Warmer weather has turned thoughts to melting snow, but observers say the snowpack that has accumulated so far this winter shouldn’t create major spring flooding in eastern South Dakota.
Snowpack along the James River valley is running up to 24 inches at Jamestown, N.D.; 30 inches at Huron and a bit over 25 inches at Yankton, said hydrologist Mike Gillispie of the National Weather Service in Sioux Falls.
“Around Jamestown, the snow depth is anywhere from 1 to 2 feet, mostly around 10 to 15 inches,” he said. “If all that snow melted in a day, that’s the equivalent of getting 2 to 3 inches of rain.”
Near Huron, the snowpack has the water equivalent of about a half-inch of rain, he said.
“There isn’t any worry about flooding on the James,” he said. “Most of the area along the James River has a 20 to 30 percent chance for major flooding.”
Gillispie said major flooding is not expected along the Vermillion River, either. “With the Vermillion River, there is a 50-50 chance of minor flooding in the Davis-Wakonda area. That’s pretty normal.”
The story is similar for the Missouri River, but things could change during the next two months.
The Missouri seems to be in good shape after years of low levels, said Paul Johnston, a U.S. Army Corps of Engineers spokesman in Omaha, Neb.
“If we continue to get normal precipitation for the next two to three months, there should not be any significant flood issues to deal with, unless it all falls in a single event,” he said.
“(Last year) was the first year since 1999 that we had normal runoff. The big reservoirs rose 10 to 14 feet,” Johnston said. “We are sitting better, but we’re still way down. Fort Peck (Mont.) was more than 30 feet below the normal level.”
Runoff in 2008 totaled 26.4 million acre feet. Normal is 24.8 MAF.
Larry Cieslik, chief of the corps’ water management office in Omaha said higher inflows and lower releases pushed reservoir storage to 44.8 MAF, he said.
The 2009 runoff forecast is 22.3 MAF because the mountain snowpack is near normal but the plains snowpack is below normal.
The agency monitors the snowpack in two Rocky Mountain basins. Johnston said the combined snowpack is 98 percent of normal, adding that he hopes the spring melt will continue the relief from years of drought.
“We are hoping that normal snowpack is going to give us a glimmer of hope for continued recovery,” he said. “But it’s early, and we are not making any prognostications.”
Gillispie said the forecast for February and March calls for near-normal temperatures and above-normal precipitation. Then it shifts to dry conditions for eastern South Dakota in April.
Johnston said a big contributor to increased reservoir storage last year was low releases due to high water in Iowa, Kansas and Missouri. “They had flows that were comparable and sometimes even higher than in 1993 when they had the high flood records.”
He said spring pulses are planned for Gavins Point Dam near Yankton in March and May, adding that seasonal releases will meet the needs of the endangered pallid sturgeon, least tern and piping plover.
Information from: Yankton Press and Dakotan,
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