Borehole success rates in Turkana County vary widely depending on how and where the bores are drilled, but available assessments suggest that without proper hydro‑geophysical surveys, roughly one‑third of bores fail (dry or low‑yield), while well‑planned projects can reach 70–90% success.
What “success rate” means in Turkana
In Turkana, a “successful” borehole is usually one that:
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Finds water at a usable yield.
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Is drilled in a stable aquifer that does not dry up quickly each dry season.
Reports from NGOs and water‑resource studies note that before systematic surveys and modern logging, as few as half of the thousands of boreholes drilled in Turkana were functional, because many were placed in unsuitable zones or in shallow, highly saline layers.
Reported success‑rate ranges
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Unplanned / haphazard drilling
Surveys of groundwater‑development practice in Turkana state that about two in three boreholes drilled without proper geophysical information turn out dry or under‑performing, implying a success rate around 30–40% when no pre‑drilling survey is done. -
With geophysical surveys and professional siting
Where organisations use resistivity or VES‑based targeting, success rates are much higher. For example, Oxfam and similar partners report 70–80% successful bores in their focused Turkana projects.
Some experienced drilling contractors working in Turkana, such as Raeli Hydro, quote internal success rates of about 90–98% when they control the survey and siting, although this reflects their own high‑standard practice rather than a county‑wide average.
Why the rate is not uniformly high
Several factors keep the overall success rate lower across the whole county:
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Drilling without surveys: Many bores are still sunk by small contractors or communities relying on “experience” rather than resistivity/VES, which increases dry‑hole risk.
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Over‑abstraction in hotspots: In areas with heavy groundwater use (e.g., oil‑field‑related abstraction in Lokichar basin), water levels drop, so some previously productive bores decline or fail.
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Mechanical and maintenance failures: Even successful bores often become non‑functional later due to pump failures, poor casing, or lack of maintenance, which distorts the long‑term “success” picture.
Practical takeaway for planning
If you are planning a borehole in Turkana:
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Treat 30–40% as a realistic worst‑case success rate if you skip a geophysical survey.
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Aim for 70–90% by working with a contractor who uses resistivity/VES and who has a documented track record in Turkana.
In short, the average borehole success rate in Turkana is roughly 30–40% when drilling is done without proper surveys, but can rise to 70–90% or higher when professional hydro‑geophysical siting is applied.