Wildfires pose increasing threat to water quality, experts warn

Following the devastating 2016 Fort McMurray wildfire, local officials faced the formidable task of ensuring drinking water safety for residents. The wildfire significantly increased water treatment costs, as higher chemical dosages were needed to remove contaminants from the Athabasca River.

The wildfire contaminated the Athabasca River with ash from the burnt forest floor, turning the water brown in color and raising dissolved organic carbon (DOC) levels, which reacted with chlorine to produce harmful byproducts within it.

As wildfires become more frequent and severe due to climate change, concerns about their effect on water quality are increasing. A story in the Washington Post states recent research shows fires can dramatically alter watershed dynamics and introduce harmful substances into drinking water.

A healthy watershed depends on vegetation and ground cover to protect the water table, the story states. Rainwater is usually filtered by leaves, grass and soil, but after a wildfire, ash replaces this cover, preventing water absorption and increasing risks of landslides and flash flooding.

Wildfires near homes can jeopardize drinking water quality by damaging PVC water lines, which release volatile organic compounds (VOCs) into the supply. After the fires, it can be difficult to identify damaged pipes, complicating efforts to address contamination.

Just as it was in Fort McMurray, this could be a concern in Jasper where up to half of the town’s buildings were destroyed.

Uldis Silins, a professor of forest hydrology at the University of Alberta who has dedicated over two decades to researching the impacts of wildfires on water in the Rocky Mountain region, said that severe wildfires can significantly affect watersheds and potentially damage the health of nearby rivers and their aquatic ecosystems.

“Healthy forests, undisturbed forests really produce, probably the best quality water that you can have,” Silins said. “After a wildfire, you typically see a deterioration in water quality… because now the grasses and mosses have all been burned away, leading to increased erosion.”

This erosion carries sediment and ash into nearby streams and rivers, introducing harmful contaminants. That ash is rich in organic carbon, an essential nutrient for aquatic ecosystems, but also one that complicates water treatment processes.

Silins told Canada's National Observer that his previous water quality research on the Lost Creek wildfire in southern Alberta is likely relevant to the current situation in Jasper. The forest and geological characteristics in these regions are quite similar, he said.

In Lost Creek, sediment and phosphorus levels in the water rose. These nutrients can stimulate algae blooms, which further degrade water quality and pose health risks to communities relying on these water sources.

Silins notes that recent years have seen an increase in the severity, intensity and size of wildfires, largely driven by climate change. He warns that more frequent and severe wildfires are likely to be a reality in the future.

Travis Kendel, associate director of development and engineering services at the Regional District of Central Okanagan, has seen the significant impacts of wildfires on critical infrastructure — including water treatment in the Central Okanagan — and echoes these concerns.

“Wildfires can result in large-scale lingering impacts to the landscape that trickle down to our drinking water sources,” Kendel said. “Wildfires can introduce new contaminants to lakes and rivers, impact the integrity of underground pipes, and destroy above-ground infrastructure like pumphouses.”

Kendel said the effects linger long after the fire is out. Water utilities and regulators strive to ensure drinking water remains safe, but the process becomes increasingly complex and costly in the aftermath.

“Increased frequency and severity of environmental events, like droughts, wildfires, invasive species and floods, are pushing our critical infrastructure systems to and beyond what they were designed to do,” he added.

Maintaining safe utilities post-disaster or enhancing their reliability for future disasters requires time, funding and skilled personnel, Kendel said. He advises communities to invest in their public utility professionals, collaborate openly with regulators and assess the funding needs for their critical public infrastructure.

Two-thirds of Canadians rely on surface waters, such as lakes and reservoirs, for drinking water, much of which comes from forested areas.