About 11,000 Minot residents are being ordered to leave their homes even earlier than expected this week as the Souris River gets closer to swamping the North Dakota city with the worst flooding in four decades, officials said Tuesday.

Mayor Curt Zimbelman said about a quarter of the city's residents were being told to evacuate by 6 p.m. Wednesday, and officials plan to sound the warning sirens if water spills over Minot's protective levees before that looming deadline. Authorities had previously encouraged people to be gone later that night.

"Public safety is paramount," Zimbelman said during an afternoon news conference. "The water is rising fast, and people need to get evacuated as soon as possible."

The Souris River that loops down from Canada through north central North Dakota is bloated by heavy spring snowmelt and rain on both sides of the border.

Water is expected to reach the top of city's levees within the next two days and the resulting flooding is expected to dwarf the historic flood of 1969, when the Souris River reached 1,554.5 feet above sea level.

Zimbelman said the river at the city's Broadway Bridge was just a tenth of an inch shy of that level Tuesday afternoon, and it's expected to hit nearly 1,563 feet this weekend.

The 1969 flood prompted the Army Corps of Engineers to build a dike system that has been beefed up several times this spring.

But those levees are unable to handle flows from Saskatchawan of approximately 28,000 cubic feet per second.

The corps will mitigate those high flows through its management of the Lake Darling reservoir, said Deputy Commander Lt. Col. Kendall Bergmann.

The corps on Tuesday cut the outflow from Lake Darling to 8,000 cubic feet per second after nearly two inches of rain fell on Ward County's Des Lacs River, Plans call for upping the outflows in 1,000 cfs increments starting Wednesday morning, up to 15,000 cfs by Thursday.

Bergmann said the corps got approval from Congress to take Lake Darling 2½ feet lower and to go 5 inches above management pool level.

"So by increasing the flows over the next few days, we're almost going to empty Lake Darling," he said. "So when 28,000 cfs comes in, the lake can handle it and I'm only going to release about 20,000, max. So that water will be retained in Lake Darling, and less amounts will be sent through the remaining Souris basin."

Zimbelman said officials in Minot are focusing efforts on building dikes to protect critical infrastructure such as the sewer system, water plants, schools and City Hall. The city also is working on plans to put up secondary dikes outside fringe areas.

"Once we have the critical sites secured, we'll start on these other areas trying to protect as many homes and businesses as possible," he said. "We will continue until the water pushes us out of the area."

Officials at Minot International Airport, which sits on a hill on the north part of town, issued a statement Tuesday saying the airport will remain fully operational.

Similar efforts are being made to protect infrastructure in the nearby town of Burlington, where about 1,200 people live.

Gov. Jack Dalrymple said Tuesday afternoon that residents in Burlington evacuation zones need to be out by noon Wednesday. Ward County residents living along the river must evacuate by 6 p.m., he said.

About 10,000 Minot residents were evacuated earlier this month before the river hit 1,554.1 feet. They were later let back into their homes, but were cautioned to be ready to leave again quickly.

North Dakota National Guard commander Dave Sprynczynatyk said the latest evacuation order affects about 11,000 people in 4,200 homes.

Nearly 500 Guard soldiers were to be in Minot by the end of the day Tuesday, providing traffic control, making sure people had left their homes and securing neighborhoods. The Guard also has increased monitoring of the city's levees to every 30 minutes.

Sprynczynatyk said the impending flood will probably be one of greatest as far as the impact to the community as a whole that he's seen during a 40-year career.

"What I see right now is probably the most devastating in terms of the number of people directly impacted and what will likely be the damage to homes as the water begins to overtop the levees and fill in behind," he said.

Ann Hoggarth, who lives right next to the river, told The Associated Press that she feels numb and very emotional. She is struggling to move some of her belongings to higher ground.

"I've got three stories so I'm hoping the furniture will be OK upstairs, but I'm a single mom and I had to ship my kids off to their dad, so I don't have anyone to help me," she said.

The high water is expected to begin hitting Minot by about Thursday, with the river jumping more than seven feet by Saturday. The historical record of 1,558 feet set in 1881 is forecast to be topped on Friday or Saturday.