Aquifer mapping and groundwater quality in faults and fractures

Abstract

High-definition ground-magnetic surveys have been used extensively in central Victoria to assist with geological mapping and analysis for groundwater exploration. Several wells have been successfully installed, assuming lineaments and domain boundaries are favourable sites for high-yield fracture systems. However, several risk factors in the interpretation can be substantially reduced by using complementary resistivity surveys. In particular, major geological contacts at shallow depth can be confirmed using galvanic resistivity surveys, including rapid-transit capacitive systems. Additional surveys based on the transient electromagnetic (TEM) method can be used to confirm that any presumed fractures do contain water. In addition, TEM data can be used to determine the quality of the water available in order to provide drilling priorities. Numerical models for data obtained in central Victoria are consistent with a semi-vertical fracture system containing water of marginal salinity (1000 ppm TDS).