On a chilly February day in Madison, Wisconsin, more than 8,000 people venture onto frozen Lake Mendota. Kids toast marshmallows and warm their hands over fires; people try curling, they skate, they slide, they fall on their butts — they have a great time. Kites brighten up the frozen landscape. Skydivers jump from planes and land on the lake’s glossy surface. This is the annual Frozen Assets Festival, a citywide party and a fundraiser for Clean Lakes Alliance.

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people walking on a frozen lake

“The neat thing about Madison is that we have these five lakes,” said James Tye, founder and executive director of Clean Lakes Alliance. “And all spring, all summer, all fall, people are fishing and they’re kayaking and they’re doing all these wonderful things on the lakes. But in the winter, they’re frozen. And our lakes, to our community, are our biggest assets. So doing a play on words, they are truly our frozen assets in the winter.” When Mendota, the biggest lake, is frozen, it can turn into the city’s largest park with just a little imagination.

Related: 5 sustainable activities to make the most of a winter wonderland

person in boat monitoring lake pollution

A chain of lakes

The 62-mile long Yahara River connects Madison’s five lakes. Mendota is the first and largest lake in the Yahara chain. The others are Monona, Waubesa, Kegonsa and Wingra.

Before western explorers came to Wisconsin, the Ho-Chunk Nation inhabited southern Wisconsin, including present-day Madison. Later, white settlers developed Madison, eventually moving the state capital here. The lakes have always been an important part of the area’s history. “We’re a coastal city in landlocked middle America,” said Adam Sodersten, marketing and communications director of Clean Lakes Alliance. “Without the lakes, we’re Lincoln, Nebraska. We’re a capital in a Midwestern city. But because we have these large urban gems, it really makes Madison stand out.”

For most Madison residents these days, the lakes mean recreation. The five lakes have a combined total of 24 miles of publicly owned shoreline, said Sodersten. “So they’re not inaccessible. They’re not just built up by people who can afford to live on the lakes. There’s public spaces, there’s the university, there are state parks, county parks. They’re truly the people’s lakes.”

The lakes also serve as an important recruiting tool for large businesses headquartered in Madison. To attract the best talent — especially millennials focused on work/life balance — companies have to demonstrate a high quality of life. “So the businesses here have really recognized that when people fly into Madison, if they’re flying into Dane County, they can’t fly over green and unusable lakes,” Sodersten said.

people on lake shoreline cleaning up waste and debris

Dangers to Madison’s lakes

James Tye founded Clean Lakes Alliance in 2010 to protect the lakes he loves. “I’m actually a townie,” he said. “I’m actually from Madison, and was fortunate that my dad taught me how to swim and fish, canoe and kayak, waterski and sail on the Madison lakes. So at a very young age, I got that water connection.”

Despite the residents’ love of lakes, they didn’t know how to best take care of them. Part of the trouble was century-old infrastructure that was built long before today’s current best practices for lake management. Storm sewers channel water straight into the lakes. One of the lakes’ biggest enemies? Leaves. Especially leaves in streets. “So when a leaf is in the street, the storm water runs through it like a teabag,” Sodersten explained. That phosphorus-rich storm water flows into the lake, fueling cyanobacteria bloom. Commonly known as blue-green algae, cyanobacteria can be toxic enough to require officials to close beaches.

Because changing the infrastructure would be extremely difficult and costly, Clean Lakes Alliance focuses on what people can do to protect the lakes. Clean Lakes Alliance works with other cities and municipalities around the watershed to coordinate leaf management efforts. Instead of raking leaves into the streets, Clean Lakes Alliance suggests individuals pile leaves on their own grass or onto the narrow strip of grass between the sidewalk and the street. If homeowners keep storm water on their property by building a rain garden or collecting it in rain barrels, the lakes would appreciate it.

But in addition to Madison’s urban area, the watershed also serves a very large rural area. “We’re the dairy state,” Tye said, emphasizing the productivity of Dane County’s cows. Clean Lakes Alliance partners with farmers to impart ways to reduce erosion and runoff and to improve manure management. One simple example is installing harvestable buffer strips at least 30 feet wide between fields and the nearest stream or shore ditch. Clean Lakes Alliance also helped purchase a manure injector machine that local farmers can rent. Instead of spreading manure on a frozen field for winter — bad for runoff — the machine shoots the manure 6 inches into the ground, putting the nutrients right at the roots of plants where farmers need them.

volunteers in orange vests standing in a group and smiling

Lake cleanup and monitoring

Clean Lakes Alliance volunteers have the opportunity to take on many tasks. Volunteer jobs include office work, picking up trash, raking beaches, getting leaves off the streets in fall, water monitoring, partnering with local parks to remove invasive species and stamping storm water drains to warn people that the water goes directly to the lake.

“More companies are having their employees do teambuilding exercises by doing volunteer days,” Tye said. “Like from Lands’ End alone, they’ll bring out 100 to 160 people on a volunteer day. They’re working at a park called Pheasant Branch Conservancy. And they’re doing the major work to restore the creek that goes right into Lake Mendota.”

The lake monitoring program is especially useful to locals planning a day of kayaking or swimming in the lakes. Clean Lakes Alliance partners with the city and county health departments and the University of Wisconsin to gauge lake clarity. From Memorial Day weekend through mid-November, 70 citizen monitors trained by Clean Lakes Alliance check the water quality at local beaches and post their findings to Lakeforecast.org.

“It tells people what the clarity of the lake is, what beaches are open, what beaches are closed,” Tye said. The citizen monitors provide the fine-tuned data so folks can plan their recreational activities. “The beach might be open and there might be one foot of clarity. But maybe a beach on the other side of the lake has three feet of clarity.”

Clean Lakes Alliance hopes that its campaign to educate greater Madison will normalize everyday actions people can take to protect the lakes. “It’s sort of like recycling,” Tye said. “In Madison in the ‘70s, we started tying up newspapers and putting them out in the street. Now you’ve got two trashcans built into your kitchen that you open up a door and there’s recycling and non-recycling.” He hopes that people will think about the lakes when building parking lots, designing their own backyards and making decisions like adding rain barrels for water reuse. “One of those probably doesn’t make a difference,” Tye said. “But when you get 50,000 houses or 100,000 homes, you really start making an impact.”

+ Clean Lakes Alliance

Images via Teresa Bergen / Inhabitat and Clean Lakes Alliance