Birds at risk as Prairie lakes dry up

"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.

"We've got some (lakes) that are reaching historic lows for recorded history," says Martin Grajczyk of the Saskatchewan Watershed Authority. "But we're uncovering tree stumps that show they were a lot lower in the past."

Many of these lakes are on the mid-continent flyway, a major highway for hundreds of thousands of migratory birds. Not only do waterbirds such as ducks rely on the lakes, but songbirds flock to the trees and shrubs around their shores.

"Warblers, grosbeaks and sparrows rely heavily on the margins of these things," says Jeff Wells, a leading ornithologist.

The lakes are particularly important to ducks and geese in the fall, when the young make their first trips south and require frequent stops.

"Normally, if you have a drop in water levels you have a drop in the number of breeding ducks," Wells says.

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.

"We know that climate change is happening. We're running models and doing the analysis to try and find out if there's anything that we can prevent or we can do to adapt to our changing realities."

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.

-- The Canadian Press

Republished from the Winnipeg Free Press print edition July 20, 2009 C8