How deep will your borehole be? It is the first question every client asks us. The honest answer depends on where you are. A borehole in Mombasa can strike water at 30 metres. In parts of Nairobi or Marsabit you may need more than 300 metres.
This guide gives the typical borehole depth by county in Kenya, for all 47 counties. It also explains why depth changes so much, what water quality risks each region carries, and how to get the exact depth for your own plot.
The Quick Answer
Most boreholes in Kenya are drilled to between 60 and 300 metres. Our own cost guide puts the common range at 100 to 300 metres.
- Shallowest: the coast, often 25 to 100 metres.
- Moderate: Western Kenya and the Central Highlands, usually 40 to 200 metres.
- Deepest: Nairobi, the Machakos hills, parts of the Rift Valley and the arid north, often 150 to 300 metres or more.
These are typical ranges, not promises. Two plots in the same estate can need very different depths. That is why every project should start with a survey.
Borehole Depth by Region
The British Geological Survey notes that boreholes into the Nairobi aquifer are typically 250 to 400 metres deep, while coastal boreholes at Msambweni are 40 to 100 metres and at Baricho just 25 to 60 metres. Source: BGS Hydrogeology of Kenya.
Borehole Depth in All 47 Counties
Type your county in the box to jump straight to it. Ranges are indicative and come from published studies and our field experience across Kenya.
| County | Region | Typical depth (m) | Watch out for |
|---|---|---|---|
| Baringo | Rift Valley | 80 to 250 | Fluoride and salty water near the lakes |
| Bomet | Rift Valley | 60 to 180 | Generally good water |
| Bungoma | Western | 40 to 150 | Generally good water |
| Busia | Western | 40 to 150 | Yields vary |
| Elgeyo Marakwet | Rift Valley | 80 to 250 | Steep sites; depth changes fast |
| Embu | Central Highlands | 60 to 180 | Basement rock in lower areas |
| Garissa | North East | 100 to 250 | Rising salinity in places |
| Homa Bay | Lake Victoria | 80 to 250 | Deep sites in places |
| Isiolo | North | 80 to 250 | Dry holes common without a survey |
| Kajiado | Nairobi Metro | 80 to 300 | Fluoride and salt near Magadi; shallower near Kilimanjaro. See our Kajiado guide |
| Kakamega | Western | 40 to 150 | Generally good water |
| Kericho | Rift Valley | 60 to 180 | Generally good water |
| Kiambu | Nairobi Metro | 150 to 320 | Deeper on high ground such as Limuru and Lari. See our Kiambu guide |
| Kilifi | Coast | 25 to 100 | Salt risk near the coast |
| Kirinyaga | Central Highlands | 60 to 180 | Generally good water |
| Kisii | Lake Victoria | 60 to 150 | Hilly; plan rig access |
| Kisumu | Lake Victoria | 60 to 200 | Water quality varies on the plains |
| Kitui | Lower Eastern | 60 to 200 | Low yields, salty pockets |
| Kwale | Coast | 40 to 100 | Salt water intrusion near the shore |
| Laikipia | Central Highlands | 60 to 200 | Lower yields in the drier east |
| Lamu | Coast | 30 to 100 | Salt risk; protect shallow aquifers |
| Machakos | Lower Eastern | 70 to 320 | Hard rock; fluoride on the Athi plains; hills go deep. See our Machakos guide |
| Makueni | Lower Eastern | 60 to 200 | Hard rock, low yields, salty pockets |
| Mandera | North East | 100 to 300+ | Deep drilling; salty water |
| Marsabit | North | 150 to 300+ | Deep drilling; dry holes common |
| Meru | Central Highlands | 60 to 200 | Yields change with slope |
| Migori | Lake Victoria | 60 to 180 | Yields vary |
| Mombasa | Coast | 25 to 80 | Salt water intrusion |
| Murang’a | Central Highlands | 60 to 180 | Hard volcanic rock in places |
| Nairobi | Nairobi Metro | 150 to 300+ | High fluoride; heavily used upper aquifer. See our Nairobi guide |
| Nakuru | Rift Valley | 100 to 300 | High fluoride; loose volcanic ground. See our Nakuru guide |
| Nandi | Rift Valley | 60 to 180 | Generally good water |
| Narok | Rift Valley | 120 to 300 | Deep on the high plateau |
| Nyamira | Lake Victoria | 60 to 150 | Hilly; plan rig access |
| Nyandarua | Central Highlands | 80 to 200 | High ground; deeper in places |
| Nyeri | Central Highlands | 60 to 180 | Hard volcanic rock in places |
| Samburu | Rift Valley | 80 to 250 | Dry holes common without a survey |
| Siaya | Lake Victoria | 60 to 200 | Yields vary |
| Taita Taveta | Lower Eastern | 40 to 200 | Shallower near Taveta; hard rock elsewhere |
| Tana River | Coast | 40 to 150 | Salty water in places |
| Tharaka Nithi | Central Highlands | 60 to 200 | Dry lowlands need careful siting |
| Trans Nzoia | Rift Valley | 60 to 180 | Generally good water |
| Turkana | North | 60 to 300 | Very salty water in some aquifers |
| Uasin Gishu | Rift Valley | 80 to 200 | Hard volcanic rock |
| Vihiga | Western | 40 to 150 | Generally good water |
| Wajir | North East | 105 to 300 | Salty layers in the Merti aquifer |
| West Pokot | Rift Valley | 60 to 200 | Dry areas need careful siting |
Your exact depth can sit outside these ranges. Hilltops, valleys and old river beds all change the picture. A survey on your land gives the real number.
Why Borehole Depth Changes So Much Across Kenya
Kenya sits on four very different kinds of rock. Each one stores water in its own way.
1. Volcanic rock (Rift Valley, Nairobi, Central)
Volcanic rock covers the middle of the country. Water moves through cracks and old lava layers. The BGS gives an average yield of about 7.5 cubic metres per hour for volcanic aquifers. Depth is often large because the best layers lie deep, especially around Nairobi.
2. Basement rock (Lower Eastern and parts of the North)
Basement rock is old and very hard. Water only sits in fractures, so finding them is everything. Average yields are lower, about 4.4 cubic metres per hour. In Kitui, a groundwater study found average yields of just 6.5 to 6.8 cubic metres per day in Mwingi West and Kitui Rural, according to the Kenya Ground Water Assessment. Siting matters a lot here.
3. Sedimentary rock (North East and parts of the Coast)
Sand and sedimentary layers hold water between grains. The Merti aquifer in Wajir and Garissa is a good example. Successful boreholes there are commonly 105 to 150 metres deep, but salty layers can sit close to fresh ones.
4. Coastal sands and limestone
The coast has the shallowest water in Kenya. The trade off is salt. Pump too hard, or drill too close to the sea, and salt water creeps in. Read our guide on predicting salinity before drilling.
Water Quality Risks by Region
Depth is only half the story. The water you find must also be safe.
- Fluoride: common in the Rift Valley and Nairobi. The BGS reports fluoride above 10 mg per litre in parts of the Nairobi area. The World Health Organization guideline is 1.5 mg per litre (see the WHO drinking water fact sheet).
- Salt: a risk at the coast, near soda lakes such as Magadi and Bogoria, and in parts of the North East.
- Nairobi estates: Nairobi has about 4,000 registered boreholes, and studies have found high salt in water from areas such as Embakasi and Kasarani, as Kenyans.co.ke reported.
- Nakuru: the county is investing in fluoride free water because of the problem, as the Kenya News Agency reported.
Every borehole should get a lab test before you drink the water. See our guide to borehole water testing labs and prices.
How a Survey Finds the Right Depth for Your Plot
A hydrogeological survey costs KES 50,000 with Bonvic Drilling. It gives you the drilling point, the recommended depth, the expected yield and the water quality risks. It is also required for your WRA permit.
Skipping the survey to save money is the most expensive mistake we see. A dry or salty hole costs far more than the survey ever would.
What Depth Means for Your Budget
Depth drives cost more than anything else. A deeper hole means more drilling time, more casing, a stronger pump and more power to lift the water.
- Deeper boreholes need more casing pipe.
- The pump must be sized for the lift height.
- Hard rock slows the rig down.
- Very deep sites may need a bigger rig.
Use our borehole cost calculator for a first estimate, then get a quote based on your survey. If you are still saving up, read how to pay for a borehole in stages.
Frequently Asked Questions
What is the average borehole depth in Kenya?
Most boreholes in Kenya are 60 to 300 metres deep. The coast is shallowest at about 25 to 100 metres, while Nairobi and the arid north often need 150 to 300 metres or more.
How deep is a borehole in Nairobi?
Most new boreholes in Nairobi reach 150 to 300 metres because the upper aquifer is heavily used. Some sites go deeper.
Which part of Kenya has the shallowest boreholes?
The coast. Boreholes in Kilifi, Kwale and Mombasa are often 25 to 100 metres deep, but salt water is a risk near the shore.
Can I know the depth before drilling?
Yes. A hydrogeological survey estimates the depth and yield for your exact plot before any drilling starts. With Bonvic Drilling it costs KES 50,000.
Does a deeper borehole mean better water?
Not always. Deeper water is often better protected, but some deep layers are salty or high in fluoride. Always test the water.
Find Out How Deep Your Borehole Will Be
Bonvic Drilling has drilled boreholes across Kenya since 2010. Tell us your county and we will explain the depth, the risks and the next steps. Contact us or send your location on WhatsApp.
