Scientist grades water risks from wildfires; prairies at top of list

A helicopter dumps a load of water on the Philpot Road fire outside of Kelowna, B.C., Monday, August 28, 2017. The Canadian prairies top a newly developed index of places where wildfires could threaten freshwater supplies. THE CANADIAN PRESS/Jonathan Hayward

EDMONTON - The Canadian prairies top a newly developed index of places where wildfires could create freshwater supply risks.

"We are a population depending on water coming from a fire-prone area," said Francois-Nicolas Robinne, a University of Alberta geographer whose research has just been published in the journal Science of the Total Environment.

Larger and more frequent wildfires are one of the more commonly anticipated effects of climate change, as warmer weather dries forests out.

Those fires have significant effects on freshwater. Burned-over areas can be prone to floods, mudslides and contamination.

All of those create problems for downstream users accustomed to reliable, predictable, relatively clean flows. They also have major impacts on plants and animals living in the watershed.

Robinne said his index is the first to try to assess those risks on a global scale.

"We have done forest fire hydrological research for 40 years, but it's at the scale of a hill slope," he said.

Robinne combed available information from around the world detailing everything from local soil types to precipitation and weather patterns. He looked at topography, lightning strike patterns, runoff, human settlement, forest age, vegetation, wealth, environmental and human water needs — a total of 33 different global databases, all crunched together and weighted.

"It's amazing what you have, but it takes some time to gather everything," Robinne said.

The result was a colour-shaded map that shows the relative risk that wildfires present to freshwater supplies around the world.

One of the areas at highest risk was the vast belt of forest and parkland that rims Canada's Great Plains and extends from Manitoba to Alberta.

"All the factors are here," he said.

The boreal forest is notoriously prone to wildfires, and in fact depends on them to remain healthy. There's also a lot of water in those forests that could be affected by a fire.

And all that water drains out from the mountains, heading east to dozens of cities and towns that depend on it.

Robinne is careful to point out his index assesses risk and doesn't make predictions.

"(Problems) may not happen," he said.

But the risks are real.

His paper points out that seven years after a 2002 fire, Denver had to spend $30 million to dredge sediment and ash from the city's reservoirs. In 2014, Sydney, Australia, had to shut a water treatment plant after heavy ash contamination.

Scientists and governments are just starting to address the risks, Robinne said. His work was partly funded by Natural Resources Canada and the Global Water Institute at the University of Saskatchewan.

As climate continues to change, planners have to start taking such risks into consideration, said Robinne.

"I'd like those big agencies that are involved in water management to stop and think about it."

— Follow Bob Weber on Twitter at @row1960


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