You're listening to Shortwave from NPR.
Hey, Shortwavers.
Emily Kwong here, continuing our water series, where we dive into all things H2O.
With me is producer and fellow mermaid, Burleigh McCoy.
Hi, Burleigh.
Hi, Emily.
So I'm here with part two, aquifers.
And don't worry, it's okay if you missed part one.
So an aquifer is just an underground layer of rock or materials that holds water.
So it's not like a bathtub?
It's not.
It's more like water between rocks that gets to the surface through wells and springs.
And that groundwater is responsible for about half of the water people use globally.
Wow.
Thank you, aquifers, for keeping us all alive.
Seriously.
And for this episode, I called up someone who has a very close relationship with his local aquifer.
Earliest memory of farming probably would be sleeping on the floor of a combine while my dad drove the combine through the field and harvested corn or wheat.
This is Hayes Kelman.
He's a fifth-generation farmer in western Kansas and he loves it getting his hands in the soil watching a crop grow from seed to harvest.
But around the time he was in high school he noticed something about the water they used to irrigate the family farm.
I started watching how Certain wells were just dropping off significantly, how we were removing a sprinkler from a certain area of land because we didn't have enough water.
So his farm sits above the Ogallala or High Plains Aquifer, which is a huge aquifer.
It spans eight states and it's losing water like a lot of other aquifers around the world.
Sometimes it's because of cities, but a lot of the time it's because of farms using a lot of water.
Right, watering crops.
So what does that mean for farmers like Hayes who rely on aquifers for their livelihood?
Yeah, he says they're growing the same crops, but it's kind of up to chance what he'll harvest, based on how much or how little rain they get.
So he can't plan on a certain yield, which makes the business side of farming really hard.
It's true, and it's getting worse for Hayes and a lot of other farmers all over the world.
But understanding the issue on a global scale, that is a beast of a project.
And it's one that scientists hadn't tackled until a couple of years ago.
Saturday on the show, the state of the world's groundwater and what it means for life on the surface.
Plus, how farmers like Hayes are rethinking how they use their water.
You're listening to Shortwave, the science podcast from NPR.
Okay, Burleigh, so aquifers are clearly very important to life on Earth.
Groundwater is responsible, you said, for half of the water people use globally.
Do we know how many aquifers there are in the world?
So definitely hundreds, maybe thousands.
It turns out that's a tough number for scientists to estimate because aquifers are underground.
Yeah.
So if that's the case, how do scientists get a sense of the state of the world's aquifers?
Yeah.
So a couple of researchers spent years gathering all the aquifer data they could find on close to 1700 aquifers around the world.
And they compiled it into one scientific paper that was published in 2024.
1,700 aquifers.
That's a lot.
It was.
And they estimated that that's three-fourths of all the land being tapped for groundwater.
And the data basically comes from monitoring wells that people monitor the water level of.
And the study team found that in about a third of the aquifer systems they looked at, groundwater levels are going down.
Wow.
Are they drying up entirely?
And what does that mean for life on Earth?
Yeah, that can definitely happen.
It's a huge issue if that's where your drinking water comes from.
Plus, less water in an aquifer can mean the loss of wetland habitat And in some places, draining an aquifer can cause the land to actually sink.
It's called subsidence.
And over time, it also means that you can't recharge that aquifer.
So fill the aquifer back up.
Yeah.
If we don't recharge our aquifers, fill them back up with water.
I imagine it can really alter the landscape.
Yeah.
If the aquifer is by a coast and it gets really low, saltwater can flow in and then contaminate the freshwater in that aquifer.
So why?
In the places where scientists saw water in decline in these aquifers.
How much water are we talking?
So, on average, more than about four inches per year, which imagine if you have a well, that can eventually be catastrophic.
And so a third of those aquifers are losing more than about 20 inches per year.
Deborah Perrone is a water resource engineer at the University of California, Santa Barbara, who worked on the study.
And she says, the places with the most rapid declines tended to be in dry regions around the world with lots of cultivated land.
So in India, the U.S., China, Mexico, Saudi Arabia, and lots of places.
When you have declines in precipitation, you're getting hit twice.
You're getting hit with supply because you no longer have that recharge.
You no longer have the ability to replenish your aquifer.
And then you're also getting hit with demand because now people don't have other sources of water.
They can't do rainfed irrigation.
Their rivers probably have lower flows.
Their reservoirs have less water in them.
So now they're turning to groundwater.
So there really is a domino effect here.
In places where the aquifer is depleting the most, are people just going to run out of water entirely?
That is one possibility.
And we had an episode yesterday that was all about day zero, the predicted day.
A place runs out of water.
And the solution seems simple, right, Emily?
Use less.
But there are a lot of reasons why that's really difficult.
One big issue is that many aquifers span borders.
So multiple countries have to agree on how much water they can use.
And in a lot of places, people across borders already don't get along.
Or they can't agree on water usage.
Yeah.
And our planet...
I mean, it has more than 8 billion people at this point.
This is an uncomfortable question to ask, but does our planet have enough water for all of us?
Yeah, I talked to Filippo Menga about this.
He's a political geographer at the University of Bergamo in Italy and he says the problem isn't the amount of people.
Water withdrawals over time grow much faster than global population.
So it has to do with our lifestyle.
So there is enough water, but not if certain groups of people are using a lot of it.
Right.
And it's a good and a bad thing.
It means we're using way more water than we need, especially in richer countries.
But it also means we can theoretically use less.
True.
But that requires good data and countries reporting honestly how much water they are pulling.
Oh, that sounds like a research nightmare.
Yeah, this is why Debra and her team had such a painstaking time saying something about aquifers globally.
Because the best way to really measure an aquifer's level is by drilling a well and measuring it on the ground.
And if a government doesn't want to do that or doesn't want to share their data, that's kind of it.
The data is a complete mess, yes.
And one of the hardest parts of this project was actually reconciling all the different data elements and trying to make sure that they're comparable across space and time.
So some people might monitor a well every day while others do it every month.
One aquifer may have 20 monitoring wells while another only has five.
And water levels can be different at each one.
Is there no other way to look at aquifer levels besides monitoring these wells?
There are actually these satellites that can tell scientists something about groundwater.
It's a pair of satellites that move around the Earth's orbit in kind of every 90 minutes.
And by measuring the distance between the two satellites you can actually make out how much gravitational field on Earth's surface is changing.
So this is Mohamed Shams Sadoha.
He goes by Shams, and he's a groundwater scientist at University College London.
And he says...
By knowing the distance.
A geodesist can turn that into a field of gravitational anomaly on the Earth's surface.
And the only reason the Earth's gravity will change within a matter of, let's say, a month is because of movement of water from one place to another, from one season to another.
So they're using changes in the gravitational field on the Earth's surface as kind of an indicator of water movement.
Can they see if there's more or less water in an area?
They can, but only by the amount that it's changed by, not the total amount that's there.
And it also can't tell you about water changes in fine detail, like monitoring a single well can.
So, like for Hayes, the farmer we heard from earlier, he's consulting local experts that study his specific area.
The hydrologists and geologists.
They've figured out what amount of water we can pull from the aquifer to become stable.
Because it does have a recharge rate.
And so those experts will tell him how much he needs to reduce his water use over time so that the aquifer can recharge enough to be a renewable resource.
And he says he's ready to make those changes.
Everything we do is for our kids and for the future.
But he admits it's going to be hard.
His farm used to sell a lot of something called milo.
That's a grain that uses less water, but now no one is buying it, and it's just sitting there.
So he still needs to grow the more water-intensive wheat and corn to make a living.
Those are the products people want.
Exactly.
And he points out that if people stop growing as much corn, for example, cattle farmers are going to feel it, because they feed that to their cows and the meat packing plants are affected, because cattle numbers then drop.
So he wonders.
How does that affect the town that I grew up in?
Our economies are based around agriculture.
And irrigation is a massive part of that agriculture.
Yeah.
Everything flows from water.
And he knows something needs to change.
But it's going to have again a domino effect on all these other places and people who he cares about.
Yeah.
And that was kind of the general feeling I got from all of this reporting, Emily.
Everyone knows we need to use less water.
But figuring out how is going to take a lot of time and a lot of agreement.
Yeah.
Are there examples of people actually doing this, like coming to an agreement about how to share groundwater?
Yeah.
One kind of famous one was an agreement in 2010 between Argentina Brazil, Paraguay and Uruguay on how to utilize water from the Guarani Aquifer.
It didn't give specific quotas, but instead promised that countries would share data, avoid causing harm to each other by pulling too much water and, to quote, ensure multiple reasonable, sustainable and equitable use of its water resources.
But even with all of that, implementation has been slow and there's not super clear evidence whether changes are letting this aquifer recharge.
Yeah, tough news.
At the same time, Emily that paper I mentioned earlier Debra's team did discover areas where aquifers that had been losing water in the 80s and 90s were now gaining water in 16 of the aquifer systems they looked at.
Yeah,
And some of these were in places where people were active in their water management, like using less and letting the aquifer recharge.
So it's not all doom and gloom, and I'm actually cautiously optimistic.
So we can do it.
We can live with aquifers and not deplete them entirely.
It is possible, yeah, to turn the tides on our declining aquifers.
Burleigh McCoy, thank you for bringing us this reporting and indeed this whole series about water.
Thanks, Emily.
If you like this episode, please share it with a friend.
And check out yesterday's episode on the idea of day zero and when cities run out of water.
We'll link it in our show notes.
This episode was produced by Rachel Carlson and edited by our showrunner, Rebecca Ramirez.
It was fact-checked by Aru Nair and Angela Zhang.
Jimmy Keeley was the audio engineer.
Thank you so much for listening to Shortwave from NPR.
See you tomorrow.
