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February runoff higher, but 2015 Missouri River forecast still slightly below normal

Published March 6, 2015
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, NE — The U.S. Army Corps of Engineers Missouri River Basin Water Management Division reports runoff in the Missouri River Basin above Sioux City, Iowa was 2 million acre feet (MAF) during February, 186 percent of normal. The increased runoff was caused by above normal temperatures in the upper Missouri Basin that limited river ice build-up, and melted both plains and low elevation mountain snows. However, the 2015 runoff forecast in the same reach is 24.6 MAF, 97 percent of normal, and the March runoff forecast is about 1 MAF less than in February.

“The reservoirs are designed to capture spring runoff that is stored and released during the summer and fall to provide water for navigation, hydropower, water supply for municipalities and power plants and other uses. Essentially, runoff that would normally arrive in the regions above Fort Peck and Garrison dams during March and April occurred early this year,” said Jody Farhat, chief of the Corps’ Missouri River Basin Water Management Division. 

The lower runoff forecasted in March is a result of slightly below normal mountain snowpack above Fort Peck and Garrison dams, drying soil moisture conditions and light plains snowpack. As of March 1, mountain snowpack was 88 percent of normal in the reach above Fort Peck Dam and 97 percent of normal in the reach between Fort Peck and Garrison dams. Typically about 80 percent of the peak mountain snowpack accumulation has occurred by early March.

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

The total volume of water stored in the Missouri River Mainstem Reservoir System is 57.1 MAF, occupying 1 MAF of the 16.3 MAF flood control zone. “The Corps will continue to monitor snowpack, rainfall-runoff and basin soil conditions to fine tune the regulation of the reservoir system based on the most up-to-date information,” said Farhat. 

Beginning in mid-March, releases from Gavins Point Dam will be increased approximately 3,000 cubic feet per second (cfs) per day until navigation target flows are reached. Based on the March 15 system storage check, full-service navigation flow support will be provided for the first half of the Missouri River navigation season. Full-service navigation flow support is generally sufficient to provide a 9-feet-deep by 300-feet-wide channel. Flow support for the second half of the navigation season and the season length will be determined based on the July 1 system storage check. The navigation season opening dates are as follows: 

  • March 23 – Sioux City, Iowa 
  • March 25 – Omaha, Neb. 
  • March 26 – Nebraska City, Neb. 
  • March 28 – Kansas City, Mo. 
  • April 1 – Mouth near St. Louis, Mo.
Reservoir Forecasts

During February, releases from Gavins Point Dam averaged 19,000 cfs. Releases were reduced to 17,000 cfs in early March and will remain at that rate until mid-March when they will be increased to provide flow support for the navigation season. The reservoir behind Gavins Point Dam ended February at elevation 1206.9 feet. The reservoir will be lowered to 1206 feet in March and remain at that level.

Fort Randall Dam releases averaged 16,300 cfs during February. Releases will be stepped up in mid-March corresponding with the start of navigation support and will be adjusted as necessary to maintain the desired elevation at Gavins Point Dam. The reservoir ended February at elevation 1349.7 feet, up 3.7 feet during the month. The pool is expected to reach elevation 1355 feet in early April. 

Big Bend Dam releases averaged 18,800 cfs in February. Releases are expected to average 22,300 cfs this month. The reservoir will remain near its normal elevation of 1420 feet during March. 

Releases from Oahe Dam averaged 20,100 cfs during the month of February. Releases are expected to average 21,900 cfs in March. The reservoir ended February at elevation 1608.2 feet, up 1 foot during the month. The reservoir is expected to rise 1 foot during the month of March. 

Garrison Dam releases averaged 23,100 cfs in February. Releases will be gradually stepped down from 23,000 cfs to 18,000 cfs by mid-March. Ice conditions in the Bismarck, N.D., area will be monitored closely during the thaw and additional adjustments to Garrison releases will be made, if conditions dictate. The reservoir ended the month at elevation 1838.8 feet, down 0.5 feet from the previous month. It is expected to rise 0.6 feet during March. 

Releases from Fort Peck Dam averaged 6,900 cfs in February. Releases will remain at 7,000 cfs during March. The reservoir ended February at elevation 2235.2 feet, up 1 foot from the previous month. It is forecast to rise 1.3 feet during the month. 

The forecast reservoir releases and elevations discussed above are not definitive. Additional precipitation, lack of precipitation or other unknown circumstances could cause adjustments to the reservoir release rates. 

The six mainstem power plants generated 637 million kilowatt hours (kWh) of electricity in February. Typical power generation for the month of February is 620 million kWh. The power plants are projected to generate 9.6 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 Feb. 28

Change in February

On Feb. 28

% of 1967–2014 Average

Change in February

Fort Peck

2235.2

+1.0

15,047

109

+211

Garrison

1838.8

-0.5

18,146

110

-158

Oahe

1608.2

+1.0

18,893

110

+322

Big Bend

1420.4

-0.4

1,653

96

-24

Fort Randall

1349.7

+3.7

2,978

88

+270

Gavins Point

1206.9

-1.2

347

94

-29

 

 

 Total

57,064

108

+592

 

WATER RELEASES AND ENERGY GENERATION FOR FEBRUARY

 

Average Release in 1,000 cfs

Releases in 1,000 acre-feet

Generation in Million kWh

Fort Peck

6.9

383

62

Garrison

23.1

1,282

200

Oahe

20.1

1,118

167

Big Bend

18.8

1,046

65

Fort Randall

16.3

904

93

Gavins Point

19.0

1,056

50

 

 

Total

637



Contact
Serena Baker, U.S. Army Corps of Engineers, Northwestern Division
503-808-3710
serena.baker@usace.army.mil

Release no. 20150306-001