Chicot Aquifer: how deep the wells are

What this layer is

The Chicot is the youngest and shallowest part of the Gulf Coast Aquifer: beds of sand, silt and clay laid down by rivers and the sea over the last two million years or so (Beaumont, Lissie and Willis). It is at the surface across most of the coastal plain, so most home wells in Harris, Brazoria, Fort Bend, Galveston, Liberty and Jefferson counties draw from it.

Units the model puts in this layer: Beaumont Formation, Montgomery (Lissie) Formation, Bentley Formation and Willis Sand, with Holocene alluvium; includes the model's shallow aquifer system layer.

Checked against the state's own aquifer codes: where our method names this group, the state agrees in 84% of 9,234 wells.

Source of the layers: TWDB's northern Gulf Coast Aquifer model, with cells of about 0.62 mile (1 km).

Key figures

Typical depth (middle half)

180 to 350 feet

Median depth

240 feet

Deepest 10% are past

460 feet

Water level (median)

55 feet

17,991 wells

Yield (median)

50 gpm

14,347 wells, gallons per minute

Wells used

18,759

In the last 10 years

All years on file

50,730

median 248 ft, since 1967

Confidence

Standard (30 or more wells)

Common questions

What a well in this layer costs

At the median depth for this layer (240 feet), a complete home well would cost roughly $8,500 to $21,000: $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 (180 to 350 feet) the range runs from $7,000 to $27,500. 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 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.

For 89% of these wells the report says where the water enters and we use the middle of that interval; for the rest we use the bottom of the hole, which tends to read one layer too deep.

How well it works: In 14,333 wells in the area of the state's northern Gulf Coast Aquifer model (Houston and Southeast Texas) where the State of Texas recorded the aquifer, the formation our method says the well draws from (as grouped on these pages) is the one the state recorded in about 83% of them, and that formation or the one next to it in at least 99%; of the 3,578 of those wells that the state records in the Evangeline, it names the Evangeline for about 51% and the Chicot for most of the rest.

• The layers come from the Texas Water Development Board's northern Gulf Coast Aquifer model, with cells of about 0.62 mile (1 km). It is a regional model, not a survey of any lot.
• The state's model has cells of about 3,277 ft (1 km, 0.62 mile); we read it on a grid of about 0.6 by 0.7 miles. It is not a survey of any lot, so we give ranges.
• Figures go by three groups: Chicot, Evangeline, and Jasper and Catahoula with the Burkeville. The state's records cannot tell the Burkeville, the Jasper and the Catahoula apart at a well (alone, the Burkeville matched 33% and the Catahoula 50%), so they are never named one by one as the formation of a well or a place.
• The line between the Chicot and the Evangeline is drawn differently by different studies. The state's records put about half of their Evangeline wells in what the model draws as the Chicot, mostly deeper wells in Harris, Montgomery, Waller, Liberty and Austin counties. Where both appear, the split is approximate.
• "Near or below the base" means the well ends near or below the base of the Gulf Coast Aquifer (under the Catahoula: Jackson Group, Yegua and older). It is 1.3% of home wells; half of them end within about 85 ft of the base. That is not an error: the model simply ends there.
• The model's top layer is a uniform 49 ft slab for the water table zone, not a rock unit; we merge it into the unit beneath. The model also covers Colorado, Lavaca, Fayette, Wharton and Matagorda counties (outside Groundwater Management Area 14), with the same framework. Texas part only.
• 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/formations/chicot. 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)
• Northern Portion of the Gulf Coast Aquifer System Groundwater Availability Model for Groundwater Management Area 14 Joint Planning (GMA 14 Model). Keester, M.R., Webster, P., Beach, J., Drabek, C., and Chen, Y.H. (KT Groundwater and Advanced Groundwater Solutions), for Groundwater Management Area 14, in cooperation with Lone Star Groundwater Conservation District; layer elevations from GULF-2023 (Ellis and others, 2023, U.S. Geological Survey), 2025, GAM v4.1. TWDB groundwater availability model.
• Ground elevation: Terrain Tiles (Mapzen), Registry of Open Data on AWS
• TWDB well report viewer (each well's official report)