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How wildfires can have a devastating, long-term impact on nearby water supplies

  • 25 July 2023
  • jherman

Paul Hantiuk · CBC Radio · Posted: Jun 24, 2023 4:00 AM EDT | Last Updated: June 24

Monica Emelko arrived in Fort McMurray, Alta., in June 2016 to help study the impact of the wildfires. She says the devastation to people's homes and lives she witnessed changed her as a person. 

Emelko, the Canada Research Chair in water science, technology and policy at the University of Waterloo, was there to help ensure the drinking supply was safe for consumption as people readied to return to their homes.

Some researchers thought her team wouldn't even be able to detect an impact from the fires because the Athabasca River was already looking like tea before the fires. Heavy rains tend to send hot fudge-looking runoff from the land into the river, making it look like chocolate milk, she said.

Arriving after the fires, Emelko said she could see that hot fudge-looking flow enter the Athabasca's waters as ash, likely carrying nutrients like phosphorous and carbon, made the water supply challenging for treatment processes.

"Those [workers] were living in the water treatment plant, working hard to make sure that people could return to their homes and at least have safe water to drink," Emelko told Day 6 host Brent Bambury.

Canada is in the midst of an "unprecedented" wildfire season and experts say the escalating severity of the fires poses a compound threat to water supplies in their vicinity.

Officials in Nova Scotia have warned about the dangers of contaminates washing into wells. But if you don't rely on well water and live in a municipality or region where the water goes through a treatment plant, Emelko says contamination itself isn't really the problem.

"Drinking water providers do not distribute water unless it meets the criteria for health and safety that are common across the country," she said.

Contaminants strain treatment plants 

From a water treatment perspective the issue is mostly the strain contaminants pose to the infrastructure and supply.

"If the water is difficult to treat, we might not always have as much of it as we want at the quality that we want and need and on-demand."

Algae is one of those potential contaminants, says Emelko. Blooms of cyanobacterial (more commonly referred to as blue-green algae) are becoming a regular occurrence in parts of Canada, as seen in Nova Scotia

Every year after the 2016 fires, she says, there's been an algae bloom near Fort McMurray. Algae can clog filtration and limit the water treatment system's ability to keep up with demand. The infrastructure in Fort McMurray was built decades ago, before algae was a problem.

Algae can also create potential toxins that make people sick, but Emelko says those toxins haven't been found in Fort McMurray, and the drinking water is safe. But she cautions that toxins in the water supply could potentially still emerge.

Uldis Silins, a professor at the University of Alberta with a focus in forest hydrology, says that severe wildfires can affect watershed areas to the extent that health of a nearby river, and even its entire aquatic ecosystem, can change.

"It's when you start to see those impacts downstream where people live in large urban centres that people are really going to start to take notice," he said.

Up and down the food chain

Silins says wildfires can trigger what's called a trophic cascade, an event that indirectly affects an entire ecosystem. He says, in lay terms, it's not much more complicated than your "basic food chain."

Healthy forests intercept a lot of runoff from rain, but when trees are burned or removed from a watershed, you'll get more flow into rivers. That also applies to snowpack melting quicker when tree cover has been eliminated.

The runoff carries natural contaminants — like organic carbon ash or sediments including phosphorus — through a river ecosystem. 

"Phosphorous is particularly important as a nutrient because,in our part of the Rockies, phosphorus is the principle nutrient that limits stream productivity," said Silins. 

He said he's observed that when substantially more than usual phosphorus is added to the system, there's more plant growth and more aquatic insects, and that in turn impacts fish.

"We didn't lose the clean water species, but we had immigration of species that are more tolerant of really degraded water quality. And the overall [species] population levels went up."

In the areas Silins has studied, those impacts have been long lasting.

He researched the severe 2003 Lost Creek wildfire in Alberta for years after it occurred. When parts of Alberta, including Calgary, were then flooded in 2013, his team was in a rare position to chart the impact over a decade.

"Even a decade after the fire, [the flooding] completely reactivated the disturbances, and in fact, produced a seven to almost nine-fold increase in production of sediments — phosphorus and some of these other water-quality contaminants."

Time to adapt

Silins notes that the areas in Alberta he's studying have experienced wildfires for quite some time. It's the severity and frequency that present increasing complications — and it's a global concern.

"I know that there are land managers struggling with this issue and trying all kinds of things on the landscape really all over the world."

Emelko stresses that all levels of government in Canada need better co-ordination, better water treatment infrastructure, and more water monitoring.

"If you don't provide [water treatment plant operators] with any insight as to what's coming down the pipeline or what's coming down the river, literally, that upstream monitoring, you're kind of asking them to do things in the blind."

She said she thinks awareness is bringing a more adaptive mindset to the problem.

"When I started working in this area back in [2004] we couldn't even get funding for this issue. Thankfully, we were able to get some from the government of Alberta, but people kept saying, 'Oh, this is a one-off issue fire. That's not a broader issue that Canadians need to be worried about.' And boy, [have] things changed in a short period of time."