By Kevin Murphy
KANSAS CITY, Mo (Reuters) - Flooding will force the evacuation of one-quarter of North Dakota's fourth largest city and levee breaches forced 300 residents from a Missouri town as flooding worsened on Tuesday, officials said.
About 12,000 residents of Minot have been ordered to leave their homes by 6 p.m. Wednesday local time -- four hours earlier than originally planned -- as heavy water releases from reservoirs along the Souris River threaten to overwhelm barriers, officials said.
Heavy rains across the Souris River basin over the last six weeks have forced Canada reservoirs to release water at unprecedented rates. In turn, the Lake Darling Dam above Minot will have to release water at rates beyond current protection.
Rain has worsened the flooding and forced Minot Mayor Curt Zimbelman to speed up the evacuation, he told reporters. Residents in threatened areas just outside Minot also were under mandatory evacuation.
"We have been riding a pretty thin edge and regrettably, the storms over the last several days have really pushed the Souris River basin into territory that we have never seen before," said Allen Schlag, a hydrologist at the National Weather Service's office in Bismarck, North Dakota.
Schlag said the water releases from Lake Darling should be expected to cause two weeks of inundation in Minot as flows are ramped up to peak levels by late June and held there for several days before a gradual pullback into July.
"It's tough to imagine that when this is all shaken out and done that there will be any records that don't have 2011 stamped on them," Schlag said of the Souris River flooding.
Amtrak suspended Empire Builder service Tuesday in part of Minnesota, North Dakota and eastern Montana due to flooding.
Flooding along the Missouri River continued to take its toll on levees in northwest Missouri.
The 300 Craig, Missouri, residents were ordered to evacuate after two levees south and west of town on the Missouri River were breached and recently fortified earthen and sandbag barriers around the town were expected to be overwhelmed by water, Holt County Commissioner Bill Gordon said on Tuesday.
"Water is headed this way," Gordon said. "People are pretty stressed out."
In recent days breaches have inundated some farmland and homes, particularly around the village of Big Lake, Missouri.
Levees have also failed in Atchison County north of Holt County. Both counties have reported voluntary evacuations as well as the closing of numerous roads and Big Lake State Park.
Heavy rains added to woes across the Missouri River basin from Montana through Missouri Tuesday, swelling the river and its tributaries, pressuring levees and flooded areas, and forcing evacuations and road and rail closings.
The rains also forced the U.S. Army Corps of Engineers to change its water release plans from some of its six dams in Montana through South Dakota. It has released record amounts of water from the dams to relieve pressure from snow melt and heavy rains.
The Corps said Tuesday it would increase releases from Gavins Point Dam on the South Dakota-Nebraska border to 160,000 cubic feet per second from 150,000 in two stages starting on Wednesday and holding that peak starting Thursday.
The Missouri River runs freely from Gavins Point for more than 800 miles to the Mississippi River near St. Louis, making the releases from the dam a focus for downstream residents.
Peak releases are planned until at least mid-August from the dams and high flows are expected until December.
Flooding and heavier water flows have forced the closure of bridge crossings of the Missouri River from just south of Omaha for more than 100 miles south. More bridges and railroad lines may have to close as flooding continues.
North of Omaha, the Fort Calhoun nuclear power station remains shut due to Missouri River flooding, but protected by temporary flood barriers and dry, said Mike Jones a spokesman for the Omaha Public Power District.
Two coal-burning power plants along the river are operating and also protected by flood barriers, Jones said.
The Cooper nuclear power station near Brownville, Nebraska, is operating and protected by flood barriers, said Mark Becker, a Nebraska Public Power District spokesman.
(Additional reporting by David Bailey in Minneapolis; Editing by Greg McCune)