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Montana water data · County

Jefferson County: well depth, groundwater and water rights

What the public record says about water in Jefferson County: how deep wells go, where the water table sits, what wells produce, which water rights are on file, and which documented environmental sites are nearby. Area statistics orient you; a property report analyzes the records around one specific parcel.

Updated September 2026 · Based on 12,636 public records from MBMG GWIC, Montana DNRC, Montana DEQ, EPA SEMS, EPA UST Finder

Wells on record

5,436

5,222 with recorded depth

Median well depth

180 ft

half of wells 95–300 ft

Median static water level

50 ft

5,023 measurements

Median tested yield

20 gpm

4,994 pump tests

Well depth

How deep are wells in Jefferson County?

Of 5,222 wells with a recorded total depth, the median is 180 feet. Half were drilled between 95 and 300 feet; one in ten went deeper than 440 feet and one in ten found water shallower than 48 feet. Depth is set by local geology and position on the landscape, both of which change over short distances, so the spread matters as much as the median.

under 50 ft
10%
50–100 ft
15%
100–200 ft
27%
200–300 ft
20%
300–500 ft
20%
500 ft and deeper
7%

Static water level

50 ft

median depth to water at rest · half between 20 and 100 ft

The static level is how far below ground the water stands before pumping, measured by the driller at completion. It affects pump setting and operating cost, and it moves with season and with neighbouring use.

Well yield

20 gpm

median tested yield · half between 10 and 30 gpm

7% of tested wells produced under 5 gallons per minute and 56% produced 20 or more. These are short completion tests, not sustained-capacity tests; a household typically needs 3 to 5 gpm with storage.

Drilling activity

Recent well drilling in Jefferson County

984 wells have been completed here since 2016, 60 of them in the last twelve months. The newest log on file was completed August 6, 2026. Records run back to 1860.

What the wells are for

  • Domestic4,459
  • Stockwater444
  • Monitoring256
  • Irrigation197
  • Public Water Supply134

How they were drilled

  • Rotary2,756
  • Air Rotary814
  • Cable511
  • Churn136

Drillers filing well logs in Jefferson County

  • H & L Drilling Inc223 since 2016 · 2026
  • A-10 Drilling207 since 2016 · 2026
  • Western Water Wells102 since 2016 · 2026
  • Okeefe Drilling Co95 since 2016 · 2026
  • Lindsay Drilling Co Inc91 since 2016 · 2026
  • Red Tiger Drilling72 since 2016 · 2026
  • Aaaa Water Well Drilling Inc52 since 2016 · 2025
  • Lindsay Drilling Co27 since 2016 · 2026

Ranked by well logs filed with GWIC, public record only. Not an endorsement, a referral or a paid listing; we have no business relationship with these companies. Verify licensing with the Montana Board of Water Well Contractors before hiring.

Water rights

Water rights on file in Jefferson County

Montana DNRC lists 7,079 water rights in the county: 4,839 groundwater and 2,240 surface water, 6,424 of them active. The median priority date is 1975, and the oldest claim dates to 1858.

Types of right

  • Ground Water Certificate3,407
  • Statement Of Claim3,280
  • Exempt Notice147
  • Provisional Permit133
  • Converted Terminates66

Purposes

  • Stock2,050
  • Domestic1,799
  • Irrigation826
  • Domestic; Lawn And Garden778
  • Domestic; Stock193

DNRC basins

  • 41I2,607
  • 41G2,271
  • 41E2,197
  • 76G4

Area totals describe the neighbourhood, not any one parcel. Montana publishes no authoritative link between a parcel and a water right; whether a right attaches to a specific property is a property-level question that our reports answer with the DNRC abstract linked.

Aquifers and geology

What wells in Jefferson County draw from

Drillers record the aquifer a well is completed in. The units below account for the wells here that carry an aquifer assignment; the median depth beside each is for wells completed in that unit.

  • Boulder Batholith146 wells · 36% · median 166 ft
  • Alluvium (quaternary)74 wells · 18% · median 50 ft
  • Sediments (tertiary)62 wells · 15% · median 121 ft
  • Plutonic Rocks (upper Cretaceous)26 wells · 6% · median 136 ft
  • Sand And Gravel (tertiary)10 wells · 2% · median 109 ft

Aquifer assignments are the driller's, recorded at completion, and many older logs carry none. Absence of an assignment is not evidence about the geology.

Environmental groundwater screening

Documented environmental sites in Jefferson County

Petroleum releases

55

9 open · 46 resolved

Superfund program sites

11

1 on or proposed for the NPL

Registered tank facilities

55

underground storage tanks, current and historical

A documented release or site in the area is not evidence that any particular well is affected. Whether a release reaches a well depends on groundwater flow direction, geology, well depth and construction, the extent of the plume and the cleanup performed. The most recent release reported here dates to 2024. A property report screens the sites within a quarter, half and one mile of a specific parcel and links the agency records.