Water wells in the Southern Trinity Groundwater Conservation District
Home water wells inside the Southern Trinity Groundwater Conservation District (McLennan County, Texas) vary a lot in depth: the middle half are 80 to 1,180 feet deep (median 1,100 ft, 87 wells drilled in the last 10 years), so look at the wells closest to the tract. No single layer dominates: 49% draw from the lower Trinity (Twin Mountains and Travis Peak) and 30% from younger formations above the Woodbine, according to the state's Northern Trinity and Woodbine model (TWDB). Over the last three full years drillers reported about 7 new home wells a year; the peak was 14 in 2019. Estimated cost of a complete well at the median depth: $30,000 to $72,500.
Updated every day from Texas Water Development Board driller reports. Last update: November 11, 2026, using the state file of November 10, 2026.
Under the center of the Southern Trinity GCD
District boundary from TWDB's file current as of November 2019. Later changes are not shown.
Digging in…
Home wells in and around the Southern Trinity GCD
Each dot is a home well from a state driller report, colored by depth. Tap one for its details and official report. Tap an empty spot to see what is under that point.
Well depth (ft)
- <100
- 100
- 200
- 300
- 400
- 600
- 800+
Dark line: the district boundary (TWDB, 2019)
Green: aquifer mapped by the state
Key figures
- Typical depth (middle half)
- 80 to 1,180 feet
- Median depth
- 1,100 feet
- Deepest 10% are past
- 1,260 feet
- Water level (median)
- 621 feet
- 81 wells
- Yield (median)
- 16 gpm
- 72 wells, gallons per minute
- Wells used
- 87
- In the last 10 years
- Counties
- 1
- All years on file
- 143
- median 1,080 ft, since 2001
- Confidence
- Standard (30 or more wells)
When the wells were finished, the water stood a median 621 feet below the surface (81 wells).
New home wells per year
Over the last three full years drillers reported about 7 new home wells a year; the peak was 14 in 2019.
Show the data table
| Year | Wells |
|---|---|
| 2003 | 4 |
| 2004 | 2 |
| 2005 | 5 |
| 2006 | 2 |
| 2007 | 6 |
| 2009 | 5 |
| 2010 | 4 |
| 2011 | 5 |
| 2012 | 2 |
| 2013 | 6 |
| 2014 | 5 |
| 2015 | 6 |
| 2016 | 4 |
| 2017 | 12 |
| 2018 | 7 |
| 2019 | 14 |
| 2020 | 12 |
| 2021 | 8 |
| 2022 | 7 |
| 2023 | 6 |
| 2024 | 7 |
| 2025 | 9 |
| 2026 | 4 |
Which formation the wells draw from
No single layer dominates: 49% draw from the lower Trinity (Twin Mountains and Travis Peak) and 30% from younger formations above the Woodbine, according to the state's Northern Trinity and Woodbine model (TWDB).
| Layer (state's model) | Share | Wells | Typical depth (ft) |
|---|---|---|---|
| Lower TrinityTwin Mountains and Travis Peak | 49% | 43 | 1,118–1,220 |
| Above the Woodbine | 30% | 26 | 55–80 |
| Washita and Fredericksburg | 14% | 12 | 80–85 |
| Near or below the base of the Trinity | 6% | 5 | 1,120–1,200 |
| Upper TrinityPaluxy and Glen Rose | 1% | 1 | — |
For 97% of these wells the report says where the water enters (the screen or the open hole), and we use the middle of that interval.
Depth over time
There are not enough wells in both 2003 to 2007 and 2021 to 2025 (at least 30 in each) to say with confidence whether wells in the district are getting deeper. For reference, the median was 712 feet in 2001 to 2005 (12 wells) and 1,100 feet in 2021 to 2025 (37 wells).
| Period | Median depth (ft) | Wells |
|---|---|---|
| 2001–2005 | 712 | 12 |
| 2006–2010 | 1,078 | 17 |
| 2011–2015 | 1,120 | 24 |
| 2016–2020 | 1,100 | 49 |
| 2021–2025 | 1,100 | 37 |
| 2026 | under 10 wells | 4 |
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Common questions
How deep are wells in the Southern Trinity GCD?
Home water wells inside the Southern Trinity Groundwater Conservation District (McLennan County, Texas) vary a lot in depth: the middle half are 80 to 1,180 feet deep (median 1,100 ft, 87 wells drilled in the last 10 years), so look at the wells closest to the tract.
Which formation do wells in the district draw from?
No single layer dominates: 49% draw from the lower Trinity (Twin Mountains and Travis Peak) and 30% from younger formations above the Woodbine, according to the state's Northern Trinity and Woodbine model (TWDB).
What does a groundwater conservation district do?
In Texas, districts are the local authority over groundwater: they can require registration or permits for new wells, set spacing from other wells and property lines, and limit pumping. Each district writes its own rules, so ask the Southern Trinity Groundwater Conservation District before drilling inside it.
What a well costs here
At the median depth for the district (1,100 feet), a complete home well would cost roughly $30,000 to $72,500: $25 to $60 per foot for drilling, casing and seal, plus $2,500 to $6,500 for the pump, pressure tank, controls and hookup at the well. Across the whole middle half of depths (80 to 1,180 feet) the range runs from $4,500 to $77,500. This is TerraFunded's estimate from published Texas prices, not a quote, and it leaves out trenching and the line to the house. Get prices from at least two licensed drillers.
How these numbers are made
We count new and replacement domestic (home) wells whose coordinates fall inside the district boundary. We use the last 10 years when there are at least 30 wells; otherwise all since 2001. The median is the middle well and the middle half runs from the 25th to the 75th percentile.
To tell which layer a well draws from, we take the ground elevation at its location, subtract the depth of the interval where water enters (or the bottom of the hole when the report does not give one) and see which layer of the state's model that point falls in.
For 97% of these wells the report says where the water enters (the screen or the open hole), and we use the middle of that interval.
How well it works: In 7,977 wells in the area of the state's Northern Trinity and Woodbine model (North and Central Texas) where the State of Texas recorded the aquifer, our estimate of the formation the well draws from names the same layer of the state's model in about 74% of them, and that layer or the one next to it in at least 95%; among the 3,130 of those wells that the state places in a Trinity layer (Paluxy to Hosston) it is about 56%.
- The layers come from the Texas Water Development Board's Northern Trinity and Woodbine model, with quarter mile cells, summarized here to about 1.3 miles. It is a regional model, not a survey of any lot: between one model point and the next, the real depth of each layer can differ.
- In this model every layer is at least 30 feet thick, even where the real rock is thinner or missing. Thin layers and the edges of the model are approximate.
- Inside the Trinity this atlas does not name single model layers: it groups the Paluxy and Glen Rose (upper Trinity) and groups the Hensell, Pearsall and Hosston (lower Trinity, Twin Mountains and Travis Peak), because the check against the state's codes shows the method cannot separate them reliably.
- "Near or below the base of the Trinity" means the well reaches the bottom of the model or passes it, often by tens of feet. Older rock that the model does not include may lie there.
- We never use the model's water levels. The water level on this page is the one each driller measured when the well was finished.
These are depths of real wells drilled nearby, not a promise about any property. Groundwater can change over short distances and with drought. A licensed water well driller can tell you what to expect on a specific tract.
Read the full methodology · Download the data (CSV, CC BY 4.0)
How to cite
TerraFunded (2026). Texas Well Atlas: Underground. From Texas Water Development Board driller reports and groundwater availability models (data as of November 10, 2026). https://terrafunded.com/wells/districts/southern-trinity-groundwater-conservation-district. License CC BY 4.0. https://doi.org/10.5281/zenodo.24126380.
Sources
- Submitted Driller's Reports database, Texas Water Development Board (TWDB) (file of November 10, 2026)
- Hydrogeology and Documentation of the Northern Trinity and Woodbine Aquifer System Groundwater Availability Model (NTGAM). Ellis, J., Prieto-Estrada, A., Osborne, A., Deeds, N., White, J., and Keester, M. (INTERA Incorporated), for the North Texas Groundwater Conservation District and Groundwater Management Area 8, 2025, GAM v3.01. TWDB groundwater availability model.
- Groundwater conservation district boundaries, TWDB (current as of November 2019)
- Ground elevation: Terrain Tiles (Mapzen), Registry of Open Data on AWS
- TWDB well report viewer (each well's official report)