TRAVERSE CITY -- Great Lakes water levels are on the rebound after receding for a decade, and local boater Chet Swanson can see the difference.
"I notice it on the shorelines. You can see the water is up on the permanent docks," said Swanson, a boater from Traverse City who keeps his vessel at Duncan L. Clinch Marina.
Swanson lived along the shoreline on Old Mission Peninsula during the 1980s, when water levels crested in his backyard. It's been decreasing every year since then, until now.
"You can get in places you couldn't when the water was so low," said boater Jan Carda, of Traverse City.
Great Lakes water levels fell in recent years, a trend that hammered the maritime industry and even fed conspiracy theories about plots to drain the inland seas that make up nearly one-fifth of the world's fresh surface water.
The three biggest lakes -- Superior, Huron and Michigan -- have risen steadily since fall 2007, when for a couple of months Superior's levels were the lowest on record and the others nearly so. Erie, shallowest of the lakes, actually exceeded its long-term average in June. So did Lake Ontario, although its level is determined more by artificial structures than nature.
"It's important to remember lake levels naturally change over time. We appear to be on the natural upswing. It's part of nature," said Andy Knott, executive director at the Watershed Center Grand Traverse Bay. "It will be interesting to see how long this upswing lasts and how high it will get. Only time will tell."
The lakes follow cycles, rising and falling over time. Scientists say it's a natural process with environmental benefits, such as replenishing coastal wetlands. But extreme ups or downs can wreak havoc for people. During the mid-1980s, levels got so high that houses, businesses and even sections of roads were swept away along Lake Michigan's southeastern shoreline.
Then a sudden, deep drop-off began in the late 1990s. Cargo ships were forced to substantially lighten their loads. Marina operators were unable to lease slips. Dredging to deepen boat passageways released pollutants that had been buried for years under layers of sediment.
Operators of public marinas and boat launches that dot the Lake Michigan shoreline throughout northern Michigan said the higher water levels are welcome both by boaters and municipalities that have to undertake costly dredging work to keep them navigable.
"The last two years we've had no problems getting in and out of the marina," said Wally Delamater, the village manager for Suttons Bay in Leelanau County. "And we haven't had to dredge."
Delamater said his marina staff estimates the water level there is about 18 inches higher than two years ago. It's also improved conditions at the village's North Park boat launch, where larger watercraft had problems in recent years.
"Now, there's sufficient water to get in and out of there," he said.
While some waterfront property owners rejoiced over wider beaches with the lower water levels, others griped as vegetation -- sometimes unsightly and smelly -- sprang up. That's changing as the water level rises.
"It will bring back some of the native habitat we haven't seen in 20 years," Knott said.
Scientists attribute the rebound primarily to wetter, colder weather the past couple of years. But if grim computer modeling proves accurate, global warming will cause the lakes to recede up to 3 feet this century
"Climate projections say the lakes will go up and down around a decreasing average," said Don Scavia, director of the University of Michigan's Graham Environmental Sustainability Institute. "The lows will be lower than in the past and the highs will be lower than in the past."
Records extending to the mid-1800s document a series of larger rises and dips at roughly 30-year intervals, said Craig Stow, a scientist with the National Oceanic and Atmospheric Administration's Great Lakes Environmental Research Laboratory in Ann Arbor.
So the drop in the 1990s wasn't unexpected, but its suddenness and severity caught many off guard. Drought and warming temperatures didn't help as winter ice caps, crucial for limiting evaporation, formed in ever smaller areas.
Since fall 2007, rain and snow have picked up and winters have been colder. The lakes had substantial ice cover during the 2008-09 winter, meteorologists say.
At the end of June, Huron and Michigan -- which hydrologically are one lake -- were 10 inches higher than the previous year. Erie had risen 5 inches, Superior was near the same level and Ontario was an inch lower. Ontario and Erie were 5 inches above their long-term averages, while the others were within 6 inches of theirs.
The Associated Press and Business Editor Bill O'Brien contributed to this article.
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