MINNEAPOLIS, June 3 (Reuters) - Hundreds of people in North Dakota and South Dakota evacuated affluent areas along the swollen Missouri River on Friday as federal officials stepped up water releases to relieve pressure on six reservoirs.
Heavy rains coupled with a deep melting snowpack have swelled Missouri River reservoirs from Montana through South Dakota to near capacity. Residents in Nebraska, Iowa and Missouri also were braced for widespread flooding.
“The Missouri River will be high for the rest of the summer,” said John Grothaus, chief of planning in the U.S. Army Corps of Engineers’ Kansas City district.
About 400 people from upscale neighborhoods in Bismarck, North Dakota’s capital, were evacuating and South Dakota Governor Dennis Daugaard urged residents of the “country club” area of Dakota Dunes to leave by midnight.
Workers in Bismarck were finishing a series of levees on Friday as federal water managers ramped up spills upstream from Garrison Dam, officials said.
The Army Corps of Engineers increased the flow through the Oahe Dam above Pierre, South Dakota’s capital, on Friday. The river level is expected to rise about four feet (1.2 metres) as releases accelerate to maximum planned levels by Tuesday.
Flows from most Missouri River reservoirs already were at record levels on Friday and the accelerated releases will add several feet to the high river levels deep into July.
The maximum planned release rates are expected to push the Missouri River up to seven feet (2.1 metres) above flood stage at Sioux City, Omaha and Kansas City.
The governors of Missouri, Iowa and Nebraska have been surveying areas already flooding along the Missouri River.
Officials stopped short of mandatory evacuations in South Dakota. Police and National Guard members will go door-to-door in Dakota Dunes to warn residents who stay that the risks will rise with the water, utilities will be cut off eventually and they may not be able to leave later.
In Montana, the Corps increased water flows from Fort Peck Dam, while widespread flooding of Missouri tributaries has forced hundreds of evacuations and inundated smaller cities.
“We’ve had floods in the past, we’ve had disasters in the past, but we’ve never had anything that spreads from border to border like this,” said Monique Lay, spokeswoman for Montana Disaster and Emergency Services.
The Missouri River basin forms the northwest section of the Mississippi River system that stretches from the Rockies to western New York and funnels water down through Louisiana to the Gulf of Mexico.
The Corps held water in the Missouri reservoirs to reduce the impact from record Mississippi River flooding earlier this year. (Additional reporting by Laura Zuckerman in Salmon, Idaho, and Kevin Murphy in Kansas City; Editing by Jerry Norton and John O‘Callaghan)