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Rising chloride levels in Lake Julia spur action by Lake Association members to reduce salt use in the area

Katie Thorsen

A thick layer of ice and snow currently covers the surface of Lake Julia in Oneida County.

Sue Thome can tell you a lot about the water beneath that surface.

“Clarity of the lake, then you track temperature, gradience of the lake. We track chlorophyll which is the amount of algae in the lake,” said Sue.

She took over testing water quality for the Lake Association shortly after she and her husband Bob bought a house on the lake nearly 10 years ago.

“I’ve never lived on a lake before. This was brand new. I was really excited. I need to learn about the plants and what’s growing here, and what’s the lake all about. I was excited to do stuff on the lake. I’m a scientist, so this is right up my alley,” said Sue.

All the information she collects on water clarity, chlorophyll, and phosphorus gets uploaded to the Wisconsin DNR’s Surface Water Integrated Monitoring System or SWIMS.

Data for Lake Julia goes back as far as 1976 with consistent, yearly testing starting in 1995.

It’s been in just the last five years that Sue added another item to her checklist: chloride levels, something that’s not commonly tested on Northwoods lakes.

Date SampledResults (mg/L)
May 201831.2
August 201832.2
May 201932.7
August 201935.5
June 202034.3
April 202136.6
May 202237.8

The above chart shows chloride test results from Lake Julia.

“And we found, since that initial sampling of around 30 mg/L, every year it’s gone up. It was concerning,” said Sue.

Of the couple dozen or so lakes in Oneida County that test for Chloride, Sue says Lake Julia has the highest levels. But it’s far from alone in seeing rising chloride levels in fresh water.

A sign at the public boat landing on Lake Julia. It's one of the areas the Lake Association tested for elevated levels of chloride last summer.
Katie Thoresen
A sign at the public boat landing on Lake Julia. It's one of the areas the Lake Association tested for elevated levels of chloride last summer.

That salt has been making its way into lakes in southern Wisconsin for decades.

The City of Madison says the chloride levels in Lake Mendota have been increasing by about one milligram per liter a year since 1962.

The Milwaukee Journal Sentinel recently reported a long-term monitoring site on the Mississippi River south of La Crosse showing levels of chloride have increased 66% since the early 1980s.

And researchers are finding that Sue is right to be concerned about the rising chloride levels.

Effects of chloride in lakes

“Salt is a pollutant in our freshwater. It’s a permanent pollutant in that it doesn’t break down. It’s there until the water flushes out of the system,” said Allison Madison, the program manager for Wisconsin Salt Wise. It’s a coalition of organizations in the state working together to reduce salt pollution in lakes, streams, and drinking water. “In addition to building up in our water salt levels are also building up in our soils and in the groundwater that re-charges our lakes and streams.”

She pointed to several recent studies that show how elevated levels of chloride are impacting some of the smallest organisms found in lakes.

“Scientists are seeing once we get up to 50 mg/L, it’s causing declines in the populations of more sensitive macroinvertebrates and zooplankton,” said Madison. “People don’t go around talking about zooplankton every day, but they’re really, really important in our aquatic ecosystem food chains. These are the things that fish eat. If we have less food for the fish, it means we’re going to have less fish.”

The levels being found in Lake Julia are still about 10 mg/L below the 50 mg/L mark.

But Sue Thome doesn’t want to wait to see if the lake will hit that mark.

“I don’t want to find out honestly. Cause that would mean the death of the lake,” said Sue. “The more we can try to prevent the salt from getting into the lake, the better off we are.”

Possible solutions

Sue and her husband Bob started looking at possible sources for the chloride. They started testing the lake water near different potential sources in July.

These are the test results from the five locations they tested:

  • Timber Lodge Boat Landing: 40.4 mg/L chloride
  • Crescent School Culvert: 39.5 mg/L chloride
  • Echo Lane Keyhole: 39.6 mg/L chloride
  • Nicolet College Theatre: 41.0 mg/L chloride
  • Nicolet College parking 39.7 mg/L chloride

Bob gathered representatives from Crescent Elementary School, Nicolet College, and The Town of Crescent along with people from the Wisconsin DNR, Oneida County Land and Water Conservation, and the Department of Agriculture, Trade, and Consumer Protection.

“We had a number of people that were cooperating, trying to see if we could solve the problem,” said Bob.

Terry Rutlin is the public information officer for Nicolet College. He says Nicolet has long been a steward of the environment, including his own work with the Lake Julia Association in the early 2000s

“Chloride is definitely a concern for us. The college wants sound environmental stewardship of the Lake Julia area. It’s definitely something to monitor. I’m glad we’re getting some numbers on this,” said Rutlin.

Rutlin says the college does try to keep its salt use to a minimum and will continue to do so, but it also has to keep safety in mind.

A photo Bob Thome took in November 2021 after a large rain event. He says water from the new parking lot at Crescent Elementary School is feeding into a ditch that drains into Lake Julia. The fear is that come spring that runoff will also be filled with salt used to clear ice.
Katie Thoresen
A photo Bob Thome took in November 2021 after a large rain event. He says water from the new parking lot at Crescent Elementary School is feeding into a ditch that drains into Lake Julia. The fear is that come spring that runoff will also be filled with salt used to clear ice.

“It’s a real balancing act between public safety and environmental stewardship. From the public safety aspect, slips and falls are a big deal. People get hurt when they slip and fall on the ice,” said Rutlin.

Bob Thome recognizes and understands that.

“You don’t want somebody falling, a little kid falling down in a parking lot or getting hit by hard when somebody can’t stop in the parking lot. There’s a balance there. I think the group has come up with a decent solution,” said Bob.

He says the solutions include the schools trying to reduce their salt use. The stormwater runoff from Crescent Elementary’s parking lot is also being looked at since it currently feeds into a drainage that flows into Lake Julia.

Though that’s difficult also since redirecting the water or creating a retention pond on the property could lead to salt saturating the groundwater which could also eventually end up in the lake.

“Months and months after we’ve put salt down, the concentrations continue to remain high because salt is making its way from the soils and the groundwater into those lakes and streams,” said Madison with Wisconsin Saltwise.

Madison says highway departments have been able to reduce salt use by laying brine down on roadways ahead of storms.

“If you put it down before the storm, it’s kind of like putting cooking spray down on your skillet before you put the food on. Spatula comes, and food comes right off. You don’t create that bond between the snow and the pavement. It’s so much easier. If you don’t do that it’s just more work it ends up being, using more salt afterward,” she said.

Madison also recommends clearing as much of the snow as possible manually either with a shovel, snow blower, plow, or even a broom or rotating brush to get down to the pavement.

Her motto is Shovel, Scatter, Switch.

Shovel means removing the snow and ice as much as possible. Scatter is using as little salt as possible and sparingly. Switch is not using salt when temperatures drop below 15 degrees because it’s no longer effective at those temperatures.

“You need to either just put down sand for traction or use an alternative melter that has the capacity to melt at those lower temperatures. Those do become more expensive. But throwing salt down at that point is really just throwing it away and throwing it into our water,” said Madison.

Only time will tell if those efforts pay off, but either way, Bob and Sue Thome will be back out on the lake as soon as the ice melts, collecting the samples, and hoping for change- and not just for their lake.

“This is just a little example of maybe a far more reaching problem,” said Thome.

If you want to learn more about the impact of salt on lakes, streams, and groundwater, Wisconsin Salt Wise is hosting free webinars during Wisconsin Salt Awareness week which is from January 23rd through the 27th.

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Katie Thoresen is WXPR's News Director/Vice President.
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