

“This adjustment in combination with other management actions could potentially provide us with an additional 500,000 cfs of storage in the system by the start of the runoff season,” said Farhat. “That number is based on current conditions and the weather situation we are looking at today. It’s very early, and the situation could change quickly throughout the winter, but we’re being proactive in the hopes to start the runoff year with some additional storage in the system.”

In contrast to last year, precipitation has been below normal over most of the basin this fall, said Farhat. However, it is too early to tell what will materialize during the winter and spring, she said. Very little snow has accumulated on the northern plains to date.

Beginning Dec. 8, the Water Management team plans to begin decreasing releases by 3,000 cfs per day until a release rate of 20,000 cfs is reached. Farhat said the team will continue to monitor weather conditions and may consider extending the 40,000 cfs release out of Gavins Point if the weather allows.

“We will continue to monitor the temperatures and be as flexible as we can, but we also want to avoid causing potential ice jam flooding, which can occur when releases are too high amidst freezing temperatures,” Farhat said.

Runoff into the system above Sioux City, Iowa was 120 percent of normal with inflows of 1.3 million acre feet during the month of November. Normal inflows during the month of November usually total about 1.05 MAF. The Corps evacuated 1.5 MAF of stored floodwater last month.

On Nov. 29, the mountain snowpack is the Missouri Riber basin was 87 percent of normal in the reach above Fort Peck and 103 percent of normal in the reach between Fort Peck and Garrison dams, which consists primarily of the Yellowstone River basin. On average, 25 percent of the peak snowpack accumulation has occurred by Dec. 1.

View mountain snowpack graphic here: http://www.nwd-mr.usace.army.mil/rcc/reports/snow.pdf

Delay of Final Draft of AOP

The public comment period for the final draft of the Annual Operating Plan closed Nov. 25. The Corps is in the processing of reviewing written and emailed comments and those receive received and incorporating them into the report to the extent feasible.

In early October, the Corps commissioned a panel of four experts in hydrology and reservoir system operations to review, analyze and assess the operation of the six mainstem dams along the Missouri River leading up to, and during the Flood of 2011. The panel expects to complete and release its report Dec. 20.

“We have decided to delay the release of the Final Annual Operating Plan in order to allow us enough time to review the recommendations that come out of that report and possibly incorporate any feasible changes into our 2012 operations,” Farhat said.

The Corps expects to release the Final Annual Operating Plan the first week of January 2012 rather than in late December.

Biweekly conference calls planned for January

The Corps will communicate more frequently and more broadly as the 2012 season unfolds. In January, the Corps will begin twice monthly conference calls. During those calls, the dialogue will continue with federal, state, county and local officials, Tribes, emergency management officials, independent experts and the media to discuss conditions on the ground and current Corps’ reservoir release plans and forecasts.

Audio files of the conference calls will be made widely available. The official schedule for the January calls will be released later this month.

Reservoir Forecasts

Gavins Point releases are scheduled to remain at the current release rate of 40,000 cfs through Dec. 7. They are scheduled to be stepped down to the winter release rate of 20,000 cfs beginning Dec. 8. Average releases for the month of November were 40,100 cfs. The reservoir’s current elevation level is 1207 feet mean sea level.

Fort Randall releases are currently 39,000 cfs. Releases are expected to be stepped down in concert with the Gavins Point releases during December. The reservoir ended the month at elevation 1339. It will decline to approximately 1337.5 over the next week, then begin to refill ending the month near 1339. Fort Randall reservoir is drawn down each fall to make room for increased releases at the upstream dams for winter hydropower generation.

Big Bend releases are expected to average 25,000 cfs during December. Average releases for the month of November were 34.2,000 cfs. The reservoir will remain near its normal elevation of 1420 during the month.

Oahe releases are currently 33,000 cfs. Average releases for the month of November were 36,300 cfs. The reservoir ended the month near elevation 1607.1 feet, dropping by 1.9 feet from the previous month. It is expected to end the month of December near elevation 1605.9, down another 1.2 feet. the base of the annual flood control pool at Oahe is 1607.5 feet.

Garrison releases are currently 28,500 cfs and will begin to be stepped down this weekend. Average releases for the month of November were 28,400 cfs. The reservoir ended November at elevation 1839.8 feet, down 2.1 feet from its October end of month level. The reservoir is forecast to end this month at elevation 1839.2, down 0.6 feet from where it currently sits. The base of the annual flood control pool at Garrison is 1837.5 feet.

Fort Peck releases are currently 10,000 cfs, which is what the releases out of the reservoir averaged during the month of November. The reservoir ended the month at elevation 2237.1, down 0.6 feet from the previous month. It is expected to drop by 1 foot this month. The base of the annual flood control pool at Fort Peck is 2234.0 feet

The reservoir releases and elevations discussed above should not be assumed to be definitive. Additional heavy precipitation into the basin could cause adjustments to the reservoir release rates.

The six mainstem power plants generated 997 million kilowatt hours (kWh) of electricity in November. By the end of the calendar year, power production is projected to reach 11.1 billion kilowatt hours. The long-term average is approximately 10 billion kilowatt hours.

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To view the detailed three week release forecast for the mainstem dams, go to: http://www.nwd-mr.usace.army.mil/rcc/reports/twout.html.

MISSOURI RIVER MAIN STEM RESERVOIR DATA
Pool Elevation
(ft msl)
Water in Storage – 1,000 acre-feet
On November 30
Change in November
On November 30
% of 1967-2010 Average
Change in November
Fort Peck
2237.1
-0.6
15,587
108
-131
Garrison
1839.8
-2.1
18,833
107
-622
Oahe
1607.1
-1.9
18,712
112
-539
Big Bend
1420.7
+0.3
1,660
97
+11
Fort Randall
1339.0
-2.9
2,384
101
-175
Gavins Point
1207.0
-0.3
367
87
-8
57,412
108
-1,464

WATER RELEASES AND ENERGY GENERATION FOR NOVEMBER
Average Release in 1,000 cfs
Releases in 1,000 af
Generation in 1,000 MWh
Fort Peck
10.1
599
100
Garrison
28.4
1,692
263
Oahe
36.3
2,163
298
Big Bend
34.2
2,035
125
Fort Randall
38.8
2,308
131
Gavins Point
40.1
2,388
80
997