Breakup fails to rise to occasion
River water levels peak at and below average
Roxanna Thompson
Northern News Services
Published Thursday, May 15, 2014
DEH CHO
Breakup brought little excitement to the Deh Cho this year and came with average to below-average water levels.
The ice on the Mackenzie River at Fort Simpson was still holding on May 7 at 2 p.m., but by the following day it was flowing freely in the centre of the river. - Roxanna Thompson/NNSL photo
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The series of breakups began in Fort Liard May 3.
The ice on the Liard River broke and then jammed overnight, but was flowing again the following day.
"It's pretty slushy ice," said Chief Harry Deneron of Acho Dene Koe First Nation.
The water level only rose a small amount on the river and didn't cause any flooding in the hamlet, he said.
The Liard River peaked at 9.20 metres during breakup, which is only slightly below its average of 9.22 metres, said Roger Pilling, a hydrometrics supervisor with Water Survey of Canada based in Fort Simpson.
The highest recorded peak was at 12.69 metres on May 1, 1989.
The water level at Fort Liard on the Liard River is usually an indicator of what Fort Simpson can expect, said Pilling.
The water level at the hamlet is expected to rise again in June because of above normal snowfall in south eastern Yukon at the river's headwaters.
At least normal levels, which are approximately eight metres, are expected, he said.
The Liard River at Nahanni Butte broke a few days later, mid-week.
The water levels didn't pose any problems, but the ice is hindering community members, said Frank Moretti, band manager for the Nahanni Butte Dene Band.
The river pushed up and left behind approximately 18 metres of ice on both sides of the river, as high as three metres in some places.
"Call them small icebergs if you want," said Moretti.
The accumulated ice means that residents won't be able to put their boats in the river for at least a week, he said. Last year the ice was swept away within two days of breakup.
The Liard River began breaking up at the ferry landing outside of Fort Simpson May 5.
By the next morning it was approaching 4 Mile, one of the village's subdivisions.
The Mackenzie River in front of Fort Simpson peaked May 8 at 11.165 metres, slightly below the average of 11.4 metres, said Pilling.
The maximum peak for the river in that location was approximately 15.5 metres in 1963, the year of the village's substantial flood. Many people remember the more recent flood of 1989 when the river peaked at 14.95 metres, he said.
"It varies a lot," said Pilling.
The lowest recorded water peak during breakup around Fort Simpson was 7.36 metres in 2000.
"Thankfully another lacklustre breakup. That's the way we like it," said Mayor Sean Whelly.
Whelly missed breakup because he was attending the Northwest Territories Association of Communities' annual general meeting in Inuvik.
He followed the progress through photos and updates residents posted to Facebook.
Changes over time
Whelly has noticed a definite change in the annual spring breakup over the approximately 32 years he's lived in the village.
"It's no where near the way it used to be," he said.
In his first 15 years, Whelly said break-up was a major event every year with the confluence of the Mackenzie and Liard Rivers creating piles of ice in the middle of the river that were so large they would mask helicopters when they flew behind them. Flood waters also used to encroach on the lower lying parts of the island annually.
"You just don't see that anymore," he said.
"The ice is thinner."
The numbers support Whelly's observations. There used to be an average ice thickness of 1.25 metres at the mouth of the Liard River, said Pilling.
The ice, on average, has been less than one metre thick in the last five years, although this year it reached that mark.
The Mackenzie River at Fort Simpson used to measure an average of 1.1 metres thick.
This year it reached one metre at peak thickness in mid-April, but in the past few years it has been between 80 to 90 cm, said Pilling.
Pilling couldn't give any reasons for why the ice is thinner on average.
The date of the breakup also plays a role in how easily the ice breaks. UV light weakens the ice and makes it softer.
If it breaks later, the ice is weaker, said Pilling.
Whelly said he doesn't miss the big, dramatic breakups.
"We're better off without that," he said.
