Deglaciation will cause water shortages for Alberta’s Bighorn Dam and other sites

Alberta’s largest water reservoir, the Bighorn Dam, is among four locations in the province most at risk of summer water shortages due to future glacier loss, according to new research from the University of British Columbia.

In a study outlined in Nature Climate Change, researchers examined how deglaciation in Alberta will affect regional water availability throughout the province. Current models predict that Western Canada will lose 70 to 90 per cent of its glacier ice volume by 2100.

In the first study of its kind, researchers analyzed patterns of streamflow in glacier-fed rivers and identified which communities rely on them for source water. Previous work in this field has often relied on computationally expensive and challenging studies of individual glaciers.

By both projecting how deglaciation will affect stream flows and identifying where communities source water from, they were able to pinpoint where the largest changes to water supply are most likely to occur. Their analysis revealed that the most vulnerable areas to August shortages include the Bighorn Dam, which serves more than 1 million people and creates Abraham Lake along the North Saskatchewan River; the town of Rocky Mountain House, which is downstream of the Bighorn Dam; the hamlet of Lake Louise, part of the Canadian Rocky Mountain Parks UNESCO World Heritage Site; and the town of Hinton.

“These places are going to see substantial changes to their water supply,” said lead author Sam Anderson, PhD candidate in the UBC department of earth, ocean, and atmospheric sciences. “That will include having lower August flows on average, and a larger range of possible flows year to year. It's not that the rivers will run dry and they'll have no options, but these communities and locations will need to look for different water management strategies in the future that will help them manage the late summer period.”

To reach their conclusions, the study’s authors reviewed data on water flow for 194 rivers across Alberta and analyzed how their patterns differed. They found that, year-to-year, glacier-fed rivers had more stable water flows in the month of August, regardless of average yearly temperatures.

“Typically, by August, non-glacier fed rivers were below their yearly average in terms of how much water would flow into them, but glacier fed rivers had relatively high August flows consistently year to year,” said Anderson. “In a very hot and dry year, there would be more glacier melt in the river, which kind of counteracts the lack of rain. But in a cool and wet summer, there would be less glacier melt, which would counteract the surplus of rain.”

Anderson collected information on water sources for nearly 600 communities, and determined which relied on glacier-fed rivers. He found that, in the absence of glacier runoff, the Bighorn Dam will experience the largest decrease in average August flow, but the smallest increase of variability. The town of Hinton is projected to have the smallest change in August flow, but a large increase in variability. Average flows and variability for the hamlet of Lake Louise will be between those for Hinton and the Bighorn Dam. All will experience unprecedented numbers of days of below-average flow.

Anderson also discovered that eight communities located near glacier-fed rivers, including Jasper and Banff, will be shielded from the effects of glacier retreat, as they source their municipal water from deep underground aquifers.

“We went in with the assumption that communities in a highly glaciated area would be impacted, but it was interesting to find that that's not necessarily true. That’s why data on municipal water sources are important for understanding water resource vulnerability,” said Anderson.

Valentina Radic, co-author and associate professor in the department of earth, ocean and atmospheric sciences, says the research methods used can be applied to other regions whose municipal water supply relies on glacier-fed rivers.

“Our method is easily transferable to regions such as the European Alps, the Himalayas, New Zealand, and Patagonia,” she said. “All we need is readily available information like streamflow data, instead of the costly and difficult studies of individual glaciers that have informed previous work. The same can, and hopefully will be, done in other parts of the world, where actual data on glacier melt is often not available.”