Frigid temperatures, plenty of demand — so why is Winnipeg's river skating trail at risk?

Winter usually means a skate, walk or run on the river for thousands of Winnipeggers.

The denizens of this city have learned to embrace sub-zero temperatures by strapping on their skates for a sprint on the frozen Red or Assiniboine rivers.

But this favourite pastime may not be an option for the first winter in nearly 20 years — despite the weather being cold enough, and the tens of thousands waiting to once again stroll, skate, run or maybe even bike down the frozen rivers.

So what gives? 

It has a lot to do with an unusual fall flood, followed by dropping water levels and unstable ice. 

Conditions this winter are unprecedented, says Jay Doering, a civil engineering professor at the University of Manitoba and a flooding expert.

Ice bound to break

An unusually wet fall saturated the ground and brought the Red River to a level higher than any fall on record.

The water level on the Red reached as high as 17.3 feet at James Avenue on Oct. 23. It's fallen dramatically since then — to under seven feet James, as of Friday — but that's still well above the normal ice level of around zero feet James.

The river began freezing, though, at an unusually high level. That ice has frozen into chunks, says CBC meteorologist John Sauder.

"It's almost like broken glass sitting on top of the river," he said.

As the river level has dropped, a gap has formed between those solid blocks of surface ice and the water — air pockets that cannot last.

"The ice sheet is clearly going to have to adjust," Doering said. "It's going to have to break, it's going to have to crack, and I don't know where those cracks are going to appear."

Normally, the water stays at a steady level through the winter. This year, the water level is likely to continue dropping, he says — probably until March.

"How that ice sheet adjusts to that drop? It's not something I'm comfortable predicting," he said.

He also expects the riverbank ice to break, with the river narrowing as it drains.

"I don't know, or can't say, that it's going to break off cleanly, so I have concerns about where fissures might open up and what might happen as the ice sheet attempts to crack and refreeze."

He stresses, though, that the decision on whether or not to open a river trail isn't his.

That call will rest with staff at The Forks, who are monitoring the river every day to ensure safety.

The loss of the skating trail would be a significant blow to The Forks — 800,000 people used the icy trail last year, according to officials.

Flowing fast

Another complication for the trail this year is the speed at which the water is flowing. 

The more water you have in a constrained space, the faster it moves, says Nora Casson, a Canada Research Chair in Environmental Influences on Water Quality.

Because of the speed at which the Red River has been flowing, it's been difficult for the water to freeze this year.

"The river is kind of like a pipe, right? It's fixed in size," said Casson, also a geography professor at the University of Winnipeg. "If you are trying to force more water through the same shape, it'll move more quickly."

The outlook for freezing has been even further complicated by fluctuating temperatures, which have swung from above to below freezing like a pendulum, she says.

In spite of all the uncertainty, The Forks isn't giving up on the river trail.

Every year is different. Last year, the trail stretched 8.6 kilometres long and operated for a record-breaking 75 days. By contrast, it was open for just 33 days in 2016-17. 

"Ultimately, we're always at Mother Nature's whim when it comes to building the river trail," said Larissa Peck, manager of marketing and communications at The Forks.

If the trail doesn't open at all, it would be the first time that's happened since 2000. But Peck says it's premature to sound the death knell for this season.

"We still feel we have a few weeks before we can make that call."

Last season, the skating rink on the Assiniboine at The Forks dock opened on Dec. 28, but the first section of the trail didn't officially open until Jan. 4. That was on par with previous years, Forks officials said at that point.

Peck says The Forks is speaking with the organizers of various winter events on the river, like the outdoor curling bonspiel, to ensure those events can go ahead even without a river trail. 

If need be, the popular warming huts would pop up elsewhere, and The Forks would expand its on-land skating options. 

Casson said climate change shouldn't necessarily be blamed for individual weather events, but the trend of intense storms — such as a freak Thanksgiving storm that pummelled trees and power lines — and winters that are less consistently cold isn't going away. 

"When we think about the types of recreational activities that we enjoy during winter, like skating at The Forks, those things are not looking good for the future."