Researchers Investigate Longterm Drop In Northern Wisconsin Lake Water Levels

Mercury Levels On The Rise Even As Lakes Get Smaller

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Above, DNR researcher Carl Watras. Photo: Glen Moberg/WPR News.

Researchers are trying to determine whether climate change is linked to a 12-year drop in water levels in northern Wisconsin lakes.

Department of Natural Resources research scientist Carl Watras said he’s troubled by what’s happening to many of the 7,000 lakes that surround the Trout Lake research station.

“It’s not good news,” said Watras. “Over the last 12 years, as the lake levels dropped, the forest began to move in, the distance between the house and the lake began to increase, and docks had to be moved.”

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Watras says normally, the lakes go through a 13-year boom and bust cycle. It’s been all “bust” since 1998.

“We go from high water to high water roughly every 13 years, or have for most of the last century,” said Watras. “Starting in about 1998, that changed. It’s been a much longer decline than we’ve seen in the past.”

Watras led a groundbreaking experiment on acid rain and mercury pollution at nearby Little Rock Lake, research that led to stricter controls on coal fired power plants. But despite cleaner air, mercury levels are rising again as the lakes get smaller.

“Acid rain and mercury rain have continued to decline, but starting in ‘98, mercury contamination increased, said Watras. And the timing is just about identical with the time of the change in the lake levels.”

Watras thinks the shrinking lakes have exposed mercury contaminated sediment. His team is monitoring water levels with citizen volunteers at more than 40 lakes, to see if climate change is responsible.

“It’s a climatic effect,” he said. “Whether it’s what we would put under the umbrella of climate change remains to be seen.”

Carl Watras says lake levels have risen at least temporarily this year because of heavy snow and rain.