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," Clayton Szafron said. "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.
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, Alta., 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.
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," said Garth van der Kamp, an Environment Canada scientist. Eight of the 10 lakes he examined in Alberta and Saskatchewan are in long-term decline, some 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," said 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.