UNDERSTANDING THE GROUNDWATER FORMATIONS UNDERLYING SOUTH CENTRAL TEXAS
In South Central Texas, water law starts with geology. The aquifer beneath your land determines whether your water is fresh, brackish, or even legally usable—and it can make or break a real estate deal, a subdivision plan, or a drilling project.
As a real estate and water law attorney in San Antonio, I frequently advise clients on groundwater rights, conservation district regulations, and water supply issues tied directly to the region’s complex geology. Here’s a practical overview of the major aquifers that supply this part of Texas—and why they matter if you own or plan to buy land.
The map above from the Texas Water Development Board depicts the major aquifers in Texas:
1. The Edwards Aquifer – The Region’s Crown Jewel
If your property lies north, northwest or west of San Antonio—think Bexar, Comal, Hays, Medina, Uvalde and Kinney counties—you may be sitting atop the Edwards Aquifer, one of the most prolific limestone aquifers in the entire United States.
Known for: High-quality, pressurized artesian water
Regulated by: Edwards Aquifer Authority (EAA)
Why it matters: You need a permit to pump, and groundwater rights can be limited or denied depending on historic use.
Note: If you’re buying land within the EAA’s jurisdiction, get legal advice early. This aquifer is heavily regulated, and failure to follow the rules can stop a deal cold. Further, there is a well-defined market for the purchase, sale and lease of Edwards water, and the EAA is involved in that market.
2. The Trinity Aquifer – Water Source for Texas the Hill Country
The Trinity Aquifer underlies parts of Bandera, Kendall, Kerr, Comal and northern Bexar counties. It’s a major source of water for homes and ranches outside of municipal water service.
Known for: Lower flow than Edwards, but widely used for domestic wells
Managed by: Various local Groundwater Conservation Districts (GCDs)
Legal note: Wells in the Trinity often face spacing rules and pumping limits, especially in the upper Hill Country.
If you’re buying rural land with a Trinity well, check with the local GCD about spacing and depth requirements before you build or subdivide.
3. The Carrizo-Wilcox Aquifer – East and South of San Antonio
The Carrizo-Wilcox is a sand-based aquifer — which is increasingly being treated as two distinct formations, even though there is significant transmissivity between the two. It stretches across South and East Texas (really from Louisiana to Mexico) and supplies large-scale municipal and agricultural pumping.
Known for: Massive yield potential and use in water supply projects
Found in: Atascosa, Wilson, Karnes, Guadalupe and Gonzales counties
Regulated by: Multiple groundwater conservation districts — largely based on county lines.
Why it matters: Often tapped for long-term water leasing or export deals—some clients earn significant revenue from Carrizo rights.
Own land east or southeast of San Antonio? Your groundwater may be a valuable commercial asset—and worth a closer legal review.
4. Minor Aquifers – Don’t Overlook These
South Central Texas also hosts lesser-known aquifers like:
Leona Gravel (Uvalde/Frio)
Queen City and Sparta (SE of San Antonio)
West Nueces and Buda formations
While these may not supply large municipalities, they can be critical for residential or livestock use. Legal protection of these wells is just as important, especially in growth areas or during drought.
WHY DOES THE AQUIFER MATTER?
Knowing what aquifer you’re on isn’t just a geological curiosity—it can affect:
The availability, quality and quantity of water
Your right to drill
Whether you need a permit to produce or export water
Required treatment to make the water potable
How much water you can use or sell
Your property’s value
Whether you’re a landowner looking to protect your supply or a buyer planning a new well, the right legal advice can help you avoid mistakes and maximize value. Looking for the best real estate attorney in San Antonio to guide you through groundwater rights and aquifer issues? I’m here to help.
About the Author: Trey Wilson is a San Antonio native and a practicing real estate and water law attorney since 1997. He represents water utilities, landowners, homeowners, and real estate developers across Texas. Trey helps clients navigate complex legal issues involving groundwater rights, property sales, and real estate litigation. Learn more at sanantoniorealestatelawyer.com.
