Gold Exploration, Groundwater, Geotechnical investigation, Image the ground and subsurface

Finding reliable groundwater in rural Southeast Asia has traditionally meant drilling blind — expensive, uncertain, and often unsuccessful. Electrical Resistivity Tomography (ERT) has changed that.

Water well drilling Cambodia

What Is ERT?

ERT passes small electrical currents through the ground using an array of electrodes laid out on the surface. By measuring how electrical resistivity varies with depth and distance, we produce a 2D or 3D image of the subsurface — like a geological X-ray.

What ERT Shows Us About Groundwater

Water-saturated soils and rock have lower electrical resistivity than dry material. Clay layers — which act as aquitards — have very low resistivity. Clean sand and gravel aquifers have distinctive resistivity signatures depending on their water content and salinity. By mapping these patterns, we can identify where aquifers exist, how deep they are, and whether they likely contain fresh water.

A Real Example — Preah Vihear, Cambodia

In Preah Vihear Province, previous drilling had consistently failed to find productive water at depths below 30m. Our ERT survey identified a zone of low-resistivity fractured granite at 45–60m depth. A borehole drilled at the geophysically-defined target found a productive aquifer — providing sustainable water supply for the community where previous investigations had failed.

When Should You Consider ERT Before Drilling?

• Sites with no existing well data in the area
• Complex geology with significant lateral variation
• Areas where previous drilling has been unsuccessful
• Large sites where drilling coverage would be expensive
• Saline intrusion suspected — ERT can distinguish fresh from brackish water

ERT is not a replacement for a well — it is what makes your well succeed.

Discuss a Groundwater Investigation