The risk levels displayed on the map are based on spring run-off potential. Other factors can alter that flood risk level. (CBC)

Officials worked feverishly Friday to stay on top of some of the worst flood conditions that parts of the Prairies have seen in more than 150 years.

Rising waters have already forced more than 700 people in Manitoba to head to higher ground. Although sandbagging efforts have spared many homes and communities so far, the province's emergency measures minister is urging Manitobans to remain vigilant.

Some 80 highways and hundreds of municipal roads are washed out, while 15 communities primarily in the province's south have declared states of emergency, Steve Ashton said.

Officials warn that the crest of the flood is still weeks away, and worse still is the feeling that both the Red and Assiniboine rivers are on track to crest at the same time. Experts think the Red River's water level will be the higher than it was in 2009, which was the second-highest water level on the Red since 1852. It was only eclipsed by the devastating 1997 floods.

Most of those evacuated have hailed from the Peguis, Roseau River and Dauphin River First Nations. But overland flooding has also threatened St. Laurent, Headingley, St. Francois Xavier and elsewhere along the Assiniboine.

Soil levels are highly saturated heading into spring, and heavy snowpack is adding to the flood and contributing to ice jams in some places, CBC News meteorologist Johanna Wagstaffe said.

Manitoba officials on Friday afternoon said an ice jam on the Assiniboine River near Holland, had broken up and would result in a temporary rush of water into Winnipeg.

"The flow surge will cause a rise in the Red and Assiniboine rivers in Winnipeg of between one and 1½ feet on Saturday," officials noted in a bulletin.

The city said no additional sandbagging would be needed as properties along Winnipeg's rivers have protection in place to meet the surge.

Saskatchewan communities declare emergencies

In neighbouring Saskatchewan, water flows are up significantly along the Qu'Appelle River 150 kilometres east of Regina.

Six communities have declared local states of emergency, including the hard-hit Cowessess First Nation. The province has set up a task force to ensure reserves have the equipment they need to fight the floods.

The situation in Saskatchewan was somewhat improved on Friday, as cooler temperatures slowed the flow of water from new snowmelt. That lull gave communities a chance to reinforce their sandbagging efforts. But a sharp spike in temperatures could cause serious problems.

Flooding also raises fears that well water could become contaminated with E. coli and other substances.

A strange taste or colour, or water pooling around wellheads could be a sign that a well has been contaminated, Terry Hanley of the Saskatchewan Watershed Authority warns.

"You can't always tell. It's not like the water turns black … so the only way you can truly determine is by testing," he said.

The Winnipeg owner of this car left it sitting on blocks to keep it away from rising water levels on Sunday. (Trevor Hagan/Winnipeg Free Press/Canadian Press)

More than 100,000 people could be affected, Hanley said. The Watershed Authority is offering free testing to people who think their water may be contaminated.

The picture was looking slightly better in southern Alberta on Friday, as a dump of new snow in Medicine Hat never materialized. Between 10 and 30 centimetres of fresh snow fell across southern Alberta on Thursday, but Medicine Hat was largely spared.

Relieved city officials said the threat is diminishing, but local residents are still plugging sewers and homes near the Seven Persons Dam with sandbags. Another light dusting of snow is possible on Monday.

"We're worried about a couple of feet now, as opposed to a couple of metres of water," city spokeswoman Brandy Calvert told CBC News.

Though cautiously optimistic, city officials say the state of emergency for the city remains in place.