Water wells in Tuolumne County.

What the completion reports say

• Median depth

  350 ft

  The middle of 4,870 completion reports for newly drilled water-supply wells. Half were finished shallower, half deeper.

• Eighty per cent finish between

  125–775 ft

  A range wider than the median itself, which means the county figure is a weak guide to any one property. What the neighbours hit matters more than what the county did.

• Deepest on record

  1,520 ft

  One well. It says what the county has demanded of a rig at least once, not what it usually asks.

• Water level, where recorded

  55 ft

  How deep the water stood when the well was finished, on the 1,057 reports that recorded it — 22% of the county's wells. This is the measurement Texas's record does not carry at all. It describes the day it was written: levels move with the season, the year and the pumping around them.

• Tested yield, where measured

  18 GPM

  What the well made during the driller's own test, on the 1,826 reports carrying one in gallons per minute. A test is a few hours; it is not a guarantee of what the well sustained afterwards, and it is not a figure to size a system from without a hydrogeologist.

Decade by decade

Wells here have been finished deeper decade by decade: 247 ft in the 1970s, 580 ft in the 2020s — 2.3× the depth. That is what the filings show for the county as a whole. Completion depth follows where and why people drill as much as it follows a water table, so this describes the record rather than explaining it.

• 1970s247 ft469 reports
• 1980s300 ft1,310 reports
• 1990s375 ft1,210 reports
• 2000s450 ft994 reports
• 2010s500 ft366 reports
• 2020s580 ft183 reports

What this page cannot tell you

• Not the water table

  A record, not a reading

  The levels above were written down when each well was finished, some of them forty years ago. They describe those wells on those days. Nothing here is a current measurement, and no average of old filings becomes one.

• Not a yield you can plan on

  A test, not a guarantee

  A driller's test runs for hours. Sustained capacity over a season is a different quantity, measured differently, and most wells on record carry no test at all.

• Not a prediction for a parcel

  4,870 wells, one county

  The median describes the whole county. What matters for one property is the nearest wells in the most similar ground, which is the question Beneath exists to answer.

• Not every well

  Filings only

  Wells drilled before reporting, wells never filed and wells filed with a bad location are missing or misplaced. This is what was submitted, not a census of what exists.

Questions about Tuolumne County wells

How deep are water wells in Tuolumne County, California?

The median water well in Tuolumne County, California is 350 feet deep, based on 4,870 completion reports filed with the Department of Water Resources. Eighty per cent finish between 125 and 775 feet. Where drillers recorded the water level, the median was 55 feet below ground, across 1,057 of those reports. These figures describe wells that were drilled, not what a new well would find.

How deep is the water table in Tuolumne County?

The filed reports do not answer that, and the difference matters. What they carry is the static water level each well recorded on the day it was completed — a median of 55 feet below ground across 1,057 reports in Tuolumne County. Those readings span decades and were taken in different places under different conditions, so they describe wells that were drilled, not the water table today. A current level for one property comes from a measured well nearby, not from an average of old filings.

How many gallons per minute does a well in Tuolumne County produce?

Where drillers tested and filed a figure — 1,826 reports — the median was 18 gallons per minute. A driller's test runs for hours, so it says what the well made that day and not what it sustained through a dry summer. Wells with no filed test are absent from that median entirely, which is most of them.

Are wells in Tuolumne County getting deeper?

On the filed record, yes: a median of 247 feet in the 1970s against 580 feet in the 2020s. Tuolumne is not unusual in this — 54 of the 55 California counties with enough reports to compare show the same direction. What the record cannot say is why: deeper completions follow where people drill and what they are drilling for, as well as what is happening underground.

Does this tell me whether there is water under a specific property?

No. A county median describes 4,870 wells spread across the whole county, and the useful comparison for one parcel is the wells nearest it in the most similar ground. That is a different question, and it is the one Beneath answers — by scoring the whole parcel against the records around it and saying where the evidence is too thin to score.

Counties next door

• Calaveras County — 6,582 wells, 300 ft
• Mariposa County — 6,000 wells, 220 ft
• Amador County — 6,112 wells, 270 ft
• Stanislaus County — 12,655 wells, 200 ft
• San Joaquin County — 14,705 wells, 242 ft
• Merced County — 11,568 wells, 215 ft