Burleigh McCoy

In the summer, there's a waterfront festival.

In the winter, there's a festival on frozen lake ice.

You just get the feel that the lakes are a part of life there.

So it wasn't a good thing when a few decades ago, people started noticing the salt levels or the salinity of the local lakes were really rising.

Before road salt was introduced, the lakes around Madison had virtually no salt.

Today, the saltiest lake in Madison is Lake Wingra at over 100 milligrams per liter.

So it's still technically considered freshwater, but that level is approaching the point that some people could start to taste it in water.

Yeah, lots of places.

In 2017, Hillary looked at hundreds of lakes in the northern U.S.

and Canada and found that around half of them had gotten saltier.

Basically, if a lake is by a road that's salted, it's super likely some of that salt is going to end up in the lake.

And that's the case globally as well.

Yeah.

So in places where it snows a lot, it is often because of road salt.

But salt can come from runoff, from fertilizer or mining activities.

And another big source is something called seawater intrusion.

And, Emily, then there's climate change.

So as global temperatures go up, more freshwater evaporates.

which makes things saltier because you have less water, but the same amount of salt.

Well, when there's more salt than there should be in the environment, it basically acts as pollution.