How does the Edwards Aquifer work & why is it so heavily regulated? KSAT Explains

KSAT 12 meteorologists Justin Horne and Sarah Spivey break down what you need to know about San Antonio’s primary source of water

In this episode of KSAT Explains, we're diving into how the Edwards Aquifer works, why it's so heavily regulated and we're learning about the conservative efforts in place that help keep the Edwards Aquifer, and the creatures who call it home, healthy.

SAN ANTONIO – If you’re a regular KSAT 12 viewer, you’ve seen it before - our Weather Authority team reporting on the Edwards Aquifer’s water levels.

The aquifer is the primary source of water for millions of us around South Central Texas and the Hill Country. Its health and future affects us all.

For this episode of KSAT Explains, we’ve partnered with two KSAT 12 meteorologists who report on the aquifer daily. They help us explain how the aquifer works, why it’s so heavily regulated and the conservation efforts in place that help keep the aquifer — and the creatures who call the aquifer home — healthy.

(Watch the full episode in the video player above.)

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How the aquifer works

The Edwards Aquifer and its catchment area cover about 8,000 square miles. It encompasses an area from Edwards and Kinney Counties, and goes as far east as Travis and Hays Counties.

To understand it better, there are three important sections of the aquifer you should know about:

  • The contributing zone, sometimes called the drainage zone, is in the Hill Country.
  • Then there’s the recharge zone, which features areas of the aquifer that are fractured and visible on land. Think of areas like Government Canyon, where limestone is visible.
  • And finally, there’s the artesian zone, where San Antonio lies. In the artesian zone, water is harvested through wells.

In short, here’s how the aquifer works: rain falls on the contributing zone and runs downhill into the recharge zone, where it enters the porous aquifer. Similarly, rain can fall directly on the recharge zone and immediately enter the aquifer.

Then, pressure from all of the water builds up in the artesian zone, and we harvest it by digging wells. The aquifer level you see reported on KSAT 12 by our meteorologists is the level of the water at one of these wells, J-17.

Meteorologist Sarah Spivey explains how the Edwards Aquifer works

Why does the aquifer exist?

To answer the question of why the Edwards Aquifer exists, we have to go back more than 100 million years to when Texas was under shallow seas and San Antonio was a beach.

You can actually see evidence of this in the form of dinosaur tracks at Government Canyon. These tracks are believed to have been formed either on a muddy or sandy beach.

More than 100 million years ago, Texas was under shallow seas. You can see evidence of this in the form of dinosaur tracks at Government Canyon.

Back when Texas was partially underwater, that water was filled with mollusks and clams. They died and over millions of years, their remains have formed karst, or porous limestone, which is what the aquifer is made out of.

Justin Horne goes caving to help you understand the aquifer

One of the best ways to understand the aquifer is to go down into one of the thousands of caves located in the Texas Hill Country. That’s why Justin Horne headed out to Comal County to take a trip down a limestone cave.

The inside of a cave in the Texas Hill Country is the equivalent of a history book on the aquifer

“At one time, the cave was filled with water,” said Geary Schindel, president of the National Speleological Society. “These caves allow us to look at the fabric of the limestone to understand better how groundwater moves through the system, how it goes from recharge to discharge.”

The cave Justin visited was formed millions of years ago. Which brings us back to karst.

“Karst is a landscape that’s characterized by sinkholes and sinking streams in caves and springs,” Schindel said. “It’s also what we call a subsurface system that allows us to transport or move water through it very quickly.”

Just how quickly? Dye testing provides that answer: the groundwater velocity has been measured as great as a mile per day.

The walls of caves also give researchers a good idea of what the aquifer looks like, and how water moves through the system and is eventually discharged at the springs.

Learning facts like these demonstrates how important caves are to those who study the aquifer. And while most of the Hill Country caves are just relics, a few provide actual access to the aquifer.

“There are some caves in Bexar County and Medina Valley and Hays County, where we’ve been able to go through the cave down deep enough, that we’ve actually seen the Edwards Aquifer itself,” Schindel said. “It goes to show you how fragile it is.”

The creation of the Edwards Aquifer Authority

The Edwards Aquifer’s formation is fascinating and dates back millions of years. But it’s during the aquifer’s more recent history where things have become more complicated. These complications eventually led to the creation of the Edwards Aquifer Authority.

“The beginning really stems from a lot of conflict and controversy over what to do about this resource,” said Roland Ruiz, general manager of the Edwards Aquifer Authority.

In the 1980s, the Edwards Aquifer had long been San Antonio’s main water source. But in a rapidly growing city, there was concern about whether there was enough water for everyone.

“Then, much like now, there really weren’t many laws dictating how you could limit groundwater withdrawals,” said Amy Hardberger, director at the Center for Water Law and Policy. “So the Sierra Club in the ‘90s brought an endangered species suit, which was sort of the only way to go about something like that.”

The Sierra Club’s 1991 lawsuit against the U.S. Fish and Wildlife Service cited negligence to provide the necessary protection required by the Endangered Species Act.

In 1993, a federal judge issued a ruling in favor of the Sierra Club, requiring the Texas Water Commission to maintain flows from the Edwards Aquifer-fed Comal and San Marcos springs.

“The judge said ... you either need to manage this or the federal government and me are going to come in and do it,” Hardberger said. “The Legislature has never moved so fast.”

The Edwards Aquifer Authority, or EAA, was created on May 30, 1993, and became fully operational three years later. More than 20 years later, the EAA is by all accounts a success story.

“San Antonio is so much bigger than it was, and the aquifers are doing just fine because we’ve adjusted,” Hardberger said.

The EAA’s mission is three-pronged: manage, enhance and protect the Edwards Aquifer. And over its history, they’ve evolved from mostly managing the aquifer, to shifting more toward protecting and enhancing it.

This brings us to where we are now - a city where uniquely, the local news reports the aquifer every day.

“I think that’s a testament to how important it’s become and how the conservation ethic has taken root,” Ruiz said.

According to Ruiz, the biggest challenge moving forward is making sure the aquifer remains sustainable in the face of a number of potential risks, including climate change and development.

“Is there a threat that the quality of water that gets into the aquifer is going to be compromised at some point? Is there a threat that not only the quality, but the quantity is going to be impacted in some way? So that’s what we’re looking at our field research park,” he said.

The Edwards Aquifer Authority was created on May 30, 1993. More than 20 years later, the EAA is by all accounts, a success story.

The EAA’s mission is not over. One way the EAA and the City of San Antonio are preserving the aquifer for future generations is through conservation easements. Through sales tax funding, the city has bought more than 160,000 acres of conservation easements over the aquifer. A conservation easement simply means the landowners agree not to develop the land in an effort to protect the aquifer.

“What that easement does is it has certain conditions attached to it that prevents development of that property, and it keeps it in this natural state ... to allow the processes of recharge to happen on the property to be uninterrupted by impervious cover and other types of development,” said Thomas Marsalia, EAA protection manager.

EAA quick facts (KSAT 2022)

Protecting Endangered Species

As explained above, the Edwards Aquifer Authority was created to protect species that rely on the aquifer - and to keep the federal government out of managing it. In an effort to avoid further federal involvement, the EAA put together a Habitat Conservation Plan to make sure the numbers of certain species stay at healthy levels.

In total, there are 11 endangered, threatened, or petitioned to be endangered species that call the springs of the Edwards Aquifer home.

In total, there are 11 endangered, threatened, or petitioned to be endangered species that call the springs of the Edwards Aquifer home. (KSAT 2022)

“A lot of people are very surprised that the limits that we have on watering are actually for these tiny little critters,” Hardberger said.

In 2013, five entities with permits to draw from the Edwards Aquifer agreed to the Habitat Conservation Plan. Those entities are the EAA, San Antonio Water System, the City of San Marcos, the City of New Braunfels and Texas State University. You may not hear much about the Habitat Conservation Plan, but it plays a vital role in how the aquifer is managed.

Making sure the protected species that inhabit the aquifer remain at heaty levels is something the EAA believes we al should care about.

“Those species are kind of like the canary in the coal mine so to speak,” Ruiz said. “They’re indicators of the quality and quantity of water in the aquifer. So its not just for their benefit, it’s really for all our benefit that the program exists.”

Part of the EAA’s habitat conservation plan includes turning over every rock to make sure the numbers of certain species stay at a healthy level.

Texas Blind Salamanders

If there’s a poster child for conservation efforts within the Edwards Aquifer, it’s the Texas blind salamander. In fact, the San Marcos Aquatic Resources Center keeps a backup population alive and well just in case something catastrophic happens to the aquifer or the rivers that feed it.

At the San Marcos Aquatic Resources Center, they feed and breed the Texas blind salamanders to keep the population strong. The center says it’s a charismatic species, and that’s what makes it a great mascot for the aquifer.

“Who doesn’t love a salamander that’s kind of odd and a little creepy looking, but cute at the same time?” said Katherine Bockrath, Ph.d., lead researcher at the center. “I think people gravitate to it an its cuteness and its slight creepiness, but also its mystery.”

The blind salamander really is a bit of a mystery. Details about the species’ population are a bit fuzzy. But researchers are working to get some clarity.

“We do some tagging where we catch the animals,” said Adam Daw, Refugia Lead at the San Marcos Aquatic Resources Center. “We’ll release some that we catch and we’ll tag them so that if we catch them again, we’ll know it and can give us an idea of how many are down there.”

In reality, it’s difficult to know just how large or small the Texas blind salamander population is, simply because the tiny creatures live deep underground and underwater in a vast, pitch-black aquifer which spans thousands of miles. But we do know that they’re likely a top predator within the aquifer system - eating worms and small shrimp.

Researchers have also determined that the salamanders can live for quite a long time because of their slow metabolism.

“We have some here that have lived about 10 to 15 years so far,” Daw said. “I wouldn’t be surprised if they live 20 years or more.”

So, if the Texas blind salamanders live for quite some time, and their population is healthy, why do we need to regulate the water level and quality of the aquifer?

“They have very permeable skin,” Bockrath said. “If there’s some contaminant in the water, it’s going to permeate them, too ... they’re super sensitive to environmental changes.”

And, again, these conservation efforts are not just about the protected species.

“We’re actually preserving these ecosystems and these river systems for our use, too,” Bockrath said.

If there is a poster child for conservation efforts within the Edwards Aquifer, it’s the Texas blind salamander.

What is the aquifer report number KSAT 12 reports every day?

Every day our viewers see KSAT 12 Weather Authority meteorologists giving the aquifer report. But have you ever wondered what that level means and where we get that number from? It’s actually measured at the J-17 Index Well, located on Joint Base San Antonio-Fort Sam Houston.

J-17 is literally just a small hole in the floor, surrounded by a box. It was drilled in 1914 to supply water to Fort Sam Houston.

“This is definitely one of the most important wells in Texas,” said Bryan Anderson, EAA data management director. “It definitely, as far as statewide goes, has one of the longest histories.”

Continuous observations started at the well in 1932 by the U.S. Geological Survey. The amount of historic data is what makes J-17 so valuable to aquifer scientists. Today, we get electronic aquifer measurements every 15 minutes.

The aquifer report number comes from a measurement taken at the J-17 well. That number sets water policy for millions.

About the Authors:

Justin Horne is a meteorologist and reporter for KSAT 12 News. When severe weather rolls through, Justin will hop in the KSAT 12 Storm Chaser to safely bring you the latest weather conditions from across South Texas. On top of delivering an accurate forecast, Justin often reports on one of his favorite topics: Texas history.

Sarah Spivey is a San Antonio native who grew up watching KSAT. She has been a proud member of the KSAT Weather Authority Team since 2017. Sarah is a Clark High School and Texas A&M University graduate. She previously worked at KETN News. When Sarah is not busy forecasting, she enjoys hanging out with her husband and cat, and playing music.