EDMONTON — Every spring, wardens at Elk Island National Park just east of Edmonton patrol the shores of Astotin Lake to clean up debris exposed by receding water. The junk that shows up on the ever-lengthening beach provides a kind of index for just how long it has been since water levels were that low.
“This year, I found a tire from a Model A car,” says Clayton Szafron. “It’s kind of disconcerting.”
Astotin isn’t alone.
The verdant parkland between Edmonton and Saskatoon was once home to dozens of so-called “prairie pothole” lakes — a type of lake unique to the Prairies that is fed only by rainwater and snowmelt. Now, whether from natural precipitation cycles, land use changes or as a consequence of climate change, most are drying up.
Grass grows under boat docks. Lakefront cabins are now field-front.
At Cooking Lake, southeast of Edmonton, float plane pilots who have safely landed for decades are warned to watch for obstacles created by low water levels.
In Tofield, Alberta, the annual Snow Goose Festival — a popular tourist event based on the arrival of tens of thousands of migrating snow geese — had to be scrubbed a couple of years ago, after Beaverhill Lake nearly disappeared.
“People would come from Edmonton to Tofield, so they’re already driving an hour or so, then we’d have to put them on a bus and drive for another hour or so to find geese,” says area naturalist Deanne Cox.
Six out of the 10 such lakes in Central Alberta that are monitored by Alberta Environment are below normal levels by an average of a metre. That doesn’t include Beaverhill or Astotin, which have lost more than one-quarter of their depth over the last decade.
“Most of the lakes have been going down quite significantly pretty much over the whole Prairie region,” says Garth van der Kamp, an Environment Canada scientist who published a paper on the issue in 2008. Eight of the 10 lakes he examined in Alberta and Saskatchewan are in long-term decline, and some of them have been since the 1920s.
Experts hasten to point out that water in these types of lakes has always fluctuated.
Some lakes are stable and some are even rising.
Devils Lake in North Dakota is filling up so quickly that state authorities want to drain some of its waters into the Red River system.
Experts suspect the long-term drying and warming of the prairie ecosystem is the main reason for the shrinking lakes. Data produced by the Prairie Farm Rehabilitation Administration show that, with the exception of a few wet years such as 2005, precipitation in the parkland belt heading southeast from Edmonton has been consistently below normal for a long time.
Land-use practices may also be affecting lake levels in ways not yet fully understood.
The big question is whether the lakes are the temporary victims of cycles that will eventually swing the other way or if they’re being dried out by more permanent climate change.
“There are going to be innumerable consequences (to climate change),” says Cara Van Marck of Alberta Environment.
What is certain is that it will take more than one wet year to refill the prairie potholes.
“If it got wetter for a number of years you could see the lakes rising, says van der Kamp. ”It would take quite a long wet period.“”
“You need to replenish the entire watershed,” says Van Marck.