What’s causing the NWT’s low water, and where did the water go?

It’s not dams, firefighting efforts or even underground mine tunnels, despite what the armchair experts on social media may say. It’s extreme drought.

Ryan Connon, a hydrologist with the Northwest Territories government, says that’s the cause behind low water levels across much of the territory.

On Great Slave Lake’s Yellowknife Bay, water levels are their lowest on record for this time of year, leaving some houseboats sitting on the exposed lake bed.

Connon said about 75 percent of water that flows into Great Slave Lake comes through the Slave River and other tributaries, with water flowing out to the Mackenzie River.

“If the Mackenzie River is draining more water than is coming in, then the water levels on Great Slave Lake are going to drop as they have for the past couple years,” he said.

Connon said the southern part of the NWT and northern parts of BC, Alberta and Saskatchewan are all experiencing dry conditions. The region has been in a drought since around July 2022. Drought conditions south of the territory mean less water in systems that gradually drain north.

Over the next three months, Connon said, much of the area is expected to keep receiving less rain than normal. He said precipitation levels may increase in August and September as global weather patterns shift.

So where has the water gone?

Connon said the amount of water that evaporates off Great Slave Lake is relatively small, but evaporation across the entire basin – combined with low precipitation – has led to low water levels. Meanwhile, he said, plants and trees “are sucking up all the water from the soils” on land, with little rain to replenish that reserve.

As for the theory that dams are causing water levels to drop, Connon said the largest regulated portion of the Great Slave Lake basin is the Bennett Dam on the Peace River in northern BC.

According to Connon, last summer that dam actually released more water than was flowing in – meaning water levels on Great Slave Lake would actually be lower than they are now without it.

Meanwhile, Connon said the amount of water used to fight last year’s wildfires “would have essentially zero impact on the low water levels that we’re seeing.”

“The amount of water that moves through a system, and some of the large rivers and lakes, is many orders of magnitude higher than what we would see from water use for firefighting,” he said.

Given the low water levels, Connon said people boating on Great Slave Lake and other waterways should be careful.

“We’re going to see conditions this summer that a lot of folks have not seen before, so be safe out there and let people know your travel plans,” he said.