Rain and snow spell relief for Great Lakes

By Jonathan Spicer

TORONTO (Reuters) - Twice as much autumn rain and early winter ice helped Lake Superior, the biggest of North America's Great Lakes, bounce back from record low water levels reached last year.

The deep, cold lake on the Canada-U.S. border -- the largest freshwater body of water in the world by surface area -- rose about 31 cm (1 foot) in seven months, with half of that in April alone as the spring thaw melted heavy winter snowfall that arrived late in the season.

The turnaround in the uppermost of the Great Lakes could literally trickle down to its four lower cousins, spelling relief for shippers who use the major waterway and residents concerned over shallow channels and receding shorelines.

"The spring runoff was much anticipated, and conditions have appeared to return to normal," said Melissa Kropfreiter, a hydraulic engineer with the U.S. Army Corps of Engineers, which studies the water levels.

In the last 30 years, precipitation has decreased while evaporation has increased. That led to higher water temperatures and, in recent years, lower water levels in the three upper Great Lakes -- Superior, Huron and Michigan.

With the inland waterway a key route for shipping bulk commodities like grain, steel or coal, the low water forced ships to lighten their loads. Last summer, some of the shallows and riverbeds used by fish for spawning dried up.

But that pattern, seen by many as a mark of global climate change, appears to have reversed at least over the last half year.

HURON, MICHIGAN ALSO RISING