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What is an aquifer? Here's how they affect Texas' water supply.

The Trinity Aquifer and Edwards Aquifer provide water for many beloved Central Texas watering holes.
Lorianne Wilett
KUT News
The Trinity Aquifer and Edwards Aquifer provide water for many beloved Central Texas watering holes.

I’m pretty sure I learned about aquifers in a middle school classroom during a science unit on the water cycle. But, like most people, I’ve entirely forgotten what I learned or didn't pay close attention.

But in the last few years, since I started covering Hays County, I’ve heard the term countless times: How a recent rainfall recharged an aquifer or how an aquifer doesn't have enough water to supply a growing community. But what exactly are aquifers? And how do they allow water from the sky to end up in our faucets?

Let's start with the basic definition: An aquifer is an underground store of water. Sometimes we use that water for everyday life. The Texas Water Development Board estimates about 55% of Texans get their water from aquifers.

Here's what you need to know about aquifers if you live in Central Texas.

Where does the water go?

There are about a dozen major aquifers in the state, the main ones in Central Texas being the Trinity Aquifer and the Edwards Aquifer.

Water goes into the ground through caves, sinkholes and cracks. These “recharge zones” are like the aquifer's personal fill-up area where water can easily fall through. They could be on top of an aquifer or could be miles away. Finally, the water makes its way all the way down to a hole-filled rock layer.

“It’s like Swiss cheese made out of stone,” said David Baker, executive director of the nonprofit The Watershed Association. He said this Swiss cheese layer is hundreds of feet underground, sandwiched between other layers of earth. The water gets trapped there and starts to build up.

“Fifteen stories below us, there’s this… river,” Baker said. “And that's kind of hard to visualize, right?”

As more and more water builds up, so does the pressure. Baker said it’s like a balloon ready to burst at any moment — and then it does. Water flows from the rock layers and fills up beloved watering holes, including Barton Springs and Jacob’s Well.

“It's really magical when it happens, ” he said. “Those 68-degree waters coming out … it's just such a dream to jump in there.”

The water at Jacob’s Well has stopped flowing six times in recorded history, including in 2022 and 2023.
Lorianne Wilett
KUT News
The water at Jacob’s Well has stopped flowing six times in recorded history, including in 2022 and 2023.

When the water stops flowing

So what happens when water isn’t flowing into this Swiss cheese layer? One community in the Texas Hill Country is all too familiar with this.

In the City of Wimberley, the Trinity Aquifer has been the talk of the town since Jacob’s Well stopped flowing for the first time in its recorded history in 2000. Since then, it's happened six more times, including in 2022 and 2023.

“We’ve been experiencing one of the worst droughts ever," said Katherine Sturdivant, education coordinator for the Hays County Parks Department. "We got about half the rain we should have got in 2022. We got about three-quarters of the rain that would be average for 2023."

The less rain that fills up the aquifer, the lower the water pressure in the rock layer, so less water flows out and into Jacob’s Well.

Baker said this cycle where water levels fluctuate is normal and happens in the Trinity Aquifer all the time. However, more water is being pumped out of the aquifer than can be replenished. This is happening because more and more people are moving to the Hill Country and building wells that pull water from the aquifer, Baker said.

“It’s almost like a balloon that's losing pressure," he said. "As you poke more holes in it, the pressure's going out of it. The last eight months we saw too much pumping, not enough rainfall. So we didn't see any flow here.”

The Trinity Aquifer is having a hard time keeping up, but Baker said he believes knowing what an aquifer is is the first step in protecting it.

 The major aquifers of Texas
Texas Water Development Board
The major aquifers of Texas

We’re not the only ones who rely on aquifers

Although the City of Austin gets most of its water from Lake Travis, a portion comes from the Edwards Aquifer. This aquifer is the same one that feeds into Barton Springs. Its deep, dark depths are home to the Austin Blind Salamander.

“This aquifer here is really the only place in the world where these particular species live,” environmental scientist Nathan Bendik said. He’s been studying the salamanders for about 16 years with Austin’s Watershed Protection Department.

When water flows through openings in the ground it can carry pollutants from yards, roadways and construction sites directly into the aquifer. Bendik said the health of the salamander population can be a pretty good indicator of how the aquifer is doing.

“Whether a pipeline burst or a tanker truck spilled on a highway, if that got into the recharge [zone] and came underground, it can very quickly wipe out a large portion of the salamander population,” he said.

Bendik said he and his team work hard to protect and study this delicate system.

“There's a whole variety of organisms that live in the springs here,” he said.

Copyright 2024 KUT News. To see more, visit KUT News.

Maya Fawaz