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Water wells in the Upper Trinity, Hays County, Texas

Only 17 home water wells that draw from the Upper Trinity in Hays County, Texas have been reported since 2001, so treat this as a rough guide: the middle half are 330 to 490 feet deep (median 450 ft). It is a minor layer here: just under 1% of the 862 wells the state's model covers; the main one is the Middle Trinity (57%). They run about 60 feet shallower than the county's median well (510 ft). Estimated cost of a complete well at the median depth: $14,000 to $33,500.

This page is based on fewer than 30 wells, so it is kept out of search engines until more reports come in. Treat every figure as a rough guide.

Updated every day from Texas Water Development Board driller reports. Last update: November 11, 2026, using the state file of November 10, 2026.

All wells in Hays CountyUpper Trinity across Texas

Which layer Hays County wells draw from

  • Middle Trinity 57% · 495 wells
  • Lower Trinity 41% · 357 wells
  • Near or below the base of the Trinity 1% · 8 wells
  • Upper Trinity <1% · 2 wells
County home wells covered by the Hill Country Trinity model (in the last 10 years).

Home wells in Hays County

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.

See underground

Well depth (ft)

  • <100
  • 100
  • 200
  • 300
  • 400
  • 600
  • 800+

Dark line: Hays County

Key figures

Typical depth (middle half)
330 to 490 feet
Median depth
450 feet
Deepest 10% are past
508 feet
Water level (median)
198 feet
14 wells
Yield (median)
15 gpm
13 wells, gallons per minute
Wells used
17
Since 2001
Share of the county's wells
<1%
All years on file
17
median 450 ft, since 2001
Confidence
Few wells (10 to 29)

When the wells were finished, the water stood a median 198 feet below the surface (14 wells), well above the bottom: the typical well holds about 252 feet of water.

What this layer is

The Upper Trinity is the upper member of the Glen Rose Limestone: alternating beds of limestone and marl that make the stair-step hills of the Hill Country. It is the first Trinity layer a driller meets and usually the least productive, so many home wells pass through it and are completed deeper.

Checked against the state's own aquifer codes: where our method names this layer, the state agrees in 59% of 347 wells. Read it as the likely layer, not a certain one.

More about the Upper Trinity

Depth over time

Too few wells per period in this layer in Hays County to compare depth over time. Since 2001, 17 home wells have been reported, with a median of 450 feet.

PeriodMedian depth (ft)Wells
2001–2005under 10 wells6
2006–2010under 10 wells6
2011–2015under 10 wells3
2021–2025under 10 wells2

Common questions

How deep is a well in the Upper Trinity in Hays County?

Only 17 home water wells that draw from the Upper Trinity in Hays County, Texas have been reported since 2001, so treat this as a rough guide: the middle half are 330 to 490 feet deep (median 450 ft).

How many Hays County wells draw from this layer?

It is a minor layer here: just under 1% of the 862 wells the state's model covers; the main one is the Middle Trinity (57%). Only 12% of these wells have the water-bearing interval on their report (reports before about 2012 rarely do). For the others we use the bottom of the hole, which tends to read one layer deeper than where the water actually comes from.

How deep does the water stand?

When the wells were finished, the water stood a median 198 feet below the surface (14 wells), well above the bottom: the typical well holds about 252 feet of water.

What a well costs here

At the median depth for this layer in Hays County (450 feet), a complete home well would cost roughly $14,000 to $33,500: $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 (330 to 490 feet) the range runs from $11,000 to $36,000. 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 with a valid depth on their report. 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.

Only 12% of these wells have the water-bearing interval on their report (reports before about 2012 rarely do). For the others we use the bottom of the hole, which tends to read one layer deeper than where the water actually comes from.

How well it works: In 2,665 wells in the Texas Hill Country 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 76% of them, and that layer or the one next to it in at least 98%.

  • The layers come from the Texas Water Development Board's Hill Country Trinity model, with 1 mile cells. 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.
  • "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/hays-county/upper-trinity. License CC BY 4.0. https://doi.org/10.5281/zenodo.24126380.

Sources