As Williston Lake - Bennett Dam's reservoir in northeastern B.C. - reaches its maximum capacity, the provincial government says it doesn't have any plans to spill water downstream. - photo courtesy of Andrew Jorgensen |
Southern reservoir full but Mackenzie runs dry
As barges run aground in record-low water levels, the B.C. lake that feeds the waterway sits less than an inch from capacity
Elaine Anselmi
Northern News Services
Monday, October 12, 2015
NORTHWEST TERRITORIES
Just north of Fort Good Hope on the Mackenzie River, barges are turning back due to low water levels and boaters are left weaving around sandbars.
Environment Minister Michael Miltenberger says downstream effects of dam projects in B.C. are being monitored in Alberta and the NWT. - Elaine Anselmi/NNSL photo |
"Right now, if you're going to go through there, you're best to be guided by somebody who knows where to go," said Fort Good Hope Chief Junior McNeely, adding smaller creeks that feed into the Mackenzie are high because of consistent rainfall over July and August. "With all this water, you'd think the Mackenzie would go up."
Further south along the river, Deh Cho Grand Chief Herb Norwiegan described to News/North last week water levels so low people are damaging their boats.
"People are lowering the lower end of their outboards and busting their props," he said.
Over on Great Slave Lake's north arm, waters dropped a full 10 centimetres on a single day on Sept. 27.
While there are several reasons for low waters in the NWT, including a multi-year drought, territorial government representatives are also acknowledging the impact of the W.A.C. Bennett dam in northeastern British Columbia. The dam holds water from flowing north up the Peace River into the Slave River and eventually Great Slave Lake and the Mackenzie River in order to generate power for B.C. residents and sell excess power to jurisdictions in the United States.
In fact, while water levels in the Mackenzie River basin sit near historical lows, Williston Lake, the man-made reservoir sitting behind Bennett dam, sits less than an inch from capacity - a measure set by the Government of British Columbia's comptroller of water rights. Once reached, B.C. Hydro is required to spill water from the reservoir into the Peace River.
Opening the dam's spill gates rather than running water through the dam turbines and powerhouse is rare - the last spill occurred in 2012.
"Any hydroelectric utility wants to avoid spilling water because water is energy, essentially," said Bob Gammer, spokesperson for B.C. Hydro. "If we spill water, we lose the opportunity to use that to make electricity."
In late September, Environment Minister Michael Miltenberger talked to News/North about the effects of Bennett dam on NWT's water.
"There was an impact, more on flows, seasonal flows were gone, the annual flooding in the spring that type of thing disappeared so they had planned releases but it's not the same," said Miltenberger. "So there was an impact and it was felt all the way up - the Peace-Athabasca Delta was the biggest area of impact."
Peace-Athabasca Delta area is the major contributor to the Slave River, flowing into Great Slave Lake. The Slave, which contributes three quarters of the annual input to Great Slave Lake, receives 60 per cent of its annual flow from the Peace, Shawne Kokelje, hydrologist, for Environment and Natural Resources told News/North in an e-mail.
Generally speaking, Kokelje said hydro-electric dams reduce high flows and increase low flows downstream.
"Since 1971, when construction and filling of the Bennett dam were completed, there have been changes to the annual hydrograph of the Slave River. Winter flows are higher (by approximately 75 per cent) and spring peak flows are lower (by approximately 20 per cent)," she said. "It is important to note that the total amount of water flowing into the NWT has not changed, just the timing of when the water arrives."
Since June, Great Slave Lake has been at or near minimum daily levels.
"While low amounts of snow and rain in the North Slave region have led to historic low water levels in local lakes and river basins - for example, Yellowknife, Snare and Cameron rivers - it is the extent of dry conditions into northern B.C and Alberta that has resulted in low water levels in much of the upper portion of the Mackenzie River Basin," she said.
"Overall, there are many factors that can affect water quantity. The two most significant are development and climate change."
Downstream from Bennett dam Site C is under construction - and the B.C. Government has been somewhat at odds with NWT leaders on what impact it will have in the territory.
Back in the 16th Legislative Assembly, Miltenberger said two ministers from B.C. came up to meet with himself and now-Premier Bob McLeod over the development of Site C.
"They were at the time of the opinion that there was no impact, there wasn't any impact that required consultation much farther downstream than 12 kilometres. Of course, we did our best to dissuade them of that and show that Site C would have an impact all the way to the Arctic Ocean and we wanted to be on record that it is a concern, that the flow issue needs to be very carefully monitored," said Miltenberger.
"If we had our druthers, they would not have built Site C but they have decided to, now we have to make the best of that decision."
As well as the territorial government, First Nations from B.C., Alberta and the NWT brought concerns forward to a federal-territorial Joint Review Panel on the Site C project. The Deninu Kue First Nation (DKFN) presented to the panel in January 2014, outlining the significant changes and "drying up" of the Slave River watershed and subsequent impacts.
"By all accounts these changes commenced in the 1960s and increased in intensity in the 1980s: 'recent' times relative to the DFKN's presence in the watershed since time immemorial," the submission reads. "The land users attributed the changes primarily to the commissioning of the Bennett and Peace Canyon dams."
In April 2013, the GNWT submitted comments to the B.C. government on Site C.
The comments cited a 1997 study that found, "the flow and sediment loads at the Slave River Delta had decreased after W.A.C. Bennett Dam was built (in the 1960s). Major findings of the project indicated that sediment loads decreased by 33 per cent, reducing the formation of the Outer Delta landforms; and that a drier, less productive environment was forming in the delta, indicated by the change in the plant community."
This year, the GNWT struck a transboundary water agreement with Alberta that covers rivers, such as the Slave, that feed into the territory.
The government is working on a similar agreement with B.C. that would cover the Liard and Petitot rivers, but discussions of the headwaters of the Peace are left between Alberta and B.C.
"They have some provincial-territorial independence, which we all jealously guard. They have their own plans for the water they've stored - I imagine because they have their own challenges. As the water issue becomes more critical, yes, there are going to be ongoing discussions and they'll be the formal processes, they'll be the political process."
Asked about the disparity in water levels between Williston Lake and rivers downstream from the Bennett and Peace Canyon dams, Miltenberger recognized the cause for question.
"At the face of it, Williston being full and downstream being wanting for water, well, 'Drain off half your water and put it back into the ecosystem', your counter-intuitive assumption would be something like that," Miltenberger said.
But it's not that simple, and a full picture of how dam infrastructure affects water levels downstream is not completely clear.
"The key for us," Miltenberger said, "is to get the full understanding of what the numbers are in the dam."
Fact file
B.C. dam facts
W.A.C. Bennett dam
Located: On Peace River, northeastern B.C.
Began generating electricity: 1968
Size: 2 km wide, 183 metres tall
Maximum regulated capacity: 2205 feet above sea level
Current water level: 2,204.4 feet above sea level
Minimum water discharge level: none because it is upstream from Peace Canyon dam, with minimum discharge of 283 cubic metres per second
Minimum discharge level set by: B.C. Water Comptroller
Alberta and NWT consultation requirements: None
Site C dam
Located: On Peace River, downstream from Bennett dam
Scheduled to begin generating electricity: 2024
Size: 1.05 km wide, 60 metres tall
Recommended minimum water discharge level: 390 cubic metres per second
Set by: B.C. Water Comptroller
Alberta and NWT consultation requirements: Consultation with Alberta government recommended by federal-provincial-territorial joint review panel
Source: Government of British Columbia
