Updated 2026-10-23
When drilling a borehole, how do you decide at what depth to stop if you haven't struck water?
Set the stopping depth before drilling, not at the rig: a survey should give the depth of the water-bearing zone, and the driller stops once that zone is reached and tested. Going deeper without a target often fails in hard rock: in Bavaria four dry holes reached 118 m, while WaterLocation found 200 m³ a day at 22 m nearby; in Catalonia the water lay below 100+ m of clay, at 136 m.
Why "a few more metres" is a weak rule
Most drillers stop a dry hole for practical reasons: the agreed budget, the rig's capacity, or a rule of thumb about the area. None of these says where the water is.
- In granite, basalt, dolomite and limestone water moves through fractures. If the hole is beside the fracture rather than on it, more metres of solid rock usually add cost, not water.
- Under thick clay the opposite happens: holes are often stopped inside the clay, just above the water-bearing zone underneath it.
So the right stopping depth depends on the site, and it should be known before drilling starts.
Depths in WaterLocation projects
| Site | Earlier holes | Where water was reached | Yield |
|---|---|---|---|
| Mitterfirmiansreut, Germany (granite hilltop) | Four empty boreholes up to 118 m | 22 m, 47 m from one of the empty holes | 200 m³/day |
| Catalonia, Spain (100+ m of clay and loam) | Several failed boreholes | 136 m, right below the clay; static level 39 m | 648 m³/day (state pumping test) |
| Altmannstein, Germany (Jurassic limestone) | An 80 m borehole gave 2 l/s | 88 m, static level 56 m | 10 l/s (864 m³/day) |
| Desert site, Saudi Arabia | Negative geological forecasts | First artesian water at 43 m as forecast; main source at 150 m | 1,000 m³/day |
| Kalahari, Namibia (dolomite and rock) | Nine wells; one gave water all year, but not enough | 57 m (240 m well) and 21 m (132 m well) | 100 and 350+ m³/day |
Figures from WaterLocation project reports. The pattern: water was reached at the depth of a specific zone, sometimes much shallower than the failed holes, sometimes deeper than drillers expected.
What to agree with the driller before the rig arrives
- Target depth of the water-bearing zone, from the survey report, and a maximum depth you will pay for.
- Logging: depth of every water strike, what was drilled through, and airlift flow at regular intervals.
- A decision point: if the target zone is passed with no water strike, stop and review the log instead of continuing metre by metre.
- Testing: when water comes in, a flow test on site and then a pumping test to compare the yield with your demand.
- Rig and fluid: on WaterLocation sites, an air-flush rig; if drilling fluid is unavoidable, cellulose-based only.
How WaterLocation sets the depth
WaterLocation surveys the site for water-bearing fractures and zones and gives a drilling point, the depth to the water-bearing zone, a forecast yield and a drilling specification. A licensed local driller drills to that specification. The discovery fee is paid only after a pumping test confirms the water at that point and depth. Surveys are quoted per site.
See also what to do after a dry borehole, can a survey predict depth and yield and drilling through deep clay.
Sources
Questions
How deep are water boreholes usually?
In hard rock, usually less than 200 m; with thick clay or saline layers it can be deeper. In WaterLocation projects where the report gives the depth, water was reached between 14 m and 136 m.
Only dust came out of my borehole. Will water seep in later?
Sometimes a little water collects over hours or days from small seeps, but a rising level in the hole is not the same as yield. Only a pumping test shows whether the hole can supply what you need; if it cannot, a new point chosen by a survey is usually the better next step.
Who should decide when to stop: the driller or the survey?
The survey should set the target depth; the driller decides how to get there safely and reports what the hole shows. Agree on both before drilling, so the stopping decision is not made under pressure at the rig.