Great Slave Lake water level nearly back to normal, but will it last?

The water level in the NWT’s Great Slave Lake is rebounding after years of being well below average, the territorial government says.

“Great Slave Lake water level has been rising since mid-May and is currently average to just below average, after being well below average consistently since July 2023,” the latest hydrological bulletin reported on Wednesday.

Across most of the NWT, water levels “are generally higher than the levels observed at this time last year,” the bulletin added, though that isn’t the case everywhere. Great Bear Lake and the Great Bear River remain below average, for example.

“We had a lot of snow over the winter in some key basins in southern and western parts of the Mackenzie River basin. That’s delivered an awful lot of water to the Mackenzie River basin and Great Slave Lake and it’s pushed those water levels back up into average levels, which is great news,” said GNWT senior hydrologist Anna Coles.

While this is a welcome development after years of drought in many parts of the territory, there are question marks over how long it will last.

The return of near-normal water levels in many parts of the NWT is coinciding with the broader onset of the El Niño climate phenomenon, where warmer ocean surface temperatures in the Pacific Ocean can disrupt atmospheric circulation elsewhere.

Coles said that introduces uncertainty about where water levels go from here.

“How the rivers and lakes continue to respond really depends on the sorts of weather conditions we see over the summer, in terms of rainfall in key basins but also temperature – how much evaporation we’re going to see from the land and from the rivers and lakes,” she told Cabin Radio.

“El Niño brings warm and dry conditions to this part of the world. They’re calling for El Niño to rear its head again toward the end of the summer, which certainly might not help sustain those nice water levels that we’re seeing on Great Slave Lake now – but it’s a little early to say.

“Freshet is so key, so we’re keeping our fingers crossed for another great snow year this winter that can help the recovery for next year as well.”