Another major storm is tracking toward Manitoba, and the provincial government expects it will push its flood-fighting capacity to the limit.

The storm, expected to arrive Sunday or Monday, comes on top of four downpours in the last five weeks and the ground remains saturated. 

"It's impossible to exaggerate the seriousness of the situation," Steve Ashton, Manitoba's minister of emergency measures, told reporters on Thursday. "I'd say we're on a high state of alert again. Our flood defences will clearly be pushed to the limit. We are putting in place various initiatives to deal with that."

Work has resumed to shore up the Portage Diversion  and the Assiniboine River dikes, Ashton said.

'Our flood defences will clearly be pushed to the limit.' — Steve Ashton, minister of emergency measures

A flood bulletin released Thursday by the province stated "a forecast fifth major rain storm is raising serious flood concerns and will be closely monitored over the next four days.

"Four major storms have already fallen on saturated soils affected by heavy flooding in the Assiniboine and Souris river watersheds. The cumulative effects of the flood and sustained storms are pushing the capacity of Manitoba’s flood-protection systems to or beyond their design capacity."

The flood on the Assiniboine River at Portage la Prairie is now considered to be a one-in-350-year event, the province stated.

A lot of water is also coming from Saskatchewan, which has seen far more than its usual share of rain so far this year, CBC meteorologist Michelle Leslie reported. Estevan, for example, has seen 224 millimetres of rain in the past five weeks, she said. The town's annual average is 333 mm.

In Manitoba, the Souris River basin has received almost 300 per cent of normal precipitation and areas of the Assiniboine River basin have received between 150 and 250 per cent of normal, according to the provincial government.

The predicted storm could push the Assiniboine River back up to the record levels it reached a few weeks ago.

As a result of the high flows on the Portage Diversion channel, evacuation alerts will be reissued by the Rural Municipality of Portage la Prairie to 45 homes near the channel.

The new storm will also add to the challenges the province already faces, Ashton said: "When you look at the historic scale of this flood, it is very clear that we are going to be dealing with this for many days and weeks and months to come."

The Assiniboine crested several weeks ago, but not before troops worked tirelessly to reinforce dikes and build up the Portage Diversion to handle higher flows and send the water to Lake Manitoba, which is now a major threat to homeowners along its shores.

Numerous properties along the lake — Twin Lakes Beach, Laurentian Beach, Sandpiper Beach, Pioneer Resort, Delta Beach, and Johnson Beach — have been heavily damaged in the past two weeks.

Powerful winds whipped across swollen lake creating large waves that pounded the shore and washed inland.

Dike deliberately cut

When the Assiniboine was rising several weeks ago, the province decided to deliberately cut into a dike and intentionally flood farmland near Portage la Prairie. The intentional flood was intended to prevent a much larger natural flood downstream.

The controlled release prompted frantic sandbagging because it was expected to surround about 150 homes and flood more than 200 square kilometres. However, fewer than 3.5 square kilometres were affected before the dike was sealed a week later when river levels began to recede.

The flood fight has since shifted to Lake Manitoba, where hundreds of residents and cottagers have been ordered to leave their properties due to high winds and high waves. 

Storms that have battered the area have caused extensive damage, downed hydro lines and washed out roads. Lake Manitoba isn't expected to crest until mid-July and is anticipated to remain high well into the winter.

With files from The Canadian Press