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Water wells in the Dockum Group, Armstrong County, Texas

Home water wells that end at or just below the base of the Ogallala, in the top of the Dockum, in Armstrong County, Texas are typically 250 to 295 feet deep (median 280 ft, 61 wells reported since 2001). It accounts for 27% of the 98 county wells the state's model covers; the main layer is the Ogallala Aquifer (50%). They are about as deep as the county's median well (270 ft). Estimated cost of a complete well at the median depth: $9,500 to $23,500.

Be careful with this group: where our method names the Dockum, the state's own record agrees in only 33% of 4,542 wells (61% for the 1,168 with a screened interval on their report); most of the others are recorded as Ogallala wells. The typical well we put here barely passes the base of the Ogallala, so read it as "at or just below the base of the Ogallala, in the top of the Dockum", not as a confirmed formation.

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 Armstrong CountyDockum Group across Texas

Which layer Armstrong County wells draw from

  • Ogallala Aquifer 50% · 49 wells
  • Dockum Group (at or just below the base of the Ogallala) 27% · 26 wells
  • Near or below the base of the Dockum (or of the Ogallala) 24% · 23 wells

Under Claude, Armstrong County

County home wells covered by the High Plains Aquifer System model (in the last 10 years).

Home wells in Armstrong 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: Armstrong County

Key figures

Typical depth (middle half)
250 to 295 feet
Median depth
280 feet
Deepest 10% are past
315 feet
Water level (median)
176 feet
55 wells
Yield (median)
13.5 gpm
38 wells, gallons per minute
Wells used
61
Since 2001
Share of the county's wells
27%
All years on file
61
median 280 ft, since 2003
Confidence
Standard (30 or more wells)

When the wells were finished, the water stood a median 176 feet below the surface (55 wells).

Which layer Armstrong County wells draw from

  • Ogallala Aquifer 50% · 49 wells
  • Dockum Group (at or just below the base of the Ogallala) 27% · 26 wells
  • Near or below the base of the Dockum (or of the Ogallala) 24% · 23 wells
County home wells covered by the High Plains Aquifer System model (in the last 10 years).

What this layer is

The Dockum is red mudstone, sandstone and conglomerate more than 200 million years old (Triassic) that lies under the Ogallala and the Cretaceous rocks; drillers often call it the red beds. Its sandstones, mostly the lower ones (Santa Rosa), give water to some home wells, for example in Randall and Potter counties. Many wells that just reach the top of the Dockum still draw from the base of the Ogallala, and the state's records usually list them as Ogallala wells.

More about the Dockum Group

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 this layer in Armstrong County are getting deeper. For reference, the median was 285 feet in 2006 to 2010 (13 wells) and 248 feet in 2021 to 2025 (16 wells).

PeriodMedian depth (ft)Wells
2001–2005under 10 wells6
2006–201028513
2011–201526514
2016–202026510
2021–202524816
2026under 10 wells2

Places in Armstrong County with wells in this layer

Common questions

How deep is a well in the Dockum Group in Armstrong County?

Home water wells that end at or just below the base of the Ogallala, in the top of the Dockum, in Armstrong County, Texas are typically 250 to 295 feet deep (median 280 ft, 61 wells reported since 2001).

How many Armstrong County wells draw from this layer?

It accounts for 27% of the 98 county wells the state's model covers; the main layer is the Ogallala Aquifer (50%). Only 44% 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 176 feet below the surface (55 wells).

What a well costs here

At the median depth for this layer in Armstrong County (280 feet), a complete home well would cost roughly $9,500 to $23,500: $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 (250 to 295 feet) the range runs from $9,000 to $24,000. 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 44% 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 22,814 wells in the Texas part of the state's High Plains Aquifer System model (the Panhandle, the South Plains and the Permian Basin) 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 75% of them; when it names the Dockum (4,542 wells), the state's record agrees only about 33% of the time, and most of the others are recorded as Ogallala wells.

  • The layers come from the Texas Water Development Board's High Plains Aquifer System model, with half mile cells, read here on a grid of about 1.2 by 1.4 miles. It is a regional model, not a survey of any lot.
  • The state's model has half mile cells; we read it on a grid of about 1.2 by 1.4 miles, Texas part only. Layers from version 1.01 (2015); the 2025 extension (1.02) did not change them. It is not a survey of any lot, so we give ranges.
  • Figures go by four groups: Ogallala; Pecos Valley; Edwards-Trinity and Rita Blanca (Cretaceous rock under the Ogallala; the Rita Blanca alone matched the state 19%); Dockum (upper and lower together: the state's codes almost never say which). The Edwards-Trinity group joins three aquifers in different places (High Plains around Lubbock, Plateau around Midland and Odessa, Rita Blanca in Dallam and Hartley): county and place pages name the local one where they can.
  • Dockum: when our method names the Dockum, the state's record agrees only 33% of the time over all years (61% for wells with a screened interval, which is 93% of home wells of the last 10 years); most of the rest are recorded as Ogallala wells. The median well we put in the Dockum ends about 18 ft under the base of the Ogallala as the model draws it. So these pages say "at or just below the base of the Ogallala, in the top of the Dockum", never a certain formation. The state's own 2025 report on this model says depth alone overstates the upper Dockum.
  • "Near or below the base" means the well ends near or below the base of the Dockum, or of the Ogallala where there is no Dockum (Permian red beds; Gray, Carson, Donley, Moore and north Potter counties). Half of these wells end within about 51 ft of the base, and the state usually records them as Ogallala or Dockum wells. That is not an error: the model simply ends there.
  • For old wells without a screened interval (bottom of the hole) the method is only a little better than always saying Ogallala (65% against 58%); with an interval it is 89% against 80%. Figures over all years carry that weakness; last 10 years figures rest almost entirely on intervals.
  • 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/armstrong-county/dockum. License CC BY 4.0. https://doi.org/10.5281/zenodo.24126380.

Sources