Electrical Resistivity Survey (ERT) Services

Recently, WWLA has undertaken Electrical Resistivity Tomography (ERT) surveys using our ABEM Terrameter LS system for Bay of Plenty Regional Council (BOPRC), across 4 km of survey lines in the Kaituna area.

The ERT sections successfully delineated a distinct fresh-saline groundwater transition, a salt water wedge, and mapped key lithological units such as unsaturated sands in coastal dunes and saturated gravels inland from the coast.

This work will assist BOPRC in determining locations for saline-intrusion monitoring bores, strengthening long-term groundwater management within the Kaituna Freshwater Management Unit.

ERT Survey Using ABEM LS Terrameter at Kaituna

How it works:  ERT is a geophysical technique for imaging sub-surface geological structures based on electrical resistivity measurements collect at the ground surface.  Subsurface materials such as clays and saline groundwater typically exhibits low resistivity, while materials such as dry sand and gravels generally show higher resistivity.  Electrodes are inserted into the ground surface and connected to a multi core cable which is linked to the Terrameter.  The Terrameter injects an electrical current through selected electrodes pairs in a predefined electrode array and measure the resulting apparent resistivity of the sub-surface.  These apparent resistivity measurements are then processed and inverted to generate 2D resistivity image of the subsurface.  As a result, an indication of sub-surface materials can be mapped to a certain depth without the need for drilling, although drilling is desirable for benchmarking.

This service is often used to target aquifers to determine appropriate locations for bore drilling.