Lake Levels

The Dynamic Great Lakes

Water levels in the Great Lakes have always been highly variable. They fluctuate over time in response to wind, storms, precipitation and evaporation from the lakes’ surfaces and runoff from tributaries.

Seasonal variation occurs every year as the lakes rise an average of 12-18 inches from winter to early summer. Long-term fluctuations lasting many years, decades or longer are visible in the historical record (US Army Corps of Engineers). Each Great Lake is unique in how it responds to the factors that influence lake levels: it depends on the size and composition of the lake’s watershed, total volume of the lake basin and other characteristics. The lakes also influence each other’s levels, as they are all interconnected.

One common concern when considering varying lake levels is how climate change could affect the Great Lakes and coastal communities. Michigan Sea Grant created a suite fact sheets, hosted workshops and developed educational lessons to address what residents, communities and leaders need to know about changing lake levels.

Fluctuating Lake Levels

With more than 3,200 miles of Great Lakes shoreline, lake levels have a huge impact on Michigan’s coastal communities and economies. Lake levels affect coastal properties and infrastructure, plant and wildlife habitat, shipping, recreation and manufacturing.

When levels fluctuate much above or below the long-term average, the impacts can be significant, especially in highly developed areas where infrastructure was not designed to withstand changing levels. Michigan Sea Grant is working on coastal community planning initiatives to address the impact of fluctuating lake levels on the boating industry and other coastal-dependent businesses. See: Vibrant Waterfront Communities

Ups and Downs

Whether future climate matches the predictions of scientists, consider this: it doesn’t matter. The reality is that weather, climate and lake levels will continue to be variable. Instead of reacting to the highs and lows in temperature, precipitation and lake levels, it is important for coastal communities to expect and prepare for these ups and downs.

Plan for Highs and Lowssandbags
In Michigan, the weather changes frequently and sometimes drastically. Water levels also naturally fluctuate daily, seasonally and over decades. The changing climate adds yet another layer of variability.

Scientists expect trend of extremes to continue
In recent decades, we have experienced more severe and frequent extreme events, like major storms and heat waves. Regardless, climate and lake levels will continue to change. Building coastal infrastructure expecting low levels to persist indefinitely may leave communities unprepared for when levels rise again. A best practice is to prepare for a range of outcomes.

See: Preparing for Extremes: The Dynamic Great Lakes (PDF)


Low Lake Levels

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