You're listening to Shortwave from NPR.

Hey, shortwavers, Emily Kwong here, and this week we are doing a deep dive into a vital resource that all of life depends on water.

With producer Burley McCoy, hey Burley.

Hey, Emily.

So, okay, today I want to talk about a phenomenon that's happening all over the world to

freshwater. So we're talking lakes, rivers, groundwater. They are all getting saltier. Wait, what?

Why is freshwater getting saltier? Well, it's for a few reasons, but to figure out why, I recently

took a trip to Madison, Wisconsin, and there, it's

mainly because of all the road salt they put down in the colder months to melt snow and ice.

Wow. So here in the Midwest, we're putting millions of tons of road salt into the environment

every winter. This is Hillary Dugan. She studies freshwater at the University of Wisconsin-Madison,

and she says the road salt eventually washes away

and ends up in the local water.

We're now talking 70-plus years of road salt use,

and what we've seen in the lakes

is the salinity kind of steadily increasing

year after year as more and more salt is put down.

I guess it really does add up that much road salt and it's really impacting the environment.

Yeah, and the drinking water, where it's also starting to show up.

And this is not just Madison's water.

Fresh water is getting saltier all over the world for a lot of reasons beyond road salt.

And it's a problem scientists have just started seriously studying in the last few decades.

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