BC Hydro has confirmed prolonged water spills from the W.A.C Bennett and Peace Canyon dams that are flowing into the Peace River. 

The release, which began July 17 and continued until Aug. 18, was a result of higher-than-normal snow melt and rainfall.

A sustained release from the Peace Canyon and W.A.C Bennett dams occurred from July 17 to Aug.18 2020. Wikimedia Commons photo

Bob Gammer, a spokesperson for BC Hydro, said that the water flowing into the Williston reservoir from rain and snowmelt, was 20 per cent more than normal. 

During normal activities at the Peace region facilities, the water flowing past Site C – a construction site on the Peace River where BC Hydro is building a new dam and generating system – is typically between 1,900 and 2,000 cubic-metres per second (m³/s). During the release over the last four weeks, the water flow has fluctuated from 2,250 m³/s to 2,500 m³/s.

In addition to having to release water from a larger-than-normal rainfall and snowmelt inflow, BC Hydro is working to create buffer space at their sites in case of more rain, which Gammer says they are expecting. 

“What we’ve been doing so far is preventative,” Gammer said. “When we talk about setting something aside for a rainy day, that’s exactly what we’re doing.” 

Since dam construction can only take place on dry land, BC Hydro has to divert the water flowing past Site C with hillside tunnels on the north bank of the Peace River. While many of the factors at play are unpredictable, Gammer said the idea of creating buffer space is to be able to keep control over the water flowing through the river diversions. 

“We can’t control everything but we can control some of it, so that’s what we’re trying to do,” he said.

As the Slave River and Great Slave Lake in the NWT are upstream from B.C. waterways, the two jurisdictions have been connected through a trans-boundary water agreement since 2015. This prolonged spill is in addition to a release at W.A.C Bennett dam overnight July 12-13.

Rick Pattendon, a professional fish biologist with Mainstream Aquatics Ltd. in Alberta, said that spill operations have the potential to impact fish habitat and aquatic systems. In this case, however, he said the spill’s capacity to change water temperature “likely is not sufficient to affect aquatic organisms because the change will be within the normal seasonal range experienced by the river.”

On the spill’s possible affects on the Peace River’s total gas pressure (TGP) – another variable for aquatic systems – he said spill operations may increase the concentration of TGP in the river, but couldn’t say whether that would be harmful to fish without more information from BC Hydro.

“In general, high river flows that are within the range of typical annual flood flows for a river system are not considered detrimental to the aquatic environment,” he said.

BC Hydro will be required to monitor water temperatures, TGP concentration and flows of the Peace River during their spill operation.

While water releases are a normal part of hydro activities, a prolonged spill like this one has only happened twice before in the last 20 years at the Peace region facilities.

Natalie Pressman

Natalie is a graduate of Carleton University’s journalism program. She has since held contracts working with an NGO in Vietnam and with Journalists for Human Rights in Iskatewizaagegan #39 Independent...

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  1. Let me start by saying that the Slave River and Great Slave Lake are downstream from the Bennett Dam and that the effects on our communities and the aquatic environment are substantial and problematic. Domestic harvesting on the Slave River has been all but completely halted by the high water. Low areas along the River are all flooded, the banks are all silted over by the high water and community boat launches have been practically destroyed by the high water eroding banks. Cabins have remained flooded most of the summer and will have to be destroyed as waters remain near spring flood levels.
    Great Slave Lake has an increasingly growing level of plume related to the high levels of water flowing into it. Yes the whole basin water levels are much higher than normal but the Slave River being flooded by the upstream Bennett Dam releases has significantly caused excessive slit levels to flow into the pristine Great Slave Lake where it’s now affecting their fishery as well.
    I would tend to postulate that the Site C Dam is also contributing to the problem with silty materials being distributed during it’s construction.
    The fall domestic harvest along the Slave River will probably also prove to be greatly affected by these high waters, nevermind the problems these levels have caused to nesting pelicans and other shore birds with the releases flooding their nesting sites. The regularly used Pelican feeding areas are still under water and thus have forced the Pelicans to move from their natural habitat.
    The Bennett Dam has yet to provide a public communication explanation of their actions to the NWT Public and has brobably poorly monitored their situation leading to these knee jerk releases affecting Northerners downstream.
    They should be providing compensation to affected communities and individuals who haven’t been able to practice their inherent rights to domestic harvesting along the watershed because of these releases.