As Madison rethinks road salt, UW grad student explores its effects on a local lake

As Dane County reevaluates salting procedures on Madison roads, limnology researchers at the University of Wisconsin-Madison are studying how the region’s winter salt usage impacts local lakes. 

Elizabeth Emch is a second-year master’s student in limnology, the study of inland water. She works in the Hilary Dugan lab, where she has been studying salt concentrations in Lake Wingra, the small lake bordering the UW-Madison arboretum.

“In any places that use road salt, it takes a long time for chloride itself to flush out,” Emch said. “So the number one thing that we try to emphasize is people changing their inputs, because we can't really change the outflow.”

Of all Madison’s lakes, Emch said Lake Wingra has the highest concentration of chloride. She said this is due to many reasons, but she pointed to two in particular: its proximity to urban land and roads and its relatively small size. 

“Wingra has the highest amount of chloride and since it’s not surrounded by any agricultural land… it's just us humans,” Emch said. “It's a really good model.”

According to Emch, salt can have several negative effects on the ecosystem.

“Invasive species usually have more tolerance to these types of contaminants, nutrients and salt. So they start to overgrow and overpower more than the native species,” Emch said. “There was a study in Ohio where they measured fish length and the fish were growing smaller because of salt in the freshwater.”

Salt impacts stretch beyond Madison’s species and lakes. According to the City of Madison, salt infiltration has been observed at five wells. 

Madison Water Utility estimates water pumped from the well will exceed the taste threshold of 250 mg/L within the next 17 years, the website says.

City data indicates the sodium level at well 14 is currently at 45 mg/L. Drinking two liters of this water is equivalent to the sodium levels in one piece of bread, according to the city. Once salt infiltration has occurred, it is very difficult to remove salt from the ground and drinking water.

“I saw a quote from a woman about how limnologists are more interested in protecting the lakes than protecting the roads,” Emch said. “We want to make the roads safe for people, but it's not two separate things. We're keeping the lakes fresh and the bodies of water fresh so we can continue living and making sure our habitats are protected.”

Emch added that it was important to strike a balance between accessibility and safety while reducing salt usage. Sanding, for instance, can be used to reduce traction in snow and ice, and brine — when applied correctly at certain temperatures — can be even more effective than road salt.

“We definitely understand how people that have children need to roll their children in strollers, or that some folks need to use wheelchairs,” Emch continued. “[We’re] just trying to find that middle area of how to reduce salt usage.”

Emch recommended sweeping excess salt and reusing it as one example of utilizing salt more efficiently.

Although Emch does not currently research Lake Mendota and UW-Madison’s salt policy, she said her research on Lake Wingra could help model effective policies for other regional lakes, such as Lake Mendota and Lake Monona. 

Apart from research, Emch volunteers and partners with environmental agencies such as Wisconsin Salt Wise. The organization is currently advocating for the passing of Assembly Bill 61, which would reduce liabilities for companies who have completed a training process on methods to reduce salt usage.

The Clean Lakes Alliance is hosting its annual Frozen Assets festival on Lake Mendota Feb. 3-4. Emch will be tabling at the event to discuss her research on Lake Wingra and the negative impacts of road salt on local lakes.

“The majority of people do know that salting is bad, but it's like, what should we do?” Emch said. “And so I've just been approaching it like, here's our lake we love dearly. Here's what we can do.”

---