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Dehcho
Environment
South Slave

High water and snow levels elevate the NWT’s flood risk


There’s a significant risk of flooding this spring as high water and snow levels persist across much of the Northwest Territories, the territorial government said on Monday.

Releasing a study of the territory’s snowpack and water levels, the NWT government described concerning scenarios in most regions, the North Slave excepted.

The nine communities considered to be at risk are Hay River, Kátł’odeeche First Nation, Nahanni Butte, Fort Liard, Fort Simpson, Jean Marie River, Fort Good Hope, Tulita and Aklavik.

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How the flood season evolves will depend primarily on ice jams as river ice breaks up, a phenomenon that can be difficult to accurately predict.

A GNWT map of snow water equivalent in spring 2022. Blue is more, orange is less. Snow water equivalent measures how much snow is on the ground and how much water will be released into the environment when that snow melts.

Even before that jeopardy arrives, the GNWT said current snowpack and water levels present an obvious risk to communities where flooding is a recognized threat.

In general, the territory’s report stated, “winter temperatures across the NWT were colder than normal, which has led to a thicker ice cover than usual,” and residents in flood-prone communities should “prepare for potential flooding.”

Hay River and KFN

In the Hay River basin, the GNWT said, water levels are “at or near the highest levels ever recorded in Hay River at this time of year.”

Those levels are expected to remain high until at least the early summer, the territory said, and the ground is already heavily saturated, “which means most water will flow directly into rivers, creeks, lakes, and streams – which will likely increase the already high water levels.”

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Snow levels in the region are “very high” at 32 percent above the territory’s normal level.

“The weather experienced in the Hay River basin will have a large impact on the flood risk at break-up,” the territory’s report stated.

Dehcho

Fort Simpson and Jean Marie River experienced some of the most devastating NWT flooding last spring.

This time around, the GNWT said the Liard River – which affects Fort Liard, Nahanni Butte and Fort Simpson – has “extremely high snowpack” up to 76 percent higher than normal. That follows unusually high snowfall across the Dehcho this past winter.

“There is potential for ice jam flooding in the region,” the territory stated.

The Mackenzie River, meanwhile, was said by the territory to have “higher-than-average water levels and water flow.”

Beaufort Delta, Sahtu

“Throughout the Dehcho, Sahtu and Beaufort Delta, there is the potential for ice jam flooding,” the territorial government stated.

The territory said higher-than-average water levels had been recorded in Aklavik and there is “very high snowpack throughout the Peel River basin and Mackenzie Delta.”

In an environment like the Mackenzie Delta, the GNWT’s report added, flooding will be “very dependent on how the ice breaks up and if and where ice jams occur.”

Elsewhere

In the vicinity of Fort Smith, the Taltson and Tazin rivers were said by the territory to be flowing at a rate roughly half of that recorded a year ago. Snowpack in both areas is normal, the GNWT said. Flow rates on the Slave and Peace rivers are average.

A GNWT graph shows Great Slave Lake’s water level in Yellowknife Bay has dropped from last year’s high but remains above average. (Data up to April 21, 2022.)

In the North Slave, low snowpack “will likely result in lower flow on local rivers,” the territory stated.

Water levels on Great Slave Lake “remain high” according to the GNWT but have dropped slightly “from the extreme levels recorded in the summer of 2020 and spring of 2021.”

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