March 21, 2014
Scientists unravel effects of climate change on Bow River
World Water Day: Less runoff from mountains and more evaporation will decrease water supply
For millennia, southern Alberta has been caught in a cycle of drought and floods. And, over the next 50 years, climate change scientists aren’t sure whether we will see less rain or more, but either way, late-summer water levels in the Bow River are likely to decline.
“With climate change, most of the world is getting warmer and it’s expected to get warmer with a few exceptions, says Shawn Marshall, the Canada Research Chair in Climate Change in the Department of Geography in the Faculty of Arts. “With precipitation, whether you’re expecting more or less than what you’re used to, really depends on where you are.”
For most of Canada, including central and northern Alberta, scientists expect there will be more precipitation — it will get wetter. South of us, in Montana and beyond, it’s expected to become more arid. “But for southern Alberta, it’s not quite as clear,” says Marshall, who is on sabbatical with the University of Geneva climate research group. “Calgary is one of those places where the climate model forecasts disagree as to whether it’s likely to get warmer and wetter or warmer and dryer.”
More rain in the summer when agriculture and other demands are high would help the water supply in the Bow. But increased precipitation the rest of the year is less helpful because, as we’ve seen, “We don’t have much storage in the system.”
Less run off from mountains
Meanwhile, “it’s pretty clear” that the glaciers and snowpack in the mountains west of Calgary are declining. “There will be less water coming from those sources,” says Marshall, whose research group measures snow and ice melt, how the glaciers are changing, and how much glacier runoff is coming into the rivers.
“At the glaciers, the rivers are gushing, they are a huge source of water,” Marshall says, “But by the time you get downstream to Calgary or Edmonton, there is not that much glacier water in the rivers. In the Bow, the average for the year is only 2 or 3 per cent.” The other 97 per cent of the water in the Bow comes from rain and snow, much of it routed through the groundwater system.
More people and industry are coming to southern Alberta and the Bow River’s capacity to serve everyone is already stretched — the province placed a moratorium on new water licences for the Bow and several other rivers in 2006 — there’s already not enough water to go around.
“Not many people expect the quantity of water in the Bow River to go up and it might continue to decline with climate warming, but at the same time our population keeps going up,” says Marshall. “I think the next big drought cycle, whenever that comes along, we are going to realize how tight the water supply is because we won’t have much as water coming from the mountains as we used to.”