Snowpack is above average for Bow River Basin as Alberta flood season begins

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Snowpack above average for Bow River basin
WATCH: River forecasters are keeping a watchful eye on a higher-than-usual snowpack in the Bow River basin. As Sarah Offin reports, flood watch season has begun in Calgary and climate experts are noticing some concerning trends – May 12, 2021

Snowpack isn’t a predictor for floods, but it is a factor and it is above average in the headwaters of the Bow River basin this year.

April measurements from Alberta Environment and Parks in the Bow River Basin vary, from as low as six per cent above average to locations nearing record highs of 87 per cent above average. Mountain snow overall in the basin is 27 per cent above average.

“There were two the 17 sites that came within the top 10 of the historical record and those records go back between 35 and 40 years,” said Collen Walford, a river forecaster with Alberta Environment and Parks. “Keep in mind that those two that were in the top 10 were either equal to, or slightly less than last year.”

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Meanwhile, it appears a cool spring in the mountains is also leading to a slower melt, which can increase the likelihood of rain-on-snow events and lead to flash flooding, as was seen in Alberta’s 2013 flood.

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“It appears that the highest floods — going back 1923, 1932, in the 1800s, 2013, and to some extent, 2012 — have a snowmelt contribution to the rainfall. So it’s snowmelt and rain mixed. To simply get that much flow in the river, you need everything coming into the snowpack as well as the rainfall at once,” said Dr. John Pomeroy, a world-renowned hydrologist from Canmore.

Pomeroy has spent three decades studying ways to reduce the impact of water-related natural disasters.

He is among those paying careful attention to climate trends that could spell more trouble for places, like Calgary, susceptible to flooding.

“What’s concerning is the increase in the intensity of single-day rainfall events in many parts of Canada and the world. And that’s directly been attributed to climate warming. And what we’ve noticed more on the Prairies, in the Prairie provinces, is the increase in multiple day rainstorm events, two to three or four days. And those are the ones that cause flooding.”

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The snowpack is expected to continue to build in the coming weeks.

The province will send crews back out at the end of May for additional measurements.

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