LUDINGTON, Mich. Great Lakes water levels are rebounding after a decade-long slump 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 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.
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.
A sudden, deep drop-off began in the late 1990s. It forced cargo ships to lighten their loads to avoid hitting bottom in harbors and channels. Some marina operators were unable to lease slips because the water was too shallow for boats to reach them. Dredging to deepen boat passageways released chemicals and other pollutants that had been buried for years under layers of sediment.
While some waterfront property owners rejoiced over wider beaches, others griped as vegetation sometimes unsightly and smelly sprang up.
Scientists attribute the rebound primarily to wetter, colder weather the past couple of years. But even if the lakes are entering another period of higher water, it does not alter a grim prognosis suggested by climate change computer modeling.
If the estimates prove accurate, global warming will cause the lakes to recede up to 3 feet this century, despite occasional bumps that could temporarily mask the long-term downward trend.
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.
Such predictions spark mixed reactions around the lakes.
Boaters at the municipal marina in the Lake Michigan town of Ludington can climb into their vessels now without using wooden ladders installed several years ago, when the low water made it hazardous to jump from dock to boat.
We re in a lot better shape this year, said Jim Christensen, the marina s assistant manager.
Farther up the Pere Marquette River, Ludington s outlet to the big lake, the water is deep enough for John Chippi to rent nearly all his 40 boat slips. But one is still carpeted with swamp grass that sprouted in the wet sand as the water faded.
Sometimes I wonder why I ever bought a marina, Chippi said with a bemused chuckle, gazing at the head-high vegetation.
The high water levels also are helping shipping companies that use the lakes. Low water during the past decade forced the haulers to lighten their loads of iron ore, coal and other goods, which meant less money.
Ships sacrifice 50 to 270 tons of cargo for every inch of water loss they must accommodate.
Water levels have risen some, but our problem isn t solved, said Glen Nekvasil, spokesman for the Cleveland-based Lake Carriers Association, which represents U.S.-flagged ships. His group says levels are still too shallow in some places and is pushing the government for more dredging.
The Great Lakes have yearly highs and lows. But 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-off that began in the late 1990s wasn t unexpected. But its suddenness and severity caught many off guard, especially after a period of unusually high levels.
Drought and warming temperatures aggravated the situation. Winter ice caps, crucial for limiting evaporation, formed in ever smaller areas.
Since fall 2007, shortly after Superior hit its all-time low, rain and snow have picked up and winters have been colder. The lakes had substantial ice cover during the winter of 2008-09, said Keith Kompoltowicz, a meteorologist with the Army Corps in Detroit.
At the end of June, Huron and Michigan which hydrologically are one lake because they are connected and have the same level were 10 inches higher than the previous year. Erie had risen 5 inches, while Superior was near the same level as a year earlier and Ontario was an inch lower.
Strikingly, both Ontario and Erie were 5 inches above their long-term average levels while Superior, Michigan and Huron had pulled to within 6 inches of theirs.
When levels were plummeting, some lakeside residents muttered darkly about secret deals to pipe water to the parched Sun Belt. Such suspicions are heard less frequently these days. But controversy persists.
A Canadian group representing homeowners on Lake Huron s Georgian Bay contends navigational dredging and mining have lowered Huron-Michigan by increasing outflow to Lake Erie. Members want structures placed in the river to stem the tide.
A study released in May by the International Joint Commission, a U.S.-Canadian advisory panel, disputed the need for that.
Jim Te Selle of Cedarburg, Wis., president of a Lake Michigan shoreline property owners group, is reluctant to tinker further with the lakes, even though they re already regulated to some extent by hydropower dams and locks.
He remembers the high-water days of the 1980s, when the lake lapped right to his front porch.
The truth is that we have no idea what the lakes are going to do, Te Selle said. It s better for Mother Nature to be left alone to do her thing.
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