What will filling the Site C reservoir do to NWT water levels?

Dënesųłiné Elder Francois Paulette says the Slave River that flows by him is “not the way it used to be.”

Paulette, who is a member of the Smith’s Landing Treaty 8 First Nation, sits on the Elders Wisdom Council for Keepers of the Water, a a collective of Indigenous and environmental groups focused on the Arctic Ocean’s drainage basin.

He said the WAC Bennett Dam, a large hydroelectric dam built on the Peace River in northeastern BC in 1968, has negatively affected the Peace-Athabasca Delta.

Now Paulette is worried about the potential downstream effects of Site C, a new hydro dam nearing completion on the same river. The Peace River flows into waterways in Alberta, then the NWT.

“The Peace River Delta is practically dried up and, downstream, we’re in about the same situation,” Paulette said.

“The cost is not just to the environment. It’s cost to the human life and all the living things that live in the water.”

While some First Nations in northern BC were compensated for the impact of the Bennett Dam and its associated Williston Reservoir, Paulette noted First Nations downstream in the North were not.

“The unfortunate side is that people will never be compensated,” he said.

BC Hydro began filling the reservoir for Site C late last month, a process expected to take two to four months. The provincially owned utility has said the dam’s first generating unit will come online in December and all six units are expected to be in service by fall 2025.

Paulette pointed out that downstream water levels are already extremely low, a problem that he said will be exacerbated by filling the reservoir.

The effects of those water levels have been deeply felt in many parts of the NWT, such as the cancellation of resupply barges to the Sahtu region this summer, which has made the cost of bringing freight to those communities more expensive than usual.

“It’s unfortunate. People, they do not know what they’re doing. It’s just plain as that,” Paulette said.

“They have no spiritual ties to the water, they have no spiritual connection to the land. So they just continue to abuse Mother Earth and the water and the people, First Nations.”

Former Dene national chief Bill Erasmus said the Athabasca and Mackenzie deltas used to have “the best muskrat hunting and trapping.”

After the Bennett Dam was built, he said, the lack of muskrat meant a parka factory in Aklavik had to close.

“That affected people economically. The trapping basically was shut down,” he said.

“This has affected people in a number of ways and the people upstream need to be responsible for what they do to people downstream.”

When it comes to Site C, Erasmus said water is a treaty right and the dam is located in Treaty 8 territory. He, too, wonders how the project could affect water levels and water quality in the NWT.

Water levels could drop 8.5 cm, GNWT says

The NWT government has documented the shift across many waterways from some of their highest-ever water levels just a few years ago to some of their lowest on record.

The territory attributes that transformation to extreme drought since the summer of 2022 – a drought driven by a lack of precipitation in parts of the NWT, northern Alberta and northern BC.

Ryan Connon, a hydrologist with the territorial government, said water levels on Great Slave Lake have dropped by more than 120 cm due to climate-driven drought over the past two years.

He projects filling the Site C reservoir will temporarily cause the lake to drop up to another 8.5 cm.

Connon said water levels on the lake normally decline at this time of year anyway, so the drop from filling Site C’s reservoir will add to that natural decrease.

“Right now, the water levels on Great Slave Lake are the lowest they’ve ever been on record for this time of year,” Connon said. “If water levels continue to drop on Great Slave Lake, we could hit another all-time low this winter.”

Connon said the effect on the Slave River of filling the reservoir will be “more transient.”

Fish monitoring in Slave River

Once the dam is operational, Connon said the overall impact of Site C’s reservoir on Great Slave Lake and Slave River water levels will be similar to that of the Bennett Dam’s Williston Reservoir.

“In the summer, flows are lower than they would be otherwise,” he explained of the Williston Reservoir’s effect. “In the winter, flows are higher than they would be otherwise. But we don’t expect to see a more significant change than what was happening before.”

During a recent public briefing on low water levels, territorial officials said the NWT’s environment minister had asked BC Hydro if filling the Site C reservoir could be delayed, given the low water levels on Great Slave Lake. Officials said the utility responded that it did not believe there would be an impact on downstream water levels.

The NWT government now hopes to start an information-sharing agreement with the province regarding the dam. The current transboundary water agreement between the NWT and BC applies to the Liard River, but not the Peace River, which does not flow directly into the territory.

Thomas Bentham, a spokesperson for the NWT’s Department of Environment and Climate Change, said it “does not expect any impacts to ecosystem health in the NWT related to filling of the Site C reservoir or over the long term.”

However, Bentham said changes to NWT water quality related to Site C could include elevated levels of nutrients and metals. He said the territorial and federal governments will continue to monitor the Slave River and report on any changes.

Bentham added the NWT government and community partners plan to monitor biological indicators this fall, such as fish, in the Slave River. He said the results will be shared publicly.

‘Negligible’ effects beyond Peace Point, BC Hydro says

BC Hydro has said once operational, Site C will be a cost-effective source of clean electricity that will be able to provide enough power for nearly 500,000 homes or 1.7 million electric vehicles.

Bob Gammer, a spokesperson for the utility, told Cabin Radio that while filling the reservoir, BC Hydro expects any “notable changes” to occur only early on, and in the area immediately downstream of the dam within BC.

“We recognize drought has impacted many areas of Canada, including British Columbia, Alberta and Northwest Territories. This has resulted in lower-than-normal river flows and lake levels the past two years,” he wrote.

Once operational, Gammer said the effects of Site C are “expected to be negligible” beyond Peace Point, Alberta.

“Two BC Hydro dams and generating stations have been operating for over 40 years upstream of Site C, so flows downstream will be very similar to those of recent decades when Site C begins full operation next year,” he wrote.

Gammer said BC Hydro is working with the NWT government to provide the territory with project data it has requested.