Montana Snowpack Similar To 2011 When Missouri River Flooded

Mar 28, 2018

Credit USDA

Observers say snowpack levels in the Northern Rockies are like those in 2011. That snowmelt in part brought historic flooding along the Missouri River basin through South Dakota.

However, those with the National Weather Service aren’t raising the alarm just yet.

Some snowpack levels in western Montana are anywhere from 120 to 130 percent above normal.

Those numbers are similar to levels in 2011, when the Missouri River flooded and displaced many people for weeks.

However, Mike Gillispie, the Senior Service Hydrologist for the National Weather Service in Sioux Falls, says that’s not a cause for concern, yet.

“Most of the issues we saw in the Missouri River were not caused solely by the snowpack,” Gillispie says. “Most of the eastern two-thirds of Montana and the western third of North Dakota in May, into early June, received basically a year’s worth of rain in about a two week period up there.”

Gillispie says eastern Montana and western North Dakota would have to receive about 15 inches of rain in the next two months, while the most of the snowmelt occurs. He says that’s unlikely.

That amount of rain is what caused issues on the Missouri River and pushing water through the reservoir system.

He says higher than normal river levels are expected this spring.

“But, the chances of seeing a repeat of 2011 is extremely rare," Gillispie says. "Even with the snowpack being where it is right now, and that area gets two or three inches above normal rainfall over the next couple of months, that amount of water should be able to easily be pushed through the reservoir system without causing any flood concerns.”

During flooding in 2011, reservoirs on the Missouri River were releasing 150,000 cubic feet of water per second.

Gillispie says normal flows out of Gavin’s Point dam near Yankton normal run about 30,000 to 40,000 thousand cubic feet per second. He says if the Army Corps of Engineers bumps that up to 50,000 or 60,000 cubic feet that shouldn’t cause any issue downstream.