A lake in Sudbury that was intentionally left untouched after damage from mining emissions has managed to make a recovery.

Scientists have been monitoring Clearwater Lake since the 1970s when acid and metals released by nickel smelting operations in Sudbury left the water body all but void of life.

The lake was left to recover on its own so it could serve as a barometer of the environmental health of Sudbury, said John Gunn, the director of the Living with Lakes Centre at Laurentian University.

"It was set aside in Sudbury's official plan as a way to monitor the health of the city," he said.

About a decade ago, small fish started showing up in Clearwater Lake, and last week students on a field course at Laurentian University discovered a healthy small mouth bass population in the water.

Clearwater Lake

Clearwater Lake is located in the south end of Sudbury. (Google)

The presence of multiple fish species means the lake can now be considered recovered, something Gunn attributes to improvements in Sudbury's air quality.

"That's a wonderful indication the lake has passed through the threshold for recovery," he said.

"I think the fish are telling us in some ways we are doing very, very well. The investments in clean technology at the smelter is paying off."

International interest

The monitoring of Clearwater Lake is believed to have created the longest record of the effect of air quality on water in the world, Gunn said, and that has brought international interest in the lake's recovery.

Scientists from Peru and Russia observed the field course last week at Clearwater Lake, along with students from several Ontario universities.

Alex Santiago Uriarte Ortiz

Alex Santiago Uriarte Ortiz or Lima, Peru, visited Sudbury last week to learn more about the recovery from mining degredation. (Megan Thomas/CBC)

"[We hope] to learn a lot from Sudbury, what has happened here, the different experiences. [We] have a lot of problems in Peru related to mining and the environment," said Alex Santiago Uriarte Ortiz of Lima, Peru, said through a translator.

Gunn said he hopes monitoring of Clearwater Lake will continue even thought it has recovered, because the lake could help scientists better understand everything from the effects of road salt on the environment to climate change.