GRAND RAPIDS, Mich. (WOOD) — Anybody who has been to Lake Michigan lately — or any of the Great Lakes, for that matter — has noticed how high the water level is. All of the Great Lakes are at or exceeding record highs.
But how did we get here? The record levels are reached not by just one factor but are rather the culmination of several coinciding with each other.
It’s amazing how much Great Lakes ice levels can fluctuate annually. Take 2015 to 2016 for instance. The difference is substantial. 2015 saw more than double the amount of ice of 2016.
But over the past six years, four were above the long-term average of 55.7%.
That’s important because the more ice that forms on the Great Lakes, the less water that can be evaporated from the surface. When dry, frigid, Arctic air masses arrive across the lakes, a substantial amount of water can evaporate. We see that process unfold many times during the winter in the form of “lake-effect” snow. But the process is broken down when ice is covering the water.
RAIN AND SNOW
Another important factor is how much precipitation falls across the Great Lakes basin.
The map below shows the precipitation anomaly the past four months across the Great Lakes. Blues and green colors represent above-average precipitation.
One thing that stands out is how nearly all of the Great Lakes basin has received above-average precipitation.
This is reflected at various shoreline cities. It doesn’t matter if it’s Muskegon; Green Bay, Wisconsin; Cleveland; or Buffalo, New York — they are all well above average in terms of precipitation. Some places, like Sault Ste. Marie, are nearly 10 inches above average for the year. Every station with the exception of Sault Ste. Marie, had above average precipitation in 2018.
All that excess water has to drain somewhere and ultimately, it’s to our massive lakes.
Of course, when you have all of this excess precipitation, a portion of it is absorbed by the soil. But just like a sponge that is already saturated, the soil can only hold so much water.
The soil moisture content is at near max capacity (95-99 percentile) from the Great Lakes through the Central Plains. So when additional rain falls, it cannot be efficiently absorbed by the soil. Therefore, it turns into direct runoff into adjacent streams and rivers. These are the same tributaries that ultimately flow into the Great Lakes.
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The longer daylight hours of spring and summer can really help evaporate water. As temperatures increase, so does the process of evaporation.
It has been a cool spring and start to summer, so that process has not been as efficient. Note the widespread cool that has dominated the Great Lakes the past four months.
One of the reasons it has been so cool is the limited sunshine. Every month this year has experienced below-average sunshine levels. May, for instance, was as much 20% below average, leading to the third cloudiest May on record. Less sun equals cooler temperatures and less evaporation.
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The warmest temperatures of the season wunill be arriving in the coming days, which will help a bit.
But at the same time, the wet pattern will remain.
As the heat competes with the additional rainfall, one thing seems certain: The high water levels will be with us well through the summer months.
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100 YEARS OF LAKE MICHIGAN LEVELS
The U.S. Army Corps of Engineers has recorded water level data on Lake Michigan since 1918. There was a period in the 1930s when levels were very low, and they were low again in the 1960s. They climbed back above average through the ’70s and ’80s, then dropped down again for an extended period between the late ’90s until around 2014.
The levels on Lake Michigan have been climbing back up ever since.
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In January 2013, water levels dropped lower than any time in recorded history. Water levels had been low for several years and there was minimal snowpack in the winter of 2011-2012. The summer of 2012 was very hot and dry. Because of that, there was a seasonal rise of only 4 inches on Lake Michigan in 2012. The normal seasonal rise is closer to 11 or 12 inches.
Rewind a few more years and a record high was set in October 1986. Water levels were high through the summer, and rainy conditions through the late summer and early fall pushed the levels over the edge. Muskegon had 13.55 inches of rainfall in September 1986 alone. Flooding and beach erosion was common and houses even crumbled into the lake along the shoreline.
Water levels on Lake Michigan have not broken the 1986 record this year, but it isn’t out of the question. Our water levels are forecast to stay high for at least the next six months.
Anyone familiar with the lakeshore will tell you that the change is constant on the Great Lakes. Water levels will be high again and they will be low again. We just have to prepare the best we can for all scenarios.