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Hey Shortwaveers, Emily Quang here, and this week we are doing a deep dive into a vital
“resource that all of life depends on water.”
With producer Burleigh McCoy, hey Burleigh, hey Emily, so okay today I want to talk about a phenomenon that's happening all over the world to fresh water. So we're talking lakes, rivers, groundwater, they are all 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. So here in the Midwest, you know putting millions of tons of road salt into the environment every winter. This is Hillary Dugin, she studies fresh water 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.
“Today on the show, what happens when Earth's fresh water gets too salty?”
And is there anything we can do about it? You're listening to shortwave, the science podcast from NPR. Okay, Barley, so you took a trip to Madison, Wisconsin, to report on this global phenomenon of fresh water getting saltier. So what makes Madison a good place to look into this?
Well, water is a big part of life there. There are these two big lakes on either side of downtown. The University campus is right on the shore of one of them. In the summer, there's a waterfront festival, in the winter, there's a festival in 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 a hundred milligrams per
leader, so it's still technically considered fresh water, but that level is approaching the point that some people could start to taste it in water. That is a huge change. And you said it's happening all over the world, not just in Madison. 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.
“Is road salt the only reason that water around the world is getting saltier?”
It has to be other stuff. 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. Oh, yeah, we talked about that in yesterday's episode and how one way this happens is when
people pump too much water out of their local aquifer and ocean water starts flowing in. And Emily, then there's climate change. So as global temperatures go up, more fresh water evaporates, which makes things saltier because you have less water, but the same amount of salt.
So I'm hearing there's lots of reasons that the world's fresh water is steadily becoming more salty. What is the overall impact then on the environment?
Well, when there's more salt than there should be in the environment, it basically acts
as pollution. It's affecting plants and animals, and even small changes in the salt levels can lead to death. So salt at the levels that are in Madison's lake wing where I right now have been shown to be toxic to fish and snails and so plankton.
The exception to all this are often invasive species. So those are the ones that are more adaptable to new environments, hence why they're invasive. So more salt could actually mean you're giving invasive species more room to thrive over native ones. Oh, yeah.
Wow. So Hilary Dugin, the fresh water researcher we heard from earlier, also points out that for, say, a fish or a plant. But if you're not dying, you still let me stressed by that high salinity, like, think about humans if you drink or eat too much salt, like, you're not going to necessarily die,
but like, you're not going to feel good, and it might be affecting other parts of your health. I don't know what she's talking about. I feel great when I chug a bunch of salt water. And is this salinity impacting creatures beyond fish and snails?
I mean, is it getting into human drinking water?
Yeah, it is. What's the effect there?
So, so Roads salt is usually made out of sodium chloride, and the American Heart Association
recommends 2,300 milligrams of sodium a day as the max that a human should intake.
“But says, actually, you should probably keep it under 1,500 milligrams per day.”
That's ideal. Okay. So now, in medicine, the drinking water comes from wells, not from lakes. But the city officials have measured increasing salt levels in some wells too. Yikes.
Okay. Well, 14 passed 120 milligrams per liter in 2014, which, okay, still probably isn't bad for you unless you're on a low sodium diet, then that amount can add up if you're drinking a few liters a day because people also get salt from their food. And people have documented rising chloride levels and wells across the U.S., Michigan,
New Jersey, Idaho, Arizona. These are in rural places, in urban places, can't the local water plant just filter the salt out? So, I talked to King Doha on about this. He goes by Doha.
“He's a postdoc at the University of Wisconsin, Madison, studying groundwater.”
And he says, you can filter it out, but it is extremely expensive. So, to get the salt out of the water, you've got to boil it to get the distilled water, or you've got to use reverse osmosis. And both are really expensive and requires a lot of energy. Do told me he got into the field because when he was a kid, his family's local water
source was contaminated by a nearby military base in Korea. It started causing health issues for his family, and he remembers having rashes and sometimes vomiting until they moved and the issues went away. So, he's really passionate about keeping drinking water clean.
He is, and he's aware of how big the problem is in Madison.
As chloride, there's a persistent chemical, persistent substance that doesn't go away easily. So, we are still getting the legacy of salt used from 1970s and 1980s. Those are still affecting our lives present day lives. This is making me realize how long salt sticks around. Yeah.
I mean, one of my sources told me that some people in New York have to buy bottled water because their groundwater is too salty to drink. The one family even had to sell their dairy cows because you can buy bottled water for your family, but you can't really buy it for your cows. So the obvious way to slow or stop water from getting saltier is to use less salt.
You can't reverse it, but you can stop it from getting worse from getting saltier. And one person who is advocating for this is Allison Madison. She leads a nonprofit called salt wise, which started when people at the city and county levels in Madison started noticing salt levels going up in drinking water and wastewater.
“I think of it as kind of being a cheerleader for using less salt.”
So salt wise leads trainings and talks. They advocate for things like cleaning up extra salt before it washes away or calibrating equipment so cloud drivers know how much their salt trucks are putting down, which changes with the pavement temperature. So people should also be measuring that and something that has made a big difference in
using less salt is liquid brine. What, brining the roads like the road and turkey for Thanksgiving? The very same Emily. What? So the city now sprays streets when a storm is predicted before the snow falls because
you can actually lose 30% of your salt off the road as the truck drives by so that spraying with brine helps it stay in place, it sticks and it starts working faster. So Allison says it makes it so snow doesn't stick easily to the pavement. So think of cooking with how oil in your pan. Food's going to stick.
The same thing is true on our pavement, if we can prevent the bond from forming between the snow and the pavement, it takes a lot less salt on the back end. So one person who knows about this is Brian Vogue, he's a contractor who does snow removal for small commercial businesses and he used to use a lot of rock salt. But some years ago he saw a YouTube video of someone building their own brine truck.
He's got a mechanical engineer background and likes a challenge, so it sounded like a good idea to me. I just started experimenting a little and then he decided to build his own truck. His own brine truck. His own brine truck.
He's the Honda gas pump engine, bigger flow valves, like two inch and then basically
it's a three lane system of all calculated flow to. And Emily, I got to see this truck. It's essentially a plow truck with a tank and a motor in the back of the truck that sprays the brine out of a bar by his bumper. He even makes his own brine and his rural property.
My redneck homemade brine. And he has a walk behind sidewalk version. It's like his own RTV2.
That sprays brine.
So you would do two passes on a sidewalk there and back and you're done.
“Brine says he wasn't even really thinking about the environment but that seeing excess salt”
on the ground is a pet peeve of his. The properties that I do and I service don't look like those properties that have your tripping on salt. And he says he's noticed a difference.
And once you figure this out, the liquid, you can get it done with way less salt.
I love this person.
“Just the recognition of our problem but the innovation to do something about it.”
Yeah, and Allison says it's solutions like these community-based grass roots that can make a big difference in keeping salt out of freshwater. She told me that the city of Madison has dropped their salt use roughly 40%. 40% is good. Is it enough though?
Because even with everyone using less salt, they're still using salt. So this is what she told me.
“If I was going to tell people we need to stop using salt, I would be laughed out of the room.”
So I kind of have to meet people where they're at and have them know that I understand the realities of their jobs and kind of resident expectations. From environmental perspective, yes, we should stop using salt today. And that's true whether it's road salt or salt from mining or fertilizer.
The solution is both simple and hard.
Stop adding salt to the environment, right? And that was eye-opening for me. I grew up in the Midwest and I got used to seeing salt everywhere. I never thought about where it went. And it's a tough cell in ice-prone areas but a lot of places like Madison have gotten really
serious about at least pulling back their salt use. This story reminded me how solutions can happen if enough people get on board. Burley McCoy, thank you so much for this story. You're welcome. If you liked this episode of Shortwave, please share it with a friend because it really
helps our show out and check out all the episodes in our water series. This episode was produced by Hanna Chan. It was edited by our showrunner Rebecca Ramirez, a rude nire, checked the facts. Jimmy Keely was the audio engineer, I'm Emily Huang, thanks for listening to Shortwave, the science podcast from NPR.
