Corps prepared to handle potentially high runoff season

With the spring runoff season just a month away, the U.S. Army Corps of Engineers Missouri River Basin Water Management office is prepared to handle another potentially wet year. 

Total storage in the Corps� six mainstem reservoirs currently sits at 56.9 million acre feet, down 9 million acre-feet from the crest last July, and just 100,000 acre-feet above the base of the annual flood control pool.

�We are currently monitoring snow conditions on the plains, which are similar to the above-normal conditions we saw in both 2009 and 2010,� said Jody Farhat, Chief of the Water Management Division.  �Mountain snowpack is running ahead of last year, but the big unknown is the rainfall.�  Last year�s high runoff in the Missouri River basin and resulting flooding was due in large part to widespread heavy rains. 

According to Farhat, it�s still too early to know whether basin states can expect flooding this spring. �Although there is a considerable amount of snow out there and soil conditions are moist in many areas, there are many other factors that influence flood potential.  These include how quickly the snow melts, whether or not it is accompanied by rain, and whether ice jams will contribute to flooding during the melt,� she said.  Throughout the year the Water Management office adjusts releases at each of the dams to reduce the potential for flood damages to the extent possible.

Mountain snowpack is 112 percent of normal for this time of year above Fort Peck, and 111 percent between Fort Peck and Garrison (the Yellowstone River basin). Traditionally, 61 percent of the peak accumulation of mountain snow has occurred by Feb. 1.

Runoff for 2011 is forecast to total 28.4 MAF, 114 percent of normal. The 2010 total was 38.8 MAF, 156 percent of normal.

Releases from Gavins Point Dam averaged 18,500 cubic feet per second during January. The long-term average for January is 17,200 cfs.  Releases were increased from 19,000 to 21,000 cfs in early February and are expected to remain at that level through mid-March, but may be adjusted if necessary in order to avoid ice jams or downstream flooding.

Fort Randall reservoir rose 5.3 feet last month as it received hydropower releases from Oahe and Big Bend. The reservoir ended January near elevation 1345.8 feet. It is expected to climb 4.2 feet in February, ending the month near elevation 1350, the base of its flood control zone.

Big Bend reservoir will remain in its normal range of 1420 to 1421 feet. Releases will be adjusted to meet hydropower needs.

Oahe reservoir releases averaged 22,500 cfs during the month of January. They are expected to average 22,300 cfs during the month of February. The reservoir rose 0.1 foot in January, ending the month essentially level at 1605.4 feet. It is expected to climb slightly by 0.8 foot in February, ending the month near elevation 1606.2, which 1.3 feet below the base of the annual flood control zone.

 Garrison Reservoir fell by 1.7 feet in January, ending the month at elevation 1840 feet.  Releases were gradually increased from 21,000 cfs to 25,500 cfs during the month, and then to 26,000 cfs in early February.  Releases will remain near that rate during February if river conditions permit.  The reservoir will decline about 1.7 feet this month, and is expected to end the month near elevation 1838.3, which is 0.8 foot above the base of the annual flood control zone

Fort Peck reservoir maintained an average of 8,900 cfs during the month of January.  Releases were increased from 9,000 to 10,000 cfs at the beginning of February.  They will be held at that rate through the end of the month.  The reservoir dropped by 0.1 foot in January, ending the month near elevation 2235.3 feet. It is expected to drop about half a foot in February, ending the month near elevation 2234.8, which is 0.8 foot above the base of the annual flood control zone.

The six main stem power plants generated 745 million kilowatt hours of electricity in January, 103 percent of normal.  Total energy production for 2011 is forecast to reach 10.4 billion kWh. The long-term average is approximately 10 billion kWh.

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