Six months ago, water levels in Lake Huron were at their lowest point since measurements began in 1918.

Thanks to melting snow flowing down from northern Ontario and a rainy spring, a bounce-back has begun.

“In April, we had a significant increase – about 24 centimetres, and it’s been going up since then,” says Geoff Peach of the Lake Huron Centre for Coastal Conservation.

But despite this year’s rise – almost 50 centimetres all told – levels remain well below their historical averages.

That might not be significant to people lounging on beaches or walking on boardwalks, but for boaters, especially the large freight ships for which the Great Lakes are a major route, anything lower carries significant risk.

“Unless it was dredged out, you weren’t going to get a boat in or out,” says Fred Ramsay, the Bayfield Harbour harbourmaster.

“I don’t think a lot of people realize what the Great Lakes really are, how much of an impact it makes on southwestern Ontario.”

It all comes down to a battle between precipitation and evaporation.

In a dry summer like the summer of 2012, evaporation wins and water levels plummet, but a precipitation-heavy summer like 2013 has water levels on the rise.

A proposal to place adjustable weirs on the bottom of the St. Clair River has been suggested, but Peach doubts its cost-effectiveness.

“They’re talking about spending $200 million to put these weirs in. The ultimate effect of that would be to raise levels about 10 to 15 centimetres,” he says.

“That’s a lot of money to be raising levels a fairly modest amount.”