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How Deep Are Wells in California? Real Depth Data by County
"How deep will my well need to be?" is one of the hardest well-drilling questions to answer in the abstract, because it depends entirely on local geology. California publishes its driller's completion reports as open data, so instead of a national average, here is what 50,511 actual residential wells drilled since 2011 report for depth, broken down by county.
Source and method: California Department of Water Resources Online System for Well Completion Reports (OSWCR), extracted 2026-07-14. Figures include only wells recorded as residential (domestic) use, completed 2011 or later, with a reported depth between 15 and 2,000 ft (to exclude likely data-entry errors). A county is shown only if it has at least 5 qualifying reports. The depth shown is the reported total completed depth of the well; DWR documents known data issues in this dataset, including some incorrect Total Completed Depth values. These are figures self-reported by licensed drillers to the state; neither the California Department of Water Resources nor this site independently verifies them. Treat this as a planning reference, not a guarantee for any specific property, your own site could sit well outside your county's typical range.
Median well depth by county
"Typical range" is the 10th-to-90th-percentile band, i.e. where 80% of reported wells in that county fell. Counties with fewer than 5 qualifying reports since 2011 are omitted rather than shown with a misleading precise figure.
| County | Median depth | Typical range (10th-90th pct) | Reports used |
|---|---|---|---|
| Alameda | 280 ft | 80-420 ft | 202 |
| Alpine | 385 ft | 170-595 ft | 26 |
| Amador | 365 ft | 180-600 ft | 348 |
| Butte | 280 ft | 127-600 ft | 1,347 |
| Calaveras | 400 ft | 200-726 ft | 679 |
| Colusa | 279 ft | 100-600 ft | 176 |
| Contra Costa | 228 ft | 92-360 ft | 336 |
| Del Norte | 55 ft | 38-80 ft | 191 |
| El Dorado | 340 ft | 125-750 ft | 1,397 |
| Fresno | 300 ft | 150-500 ft | 3,835 |
| Glenn | 240 ft | 148-370 ft | 520 |
| Humboldt | 160 ft | 60-280 ft | 792 |
| Imperial | 98 ft | 25-200 ft | 7 |
| Inyo | 164 ft | 75-420 ft | 106 |
| Kern | 400 ft | 220-710 ft | 944 |
| Kings | 360 ft | 60-500 ft | 745 |
| Lake | 195 ft | 88-387 ft | 428 |
| Lassen | 175 ft | 85-415 ft | 284 |
| Los Angeles | 399 ft | 200-660 ft | 396 |
| Madera | 540 ft | 290-640 ft | 2,293 |
| Marin | 255 ft | 45-400 ft | 76 |
| Mariposa | 400 ft | 200-800 ft | 719 |
| Mendocino | 195 ft | 100-300 ft | 1,384 |
| Merced | 290 ft | 120-430 ft | 2,017 |
| Modoc | 240 ft | 130-485 ft | 98 |
| Mono | 223 ft | 125-440 ft | 80 |
| Monterey | 430 ft | 190-790 ft | 460 |
| Napa | 405 ft | 132-660 ft | 806 |
| Nevada | 325 ft | 125-700 ft | 2,216 |
| Orange | 380 ft | 155-800 ft | 34 |
| Placer | 300 ft | 120-700 ft | 1,900 |
| Plumas | 205 ft | 105-402 ft | 416 |
| Riverside | 500 ft | 240-900 ft | 1,991 |
| Sacramento | 245 ft | 125-380 ft | 945 |
| San Benito | 278 ft | 140-560 ft | 202 |
| San Bernardino | 320 ft | 200-560 ft | 1,801 |
| San Diego | 630 ft | 275-1300 ft | 471 |
| San Francisco | 148 ft | 19-190 ft | 10 |
| San Joaquin | 280 ft | 120-360 ft | 1,474 |
| San Luis Obispo | 420 ft | 159-800 ft | 1,284 |
| San Mateo | 238 ft | 59-490 ft | 126 |
| Santa Barbara | 510 ft | 180-874 ft | 410 |
| Santa Clara | 280 ft | 125-500 ft | 658 |
| Santa Cruz | 340 ft | 175-600 ft | 515 |
| Shasta | 200 ft | 104-365 ft | 1,255 |
| Sierra | 200 ft | 101-468 ft | 85 |
| Siskiyou | 204 ft | 88-439 ft | 1,037 |
| Solano | 280 ft | 100-450 ft | 276 |
| Sonoma | 260 ft | 100-500 ft | 3,222 |
| Stanislaus | 240 ft | 133-342 ft | 1,602 |
| Sutter | 119 ft | 51-225 ft | 213 |
| Tehama | 215 ft | 126-400 ft | 1,601 |
| Trinity | 220 ft | 100-380 ft | 1,209 |
| Tulare | 330 ft | 140-460 ft | 3,004 |
| Tuolumne | 500 ft | 235-900 ft | 505 |
| Ventura | 396 ft | 100-880 ft | 162 |
| Yolo | 330 ft | 120-520 ft | 374 |
| Yuba | 300 ft | 112-650 ft | 821 |
How to use this table
Find your county, then use the median and typical-range figures as a starting point when budgeting with the well drilling cost estimator or reading the cost guide. A driller working in your county day-to-day will still know more about your specific property than a county-wide figure can, ask them how your site compares to the county's typical range, and why, before you commit to a per-foot quote with no depth ceiling.
We build these tables state by state from each state's public completion-report data. See also our Texas well depth by county page, or compare it with our Tennessee well depth by county and Florida well depth by county pages.
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