01/15/2025 | Press release | Distributed by Public on 01/16/2025 11:06
Transcript
London Darce - Hydrologist, Texas Water Development Board
Hi, my name is London Darce, and I'm a member of the Texas Water Development Board's Groundwater Monitoring Recorder Well Team. We maintain over 250 recorder wells all across the state of Texas. A recorder well is a sensor down a well that's measuring hourly water level data and uplinking that data with telemetry equipment to our website, Water Data for Texas. We use this hourly groundwater level data to create groundwater availability models, to plan for future water use, and to do special projects like this Water and Weather segment looking at recharge and aquifers. We're filming today here at Barton Springs in Austin, Texas, which is a very popular spring located right in the middle of the city.
Water that reaches Barton Springs moves extremely fast underground through holes, conduits, and caves. As you can see in some of this limestone that I have, there's a ton of holes in these rocks. If you poured a glass of water on top, it would immediately move right through it, and this is what the ground underneath our feet looks like everywhere. If water enters a cave in South Austin 10 miles away, it can come right out at Barton Springs just a few days later.
We have nine major and 22 minor aquifers that underlie the State of Texas, and water moves underground to each of them in different ways. In aquifers made of limestone like the Edwards Aquifer, water moves very fast through these caves and through these holes, like I just mentioned. In other aquifers like the Ogallala that underlie the Texas Panhandle, water moves extremely slowly, sometimes taking thousands of years underground before it can be pumped back up at someone's well. Large swaths of the Texas Panhandle are covered in compacted sands, gravels, and clay, which make it very difficult for water to infiltrate down into the aquifer. Water that does enter the Ogallala Aquifer first pools in shallow lakes called playas, where it can then seep down at a rate of 1mm to 21mm per day during the heaviest of floods. Even then, water that does enter the aquifer only accounts for about 36 percent of the total water that pools in these playas.
If we take a look at this hydrograph showing water level data from a recorder well in Dallam County in the far north reaches of the Texas Panhandle, we notice an overall decreasing trend in water levels. North Texas does receive a lot of precipitation in the form of rainfall and snowfall, which is great for refilling our reservoirs and our rivers. But because this water moves so slowly underground, it can be thousands of years before providing recharge to our Ogallala Aquifer.
Let's compare this data to a much more weather-dependent aquifer that underlies much of Central Texas. When we zoom in to the hourly water level data, we can see a much faster response to rainfall events. For example, in Austin, the night of November 4, we received about 1.79 inches of rainfall. Zooming in to the hourly water level data at our recorder well located just off of the creek bed, we see a correspondingly quick rise in aquifer levels. This discharge graph of Walnut Creek shows that the amount of water moving through the creek reached over 1,000 cubic-feet per second during this storm. That water moving down the creek ran down into sinkholes and faults and other small holes in the limestone in order to recharge the aquifer.
Looking at this hydrograph, we can see how this aquifer is similarly responsive to other weather trends. For example, between June and September of 2023, Texas experienced an intense drought. We can see that the water level in the Edwards Aquifer fell over 100 feet at this well and did not rise again until the winter rains came to refill the underground reservoir.
Texas is a huge state with wildly varying geology. Today, we only talked about two of our aquifers and two of the real-time monitoring wells that we maintain to collect data about them. If you want to see more of this data and download it for yourself, check out our website at waterdatafortexas.org.