Upstream wildfires could contaminate Calgary's drinking water — so the city's planning ahead

Wildfire season is getting longer in Alberta every year with climate change, scorching land and polluting the air with thick smoke.

But, the City of Calgary is studying another, perhaps less obvious, impact of wildfires — drinking water contamination.

There haven't been any major fires in the Bow and Elbow river watersheds, upstream of the City of Calgary, for years.

But, there are fears a major fire west of the city could wash burned material into the rivers, impacting the drinking water supply for the city's 1.4 million residents.

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The city has identified large, uncontrolled wildfires as one of the top risks that could impact the city's source water quality — and it's the only one that could cause a dramatic drop in water quality in a short period of time. 

So, the city is studying what can be done to reduce that risk.

"After storm events, there are significant water quality changes on a burned landscape, whether it's from a forest fire, grass fire or shrub fire," said Harpreet Sandhu, the team lead with watershed planning for the city. "The goal is ultimately to continue to provide safe, clean drinking water for Calgarians and to mitigate those risks."

Sandhu said there are a number of possibilities being looked at to keep Calgary's drinking water safe.

Fire isn't going to know any boundaries and neither does our watershed or our water quality.- Harpreet Sandhu, City of Calgary

One is mapping areas upstream where prescribed burns could be done. Another is improving communication with emergency management agencies, so water treatment plants can be kept in the loop and possibly change their operations if needed to respond to wildfire events.

Another option — but a costlier one — would be to upgrade water treatment facilities to more easily process out those contaminants. 

Of course, most areas upstream that impact the city's water supply aren't under municipal jurisdiction.

"I think a lot of this work is about collaboration, because fire isn't going to know any boundaries and neither does our watershed or our water quality," said Sandhu.

"It's not just a Calgary issue."

Sandhu said climate change is causing droughts in watersheds across North America, and devastating wildfires. And while wildfires are most known for causing property damage, the impacts to water quality can last for years.

After fires, water chemistry changes in burned areas can include the concentration of nutrients, sediment, metals and dissolved carbon, all of which are harder to treat and process.

So, Sandhu says it's time to start planning ahead.

"I think that communication piece is going to be really important, because typically when there's a wildfire, we don't think automatically [about] drinking water or risk to drinking water."

A task force is looking at strategies, and suggestions should be ready for the city in the next few months.