If you’ve taken a tour with us this past season, you may have noticed a few “extra” buoys on the water. This is because our Lake Huron water levels are about 18″ lower than normal; this fall, they are actually edging closer to two feet lower! This is bad news for boaters.
Many customers ask us why this is happening, and the difficulty in answering lies in the fact that there are actually several things that influence our Great Lakes water levels.
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Here are some key factors contributing to lower water levels right now:
1. Reduced Precipitation and Runoff (Less Water In)
The most direct cause is often a period of drier-than-average conditions across the Great Lakes basin.
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Below-Average Precipitation: If the region has experienced several consecutive months, or even years, with less rainfall and snowfall than normal, there is simply less water entering the system.
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Reduced Runoff: Less precipitation means less water available to run off the land and flow into the lakes via rivers and streams. This significantly cuts the total “inflow” to the lakes.
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2. High Evaporation Rates (More Water Out)
This is often the major “invisible force” driving lake levels down, particularly on the upper lakes (Superior, Michigan, and Huron).
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Warm Water and Cold Air: Evaporation is maximized in the late fall and early winter when the lake water is still relatively warm from the summer, but the air above it has turned cold and dry. This creates a huge temperature difference, which is perfect for drawing moisture out of the lake surface.
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Lack of Ice Cover: A crucial factor in recent years is the trend of milder winters and reduced ice cover. When a Great Lake freezes over, that ice acts like a cap, essentially shutting down evaporation. When the lakes remain open and unfrozen during cold, windy periods, they lose enormous amounts of water to the atmosphere through evaporation, which accelerates the decline in water levels during the winter and early spring.
3. The Seasonal Cycle
It’s important to remember that the Great Lakes follow a natural, predictable annual cycle:
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Low Point: Levels typically reach their lowest point in the late winter or early spring (February/March). This is after months of the fall/winter decline driven by evaporation and reduced runoff.
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High Point: Levels typically peak in the summer (June/July) due to spring snowmelt and increased spring rainfall.
