The following is a rundown of the U.S. Army Corps of Engineers flood forecast for the upper portion of the Missouri River Basin. At this point, the Corps does not look for a big flood problem. -- Bryce
Omaha, Neb. — The 2014 runoff forecast in the Missouri River Basin above Sioux City, Iowa, has increased to 30.6 million acre feet (MAF), 121 percent of normal. Runoff of this magnitude is expected to occur on average once every four years. The average annual runoff is 25.2 MAF. Runoff during the month of February was 1.2 MAF, 112 percent of normal.
"Above normal mountain snowpack, high soil moisture conditions and deep frost depths were factored into our increased runoff forecast," said Jody Farhat, Chief of the U.S. Army Corps of Engineers Missouri River Basin Water Management Division. "Mountain snowpack has increased steadily during the last several weeks and colder than normal temperatures continued through February. Wet soil conditions and deeply frozen soils increase the potential for runoff when snow melts or spring rainfall occurs."
As of March 7, mountain snowpack was 127 percent of normal in the reach above Fort Peck and 135 percent of normal in the reach between Fort Peck and Garrison. "Mountain snowpack is at about the same level it was at this time in 2011, but still far below where it peaked in 2011. Light plains snowpack has accumulated in the eastern Dakotas and parts of Montana, but the remainder of the basin has little or no plains snowpack," said Farhat. Typically about 80 percent of the peak mountain snowpack accumulation has occurred by early March.
The total volume of water stored in the Missouri River Mainstem Reservoir System is currently 50.6 MAF, compared to 56.1 MAF at the base of the flood control zone. Reservoir storage is down due to the lingering effects of the 2012 drought. "The full 16.3 MAF flood control storage zone along with an additional 5.5 MAF of conservation storage is available to manage runoff from this year's snowpack and rainfall," said Farhat. The upper three reservoirs, Fort Peck in eastern Montana, Garrison in North Dakota, and Oahe in South Dakota, remain 5 to 11 feet below the desired operating levels.
"River ice may be an issue in some locations during the spring runoff season. 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.
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