When Hal Wilson moved to Baileys Harbor in 2001, he could walk across a "bone-dry causeway" to reach Cana Island, a favorite tourist spot topped with a historic lighthouse.

Several years ago, as Lake Michigan's waters rose, the Door County Maritime Museum, which owns and operates Cana Island, added a tractor that pulled a trailer for visitors to reach the lighthouse without getting their feet wet. This summer, water often covered the causeway; it was impassible even for the tractor for 30 days this summer.

Wilson expects next year to be as bad, or worse.

"We’re anticipating high levels next year so we’re upgrading our equipment. But if it keeps going the way it is, we might have the same problem next year," he said.

Like the causeway, shorelines around Lake Michigan and the Great Lakes have changed dramatically as lake levels steadily rose from record lows hit just six years ago. This year, Lake Michigan rose an additional 15 inches, according to the National Oceanic and Atmospheric Administration, matching the record high set in 1986.

In Door County, homeowners reported eroded shorelines, property damage and fish washing up in yards. Beaches shrank, docks were submerged and roads were at times underwater.

Locals buffeted by the change are wondering if they should expect these levels in coming years, and whether it's related to a changing global climate.

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Scientists' answer: The Great Lakes are a complicated system affected by precipitation, winter ice cover, evaporation and other factors, but there's no clear evidence that climate change has a direct effect on how high the water is.

And the lakes are cyclical: Experts expect the cycle to bring water levels down in coming years.

However, scientists also say people should be prepared for anything as a changing climate brings more extreme weather to the region.

Lake levels are expected to fluctuate more frequently than people are accustomed to, according to Evan Murdock, a water resources engineer at MARS-EOR, a Madison-based engineering firm. Extreme highs and lows for Lake Michigan are not a new normal, he said, but could happen again, and so can any height between.

No easy answers on climate

Wisconsin has experienced warmer temperatures, but is also starting to see an increase in total annual precipitation, according to Jack Williams, a University of Wisconsin-Madison geography professor and climate change expert.

One theory, Williams said, is a warmer atmosphere holds more water vapor and is more energetic, and the energy releases bigger storms.

This year, Green Bay has already set a new record for total annual precipitation, including rain, snow and sleet. The previous record was set last year. Other parts of the state also are close to setting new annual records.

So much rain has fallen on northeastern Wisconsin that the Army Corps of Engineers last month took the unusual step of increasing flow from the dams on the Lower Fox River to prevent flooding and property damage on Lake Winnebago and the Upper Fox and Wolf rivers. All of that water flows into the bay of Green Bay.

Water levels in Lake Michigan can be affected by heavy precipitation because the Great Lakes have little area into which to drain, and that increases the possibility of a higher frequency of abnormally high water levels during cycles of extremely wet weather, Williams said.

"We tend to see a lot of variability in the (Great Lakes region) because they have such a small watershed and are sensitive to rainfall falling on them," he said.

Lakes levels in the Great Lakes have always been cyclical, rising and falling in a seven-year rotation, said Sarah Szabo, water regulation and zoning specialist with the state DNR. Lake levels can fluctuate up to 6 feet over 30 years. But scientists do not take the current extreme high levels as "evidence of a longer-term trend," according to NOAA.

Brent Lofgren, a physical scientist with NOAA's Great Lakes Environmental Research Laboratory, said he has "difficulty with the viewpoint" that these extremes prove a link between climate change and lake levels.

When water was extremely low in 2013, scientists and media reported lakes would drop up to 6 feet in coming years — clearly, those predictions come with uncertainty.

Lofgren's research shows very slight drops in average Great Lakes levels over a century. He thinks climate change has some influence on lake levels, but there's too much unknown to accurately define the connection.

"It's dangerous to look at something that has happened and assume it’s a result of climate change," he said. "Scientists want to understand reason and process that would link climate change or greenhouse gases to lake levels and it's not straightforward."

While scientists shrug at questions related to future levels, locals have to prepare for effects that lake levels have on the recreation and industry Door County's known for.

Residents brace for more extremes

Infrastructure on the lakes — things like docks, seawalls and shipping lanes — are built to handle a range of lake levels, but are challenged by extremes, said Jay Austin, a professor at the University of Minnesota-Duluth's Large Lakes Observatory.

If the water level is too low, a ship can't carry as much cargo. Too high and docks and seawalls submerge and breakwalls can become less effective. These structures are built with typical changes in lake height in mind, but those structures can be stressed by highs and lows that are starting to be "pretty extreme," Austin said.

"Water levels in the Great Lakes are a really hard thing to predict in the long term," Austin said. "We’ve designed the built infrastructure of the Great Lakes with an assumption that a variability we observe is within some prescribed range. We’re seeing they're getting out of that designed range."

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A lifelong Fish Creek resident, Harbor Commission Chairman Dave Harris remembers the last time the water was this high in 1986.

Harris also worked with the harbor in 2013, when Lake Michigan reached record lows and the commission dredged channels to the fuel dock at Fish Creek Harbor and into the marina on Chambers Island. Dredging cost the town $30,000 that year. This summer, water came within a couple of inches of completely covering the fuel dock, so the commission added extension pipes from fuel tanks to the harbor's parking lot, where the pipes are surrounded by cement barriers.

In late July the harbor commission added 8 inches of travel to their floating docks to ensure they remain above the water. He expects water to cover the Fish Creek Town Dock later this fall and is considering raising all the docks before temperatures drop.

"Every marina's had to figure out how to deal with this high water," Harris said. "We still have high water now; generally it will surge in the fall. ... It's just very hard to predict and you have to be flexible to deal with it."

The secret to flexibility, Murdock said, is to "focus on resiliency in design." Communities must look into their crystal balls to anticipate any possible damage, and come up with methods to keep land and buildings safe, or at least be prepared for cleanup.

Unpredictable water levels aren't all bad.

Higher lake levels also benefit peninsula boaters and anglers, offering increased access to the water and more options for deeper draft vessels.

According to the U.S. Army Corps of Engineers predictions, water levels will likely start higher in 2020 than they were in the first months of 2019. However, the corps' Detroit District Chief of Watershed Hydrology Keith Kompoltowicz said next year's peak level will be dependent on the climate conditions in winter and spring.

He said people in the region can expect wet conditions over the next six months, which leads the agency to believe high water levels will continue in 2020.

Contact Sammy Gibbons at (920) 431-8396 or sgibbons@gannett.com. Follow her on Twitter at @sammykgibbons or Facebook at www.facebook.com/ReporterSammyGibbons.