"Unprecedented" Summer-long Missouri River Flood
June 8, 2011 • 2:03PM

"Unusual" weather conditions have created an "unprecedented" water runoff that could cause the Missouri River basin floods to continue through mid-August, the U.S. National Weather Service warned yesterday. Record snowfall in the Rocky Mountains this past winter, is now melting, which, combined with unusually heavy rains, could keep the river in flood for many weeks, the Alaska Dispatch reported today.

"We do have quite an unusual set of circumstances, meteorologically," Lynn Maximuk, central region director of the National Weather Service, said yesterday. "There are some extremely high water levels that will persist for quite a period of time. The rises along the Missouri have been caused by really a year's worth of rainfall across the basin over the last two weeks. In addition, snowfall in the mountains is at about 140% of normal."

The Army Corps of Engineers is projecting that the snowmelt and rains will create a total runoff of some 55 million acre-feet of water, the highest runoff level since records were first kept in 1898! Reservoirs are already overflowing, and the snow will continue to melt until August. More rainstorms are expected from Montana and North Dakota to Nebraska in the coming days, which will exacerbate the flooding, Maximuk said. May was the second-wettest month for northern Wyoming, Montana, and North Dakota since 1889.

Water levels at the six dams in the river (on the Upper Missouri) are at record levels, and water will be released at every dam in succession, according to Corps Missouri Basin reservoir official Kevin Grode. "We are going to be testing the system, because we'll be releasing more water than has ever been released before. The dams are safe, but the levee system is more vulnerable and could be stressed throughout the year," Grode said. "We've filled up all the reservoirs we intended to use to handle the runoff snowpack from the mountains," Grode said. "The mountain snowpack still exists, and it's ready to come off in the next several months."