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Speaker Explains Great Lakes Water Level Changes

A physical scientist with the National Oceanic and Atmospheric Administration told delegates at the recent “Is the Coast Clear” conference that there are three main drivers that affect water levels in the Great Lakes over a long period of time.

Doctor Andrew Gronewold says they are the precipitation that falls directly on the lake surface, the evaporation that draws water off of the lake surface, and then all of the runoff that comes into each of the lakes through rivers and streams.

But he also points out things like changes in the jet stream, changes in the continental-scale precipitation patterns, which are impacted by climate change, can impact how water variability changes over time, just as global temperatures can impact rates of evaporation.

Dr. Gronewold says it difficult pin down precise cycles because they do vary, but what has generally happened is as precipitation went up, so did water levels and when precipitation dropped, water levels did too. That changed in the late 1990’s when precipitation rates stayed high but water levels went down. It was one of the first times there was a departure from the previous normal pattern.

So the fact that we’re in a time period when precipitation and evaporation are at these extremes and are competing to dictate where the water levels go up and down is a new phenomenon relative to the previous hundred year record that we have.

Dr. Gronewold was one of the keynote speakers at the Lake Huron Centre for Coastal Conservation conference in Grand Bend.

National Oceanic and Atmospheric Administration Physical Scientist, Doctor Andrew Gronewold (photo by Bob Montgomery)