Where is groundwater deepest in Idaho? All 44 counties ranked
Kootenai County has the deepest wells in Idaho, with a median of 380 ft from 5,626 records. Lemhi County has the shallowest at 66 ft. That 5.8x difference is the single biggest driver of what a well costs, because drilling is priced per foot.
Median well depth for every Idaho county, computed from state well records, with the number of records behind each figure.
By WellDepthPublished
The ranking
Median total depth of reported wells in each of Idaho’s 44 counties, computed from 208,243 Idaho Department of Water Resources well construction records retrieved 2026-09-29.
| # | County | Median depth | Typical range (10th–90th) | Records |
|---|---|---|---|---|
| 1 | Kootenai | 380 ft | 145–684 ft | 5,626 |
| 2 | Elmore | 351 ft | 58–629 ft | 3,139 |
| 3 | Lincoln | 345 ft | 235–591 ft | 1,030 |
| 4 | Clearwater | 305 ft | 120–619 ft | 882 |
| 5 | Lewis | 305 ft | 125–671 ft | 399 |
| 6 | Benewah | 301.5 ft | 145–526 ft | 1,400 |
| 7 | Nez Perce | 300 ft | 103–800 ft | 976 |
| 8 | Latah | 298 ft | 125–500 ft | 1,933 |
| 9 | Idaho | 275 ft | 100–600 ft | 2,757 |
| 10 | Jerome | 270 ft | 179–430 ft | 3,231 |
| 11 | Clark | 256 ft | 100–527 ft | 332 |
| 12 | Boundary | 240.5 ft | 58–555 ft | 1,230 |
| 13 | Cassia | 234 ft | 60–700 ft | 4,458 |
| 14 | Power | 230 ft | 105–455 ft | 1,122 |
| 15 | Boise | 226 ft | 81–460 ft | 2,137 |
| 16 | Owyhee | 215 ft | 62–675 ft | 2,276 |
| 17 | Oneida | 213 ft | 73–420 ft | 1,239 |
| 18 | Bonner | 205 ft | 57–540 ft | 7,311 |
| 19 | Adams | 201 ft | 85–425 ft | 1,417 |
| 20 | Franklin | 201 ft | 73–441 ft | 1,087 |
| 21 | Bonneville | 200 ft | 100–398 ft | 4,502 |
| 22 | Gooding | 192 ft | 100–300 ft | 2,729 |
| 23 | Teton | 185 ft | 84–420 ft | 2,928 |
| 24 | Twin Falls | 180 ft | 75–470 ft | 7,139 |
| 25 | Fremont | 180 ft | 75–400 ft | 3,923 |
| 26 | Minidoka | 168 ft | 34–385 ft | 3,389 |
| 27 | Bannock | 165 ft | 80–370 ft | 3,259 |
| 28 | Camas | 160 ft | 75–345 ft | 690 |
| 29 | Bear Lake | 157 ft | 46–400 ft | 889 |
| 30 | Caribou | 145 ft | 38–344 ft | 1,814 |
| 31 | Canyon | 140 ft | 60–324 ft | 14,209 |
| 32 | Butte | 140 ft | 60–365 ft | 1,012 |
| 33 | Jefferson | 120 ft | 62–260 ft | 6,557 |
| 34 | Ada | 119 ft | 41–353 ft | 13,720 |
| 35 | Bingham | 119 ft | 65–228 ft | 6,511 |
| 36 | Valley | 109 ft | 42–305 ft | 5,411 |
| 37 | Blaine | 103 ft | 40–260 ft | 2,966 |
| 38 | Custer | 100 ft | 42–300 ft | 1,846 |
| 39 | Madison | 98 ft | 60–275 ft | 3,044 |
| 40 | Washington | 93.5 ft | 33–348 ft | 1,970 |
| 41 | Gem | 85 ft | 29–241 ft | 3,398 |
| 42 | Payette | 83 ft | 32–275 ft | 2,803 |
| 43 | Shoshone | 77 ft | 22–420 ft | 733 |
| 44 | Lemhi | 66 ft | 30–308 ft | 2,324 |
141,748 of 208,243 records report a total depth. Counties are ranked on the median of those; the typical range is the 10th to 90th percentile, not the outright extremes.
Why the north is deeper
The pattern in that table is geological, not administrative. The deepest counties — Kootenai, Elmore, Lincoln, Clearwater — sit over harder rock and more broken aquifers, where a driller may pass through several unproductive zones before finding one that produces.
The shallowest sit in valley fill: Lemhi County’s median is 66 ft, against Kootenai’s 380 ft. That is a 5.8x difference in the single number that drives the bill.
What the depth is worth in money
Drilling is quoted per foot, so the ranking converts directly. At published Idaho rates of $35–$60 a foot, a median-depth well runs $13,300–$22,800 in Kootenai County and $2,300–$4,000 in Lemhi.
Those are borehole figures only. Casing, the pump, the pressure tank, electrical and trenching are quoted separately and together often exceed the hole.
What a county figure cannot tell you
A county median describes the wells people drilled and reported, not the ground under one parcel. Groundwater varies over short distances, and these records sit on other people’s property.
Use a county figure to know which questions to ask and roughly what to budget. Use the records near a specific point to know how much that budget could move. Neither is a substitute for a written quote from a licensed Idaho driller.
Sources
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