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The Badger on Big Green Lake: Green County

Stephanie Prellwitz MS’13 and the Green Lake Association are trying to create a model for keeping Wisconsin’s lakes clean.

Stephanie Prellwitz

With an area of 7,346 acres and a depth of 237 feet, Big Green Lake lives up to its name. It’s a special lake, famous for its cold, clear water and its trophy lake trout.

But all is not well on Big Green Lake. In 2014, the Wisconsin Department of Natural Resources designated it as “impaired” because it had low levels of dissolved oxygen. An increase in phosphorus in the lake had caused algae blooms that ultimately pulled oxygen from its water.

“The listing as impaired was a real wake-up call for us,” said Stephanie Prellwitz MS’13, who earned her master’s degree in biological systems engineering from UW–Madison and is now the executive director of the Green Lake Association.

“Lake trout are a really important part of our history,” says Prellwitz. “The ability to support this cold-water fish makes the lake really unique.”

To find some solutions to the lake’s problems, Prellwitz and her lake association turned to the UW, forming a novel partnership with the Nelson Institute for Environmental Studies.

UW–Madison scientists are using Green Lake as a living laboratory.

“UW–Madison scientists are using Green Lake as a living laboratory,” says Prellwitz.

She and the UW–Madison researchers follow an important principle when examining the lake’s ecosystem.

“We must treat the disease and not the symptom,” says Prellwitz. “So, we worked upstream to find the problem at its source. If you want cleaner lakes, you have to think beyond the lake.”

Prellwitz and university scientists have concluded that wetlands are critical for filtering water that flows into the lake after comparing a healthy wetland with another that was degraded by an invasive species of carp. By studying these wetlands, scientists are learning more about what it takes to improve wetland health, which will ultimately lead to cleaner lake water.

“It’s an interdisciplinary challenge,” says Prellwitz. “Environmental problems are easy to figure out. The challenge is when you have to work with other people to solve them.”

With the help of the Nelson Institute at UW–Madison, Prellwitz is meeting that challenge.

“We’re trying to aim high — to create a framework for clean lakes throughout Wisconsin.”

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