Measuring Winter Snow

Researchers at the University of Saskatchewan recently announced that they had solved the problem of numerically modelling snow distribution over large, topographically complex alpine areas, using a model called the Canadian Hydrological Model (CHM).

Why is this important?

Snowpack is critical for our spring water supplies, and plays a role in spring flooding. If we can accurately measure how much snow is on the ground just before the melt season begins, we can determine how much water it will produce and can predict how fast it will run off given different weather scenarios.

While manual measurements are limited to small areas, this model can be applied over entire basins – there’s even talk of scaling it up to the entire western Cordillera. Modelling is also less expensive than techniques such as LiDar (Light Detection and Ranging technology), which measure snow thickness using instruments mounted on an airplane.

Arctic glacier snow pit.

Who will benefit?

Downstream water users and managers will benefit from knowing the amount of water that they can expect from the spring snowpack, while backcountry enthusiasts will benefit from knowing where avalanches are likely to happen. The model will also be useful in regions with chinook winds, like southern Alberta, as it will be able to predict how much snow is lost over winter to these warm wind events.

How does it work?

The model uses “wind and avalanches, shading by mountains, wind flow over ridges, and vegetation, along with weather forecasts” to distribute snow across the landscape. This is ground breaking because some of these processes are quite difficult to accurately simulate – particularly the role of mountain winds in snow redistribution. The UofS researchers have had to overcome many challenges in simulating these processes – according to the press release, it took one researcher two years to figure out the wind redistribution module.

Wind redistribution of snow.

How do we know it works?

The researchers modelled the 1000 km2 Marmot Creek research basin in Canada’s Kananaskis region, and validated the model output with a combination of LiDAR data collected by a group at UBC and satellite image analysis by a group at the University of Toulouse.

Marmot Creek Research Basin

Want to test it out?

You can go to the UofS’s Snowcast page:, to see the model in action. Note this is just for demonstration purposes, not for use in decision-making. It applies the model to a region that includes the Upper Bow River watershed, above Calgary, Alberta.

What’s next?

UofS principle investigator Dr. John Pomeroy notes that there is interest from UNESCO to use the model globally. “This will allow for better water management, which is certainly what every water management agency in the world wants right now, with our climate becoming more variable,” he said.

One of my graduate students used this model when it was still the Cold Regions Hydrological Model (CRHM), nine years ago. The UofS team has put a lot of work into developing this model for large-scale use, and the wind redistribution algorithms are one of the trickier aspects of the model. I’m impressed that they’ve managed to get it to the stage where it’s being considered for international use.

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