Great Lakes Water Levels: Adapting to Uncertainty

As a coastal business owner for more than 40 years, marina owner Dave Irish has seen the highs and lows of fluctuating Great Lakes water levels.

With a marina in Harbor Springs and two in Charlevoix, he’s learned to adapt to variability.

“We’ve seen the water go from very high to very low,” says Irish, who opened the Irish Boat Shop in 1961. “It has a significant impact on business. With three marinas, we’re about as exposed to lake levels as you can get.”

Irish and his staff monitor daily water level charts and make changes when necessary. Adaptations include installing floating docks to accommodate variability, and dredging to maintain a required water depth. While expensive and often time-consuming, he says, as business owners, “our job is to adapt.”

But Irish wears a different hat as part of a public interest advisory group for a comprehensive study examining causes behind low water levels. In this role, Irish says, it’s the future of the lakes that’s important: “Our job is to understand what’s going on.”

Current water level charts show that while Lakes Michigan and Huron are above last year’s levels at this time, they are still well below the long-term average. Lake Superior, which hit an historic low in October 2007, is higher this year but still below the long-term average. See: Current Great Lakes Water Levels

Great Lakes water levels fluctuate throughout the year with water levels generally highest during summer. Over time, however, the highs and lows can be dramatic, explains Michigan Sea Grant’s Chuck Pistis.

“We know from the historic record that the lakes rise and fall in cycles and can fluctuate considerably. We’ve seen them go from record lows in 1964 to record highs in 1986. The difference between the all time low and high is more than six feet on Lake Michigan.”

Much of Michigan’s coastal infrastructure was built during a prolonged period of high water, Pistis adds, making it difficult to adjust to the other extreme. See: Historic Water Levels

The Great Lakes are part of a dynamic system with many influences. Some of the many factors affecting lake levels include both human impacts and natural processes.

Among the human impacts include several structural diversions or compensating works. A five-year study funded by the International Joint Commission is examining whether the regulation of Lake Superior outflows can be improved to address the evolving needs of users on lakes Superior, Huron, Michigan and Erie. The study is also investigating physical changes in the St. Clair River potentially due to activities such as dredging that may be affecting water levels and flows. See: International Upper Great Lakes Study

Among the natural processes that affect lake levels, the primary driving forces are precipitation and evaporation.
See: GLERL Great Lakes Water Levels fact sheet

The regional climate plays a role in influencing the amount of precipitation that falls into the lakes and their tributaries every year in the form of rain and snow. Hemispheric climate patterns such as La Nina can also bring moisture from outside the region. This happened during the winter of 2007-2008 in which parts of southern lower Michigan experienced record snowfall. See: National Weather Service (PDF) | La Niña and the Great Lakes Region

Over the long term, however, some scientists predict the region may grow drier. They suggest that increases in rain or snow may be unable to compensate for the drying effects of increased evaporation and transpiration in a warmer climate. See: Climate Change Impacts on the Great Lakes region

According to the National Oceanic and Atmospheric Administration, the average global land temperature for March 2008 was the warmest on record. Ocean surface temperatures were the 13th warmest. See: NOAA

Similarly, higher evaporation draws water from the Great Lakes, which also causes levels to decline. In recent years, the rate of evaporation has increased as the duration of ice cover on the lakes has decreased. See: Climate Change Impacts on the Great Lakes region

For coastal business owners like Dave Irish, adapting to short-term water level fluctuations is part of life. But, he adds, it’s the long-term future of the lakes that’s most important.

“As homeowners and concerned citizens, there’s significant concern over the larger questions of climate change and permanent systemic changes,” he says. “We just don’t know how it will all play out.”

Additional Links

• Irish Boat Shop / Michigan Clean Marina Program
• MSU climate change conference presentations
  

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