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NatureSpeak Articles

Whistler’s hydrologic regimes and the upcoming fire season

The cycle of water and wildfire: Our mountains, streams and fire seasons are deeply intertwined. Photo by Dana Wrigley

Ah, the glorious signs of spring! The snow is melting, and streams are flowing. Isn’t it magical to have all the picturesque streams flowing through Whistler? But wait, there is more to these streams than just scenic beauty and recreation. They can give us hints about the upcoming fire season!

Every stream has a unique annual rhythm, resulting from the amount and form of water that flows into that stream system. Both short-term weather and long-term climatic patterns, like the familiar El Niño/La Niña, can help us predict how much water will be flowing and where it is coming from. This past winter, for example, we all experienced the effects of a strong El Niño winter with milder temperatures and less snowfall than typical- and boy did the snowpack reflect it!

The health of Whistler’s many ecosystems relies on these annual rhythmic patterns of stream flow. When these patterns shift, nearby ecosystems feel the ripple effects. We call these fluctuations in stream flow hydrologic regimes and in BC, we categorize them based on those most influenced by rain (pluvial system), snowmelt (nival system), or glacial melt. In Whistler, our streams are mainly influenced by snowmelt and glacial melt systems giving us higher flows in spring through early fall and lower flows in the winter. The melt of annual snowfall precedes the melt of glaciers, allowing for a consistent supply of water during the warmest months of the year.

The rhythm of Whistler’s stream flow changed this past winter. Warm temperatures and large amounts of rain in early February washed away a lot of the snowpack that otherwise would have melted and gradually entered our streams. This reduction of water retention in Whistler’s hydrologic systems, coupled with an anticipated increase in summer temperatures from climate change could lead to drier conditions for not only this summer but subsequent seasons as well.

Moisture in plants, soils, and the atmosphere are all important factors in maintaining a fire- resistant forest. In the winter, many plants die back or go into ‘sleep’ mode but come spring, they wake up thirsty, ready to take up and hold water. But February’s early rainfall meant the plants weren’t quite ready to drink in all the water entering the streams, so much of the water vital to the forest washed away. Consistent water supply keeps the forest soil hydrated, acting like a sponge to filter and retain water and nutrients. If our snowpack runs dry earlier than usual, our forests’ ability to act like a sponge will decrease. This could lead to parched soils from the topsoil layer deep into the ground and drought stressed plants, creating perfect fuel for wildfires.

Speaking of wildfire fuel, the type and availability of it greatly influences both the intensity (amount of heat energy produced) and severity (amount of plants/infrastructure burned). An increase in the density of dead plants and dry logs provides more easily ignitable fuel. Dead standing trees as well as dead branches close to the ground can turn fires into canopy climbing monsters, spreading faster than you can say “smokey the bear”. Dry soils turn surface fires into a sprinting race and can even lead to ‘zombie’ fires that smolder underground throughout the winter and can reignite the following summer. Scary!

The connection between winter conditions, stream flow, the upcoming fire season and the future of our mountain sports are deeply intertwined. Increased winter temperatures and rainfall mean less snowpack to maintain typical stream flow, leading to less moisture in our soils and forests. Dry, warm conditions set the stage for wildfires that are not just bigger but nastier too. And this season's change in hydrologic rhythm isn’t a one-off; as nature’s patterns change climatically from the ‘norm’, our forests will likely become hotter and drier, making each wildfire season a bit scarier.

If you are a homeowner or renter in Whistler and would like to help mitigate the impact of wildfire, consider checking out the strategies suggested from FireSmart BC. The FireSmart BC program has put together varying levels of protection that homeowners can apply to help FireSmart their homes. From something as simple as ensuring your gutters and decks are cleaned of leaves and plant debris, to planting fire-resistant plants and installing fire resistant building materials. FireSmart assessments are free in Whistler and can be booked at Whistler is surrounded by forest, right up to the doorsteps of our homes. By FireSmarting your home, you can help protect your community and the surrounding forests.

Written by Dana Wrigley


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