Geophysical interpretations and groundwater development

Posted on 13 Jun 2022

With an increasing water demand, water supply remains a continued challenge in daily South African livelihood where specialists are challenged to focus on alternative methods for water resources identification to meet a sufficient demand requirement. With the utilization and interpretation through geophysical assessments, the identification and installation of viable groundwater abstraction enables an individual sustainable solution.

 

Various geophysical methods have been developed to accurately drill exploration -, production – and monitoring boreholes. Geophysical data enables an improved understanding of the underlying geological, hydro-geological and structural character. General methods used within the geophysical practice include:

  • Gravity;
  • Seismic;
  • Electromagnetic;
  • Geothermal;
  • Resistivity;
  • Magnetic;
  • Electrical; and
  • Radiometric

The most common methods applied by Hydrogeologists comprise of a combined Resistivity and Electro-magnetic method as discussed below.

 

Resistivity surveys are conducted with an electronic device which measures the flow of electric current through the underlaying surface with the use of probes inserted at regular intervals. Resistivity is defined as the amount of resistance to current flow, therefore the device distinguishes different soil and geological compositions. With low resistive readings, highly weathered zones can be identified for possible groundwater resources.

 

Magnetic surveys are conducted by magneto – or electromagnetic meters, measuring a magnetic field or magnetic dipole moment. Magnetometers measure direction, strength, or relative change of a magnetic field at a particular location in order to identify (through changes) faults, dykes or geological structure contact and/or weathered zones.

 

With the combination of the magnetic anomalies as well as low resistive areas, these geophysical measurements provide accurate identification of probable groundwater sources.

 

Environmental Assurance (Pty) Ltd. (ENVASS) offers a wide range of specialist services and can assist in the accurate siting and developing of exploration -, production – and monitoring boreholes. If you may require a proposal for these services please do not hesitate to contact our highly qualified and experienced specialists at ENVASS on 012 460 9768 or info@envass.co.za

 

Figure 1: Photographic illustration of a Resistivity meter (right) and Magneto meter (left)

 

 

Figure 2: Illustrates Geophysical interpretations and evaluation models