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Pinpointing Groundwater Wells - Somaliland
TEM CASE STUDY ● HORN OF AFRICA, 2024
01 – The challenge
In rural Somaliland, access to clean groundwater is not a given. For communities with limited infrastructure and no reliable water supply, identifying viable well locations is both urgent and costly.
The pastoralist community of Af-Galmadow currently transports water by foot, hours away, twice a week. Each failed borehole attempt represents a significant financial and logistical burden for local partners – traditional test drilling is expensive, slow, and unreliable. A non-invasive approach to subsurface characterisation wasn’t a convenience – it was a necessity.
02 – The context
A groundwater survey commissioned to identify viable well sites for the pastoralist community of Af-Galmadow, located 40 km east of Erigavo in Somaliland’s arid interior.
PARTNER
Dairy without Borders
COUNTRY
Somaliland, Horn of Africa
TERRAIN
Sediment, Limestone
FIELD DAYS
3
TECHNOLOGY
sTEM10
YEAR
2024
Implemented in partnership with Dairy without Borders and the Ramboll Foundation, with NGO partners Iftin and Bayden, and local geophysicist Ahmad Khalif. Geophysical data collected by Peter Thomsen (NIRAS) and Max Halkjær (Geophysical Imaging Partners).
03 – The solution
Ground-Based Transient Electromagnetic Survey
The team deployed the sTEM10 – a compact, portable, ground-based transient electromagnetic scanner — across the survey area outside Erigavo. The instrument transmits controlled electromagnetic pulses into the ground and measures the decaying secondary field to map subsurface resistivity variations, providing high-resolution imaging without any invasive groundwork.
Methodology
01
Survey Planning
TEM soundings were planned densely along several profiles across the priority hydrogeological zones to obtain good resolution of the potential water-bearing structures.
02
sTEM Acquisition
47 high-quality soundings were collected over three field days, capturing subsurface resistivity data to approximately 200 meters depth.
03
Inversion Modelling
Resistivity data were inverted using a 1D-resistivity model in Seequent’s SPIA software, then imported into Workbench and presented as GIS layers and model sections.
04
Hydrogeological Interpretation
Resistivity anomalies were correlated with known local lithologies – sediment cover, limestone, and fractured limestone aquifer zones – to identify and rank borehole targets by confidence.
04 – The results
Continuous resistivity sections revealed a layered subsurface architecture across the survey area – pinpointing discrete saturated zones before a single drill rig was mobilised. The data clearly resolved the aquifer within the fractured limestone, estimated to range 10–30 Ωm in resistivity and interpreted to be 20–50 meters thick. Compared to traditional resistivity methods such as VES, the sTEM10 significantly improved resolution – directly reducing the risk of drilling a dry well.
10–30 Ωm
Aquifer resistivity range
47
High quality soundings collected
20-50 m
Interpreted aquifer thickness
The Region
01
Rainfall
Erigavo receives up to ~400mm of rain a year – while parts of Somaliland’s northern coast get as little as 50mm. Groundwater isn’t a backup here, it’s the primary source.
02
Aquifer Type
Local aquifers sit in the Auradu limestone, where water moves through fractures rather than pore space – making fracture-zone mapping essential before drilling.
03
Water Access
Outside the major rivers, most communities in Somalia depend entirely on boreholes, shallow wells, and springs for drinking water and livestock.
04
The Rock Itself
This is the Auradu Formation – shallow-sea limestone laid down roughly 60 million years ago, now one of the most productive karst aquifers in Somaliland.
05 The impact
A sustainable water supply – and the foundation for a local dairy – within reach for the Af-Galmadow community.
The community of Af-Galmadow relied on water carried by foot, hours away, twice a week. The sTEM survey pinpointed the optimal site for a well field — delivering a reliable water supply and laying the groundwork for a local dairy. Three days of surveying. One community’s future, changed.
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