NWT high water levels mean trouble for some, fun for others

Last modified: July 16, 2020 at 5:02pm

This week, the Great Slave Lake water level gauge in Yellowknife Bay sat 29 cm above the average level for any past July 14 in the territory’s records.

Tuesday’s reading in Yellowknife Bay supports the observation that water levels across the lake, and in the rivers feeding it, are the highest some residents can recall seeing.

High water means more debris like floating trees, but local canoeists and kayakers said the current levels were also a “good thing” for their outings.


Meanwhile, an entomologist with experience in the NWT said higher water levels have the potential to reactivate mosquito eggs that could have lain dormant for up to seven years – providing one explanation for what is, anecdotally, an unusually buggy summer.

The Department of Environment and Natural Resources (ENR) says a reading of 157 metres above sea level for Yellowknife Bay on Tuesday is the highest for that date since comparable records began in 1972.

British Columbia’s Bennett Dam was created in 1972, which shifted the average, maximum, and minimum daily water levels on Great Slave Lake – and is why records for water level only go back that far.

The water in Great Slave Lake is abnormally high for this time of year and has been above average since March, according to ENR’s data.

Measurements on Wednesday suggested the water in Yellowknife Bay this year is about 69 cm higher than it was in 2019.


About 75 percent of the water in Great Slave Lake flows from the Slave River, with the main tributaries being the Peace and Athabasca rivers.

Why so much water?

ENR told Cabin Radio there were high snowpack volumes this year in northern BC, northern Alberta, southern Yukon, northern Saskatchewan, and the NWT’s southern areas – which then had a late but rapid-onset melting period. 

Coupled with more recent rain, the result was rising water levels.

In addition to this, between 2014 and 2016 some lakes and rivers in the south of the territory had dry conditions, causing tributaries to stop contributing water downstream. These areas have recovered and have likely reconnected, feeding into larger rivers once again. 


As a result, rivers like the Hay River and Liard River are also seeing high water levels.

On July 15, NWT Parks announced those levels would force the Alexandra Falls river area to remain closed until further notice.

High water levels on Back Bay in Yellowknife on July 15, 2020

High water levels on Back Bay in Yellowknife on July 15, 2020. Sarah Pruys/Cabin Radio

Cameron Beaverbones, president of the Northwest Territories Fishermen’s Federation, said there had been no impact on his catch but he was having to take more precautions on the river, as there is a lot of debris in the water. 

“There’s just lots of logs floating out there. It’s terrible to run into the logs,” he said.

Beaverbones said docking boats is trickier as the water is faster and sometimes spills over the dock. 

“The water is level with the loading ramp, it’s sometimes flowing over the ramp.”

For some paddlers, good news

The paddling season has been off to a good start, said Jackpine Paddling owner Dan Wong, allowing more opportunities for whitewater activities than in previous years. 

“Everything’s high. It’s rocking, it’s a lot of fun,” Wong said.

Wong added he knows many people in the North are affected by the high water and he hopes the levels will subside but, for the time being, it has been good for his business.

Operating from Yellowknife, Jackpine offers trips on various rivers and bodies of water around Great Slave Lake.

Wong says low water in previous years made some rivers too shallow and rocky to pass through, meaning more cumbersome portages with canoes and kayaks.

“We’ve had a lot of big rapids and have had a lot of people through our paddling courses,” he said.


One other group of NWT residents is enjoying the water this summer: mosquitoes.

Taz Stuart, an entomologist who has worked a number of seasons in the NWT, said rising water allows eggs that haven’t hatched for as long as seven years to be reactivated.

Some female mosquitoes lay their eggs in depressions in the landscape that can easily fill up with water, according to Stuart. They can hatch and become full adults in as little as seven to 10 days. 

“The more rain there is and the hotter it is, it’s more likely you’re going to have a good hatch of mosquitoes off of those standing water bodies,” he said.

Mosquitoes continue to lay eggs throughout the summer so, as temperatures and precipitation increase, more waves of mosquitoes will appear, according to Stuart.

“A glass of water in your backyard, about 500 ml, can produce several hundred mosquitoes in as little as three to five days if it’s very warm and humid,” he said.

Stuart added he knows mosquitoes are a nuisance for humans and animals in the North, but they play an important role in some ecosystems. 

“Most people don’t know why they’re here, but they have a purpose. They are a part of the food web for other insects and animals,” he said.

Correction: July 16, 2020 – 16:58 MT. Due to an editing error, this article initially stated that the Yellowknife Bay water level gauge this week “sat 29 cm above the level for any past July 14.” It in fact sat 29 cm above the average water level. The word “average” was omitted by mistake.