The VLF method

Good drinking water is available from the bedrock, but drilling without prior examination rarely water in useful quantities. Efficient water development projects must include carefully conducted geological and geophysical surveys.

VLF transmitter

VLF transmitters, fracture zone containing water and personal with Wadi test instrument.

Highly productive water wells obtained by drilling in rock excavated along joints and fractures. VLF equipment can usually find structures where useful quantities of underground water can get caught in cracks and cavities, so that drillers can choose the most promising areas for water well drillers. For VLF measurements, the use of a remote radio station transmitting on the VLF band (Very Low Frequency, ie. From 15 to 30 kHz and a long wavelength). These radio waves can penetrate deep into the ground (or water) and is in fact used förmilitär communication and navigation. These radio waves is disturbed by comprising electrically conductive formations in the bedrock, which may be electrically conductive rocks or concentrations of certain minerals. They can also be steeply dipping, water-bearing fracture zones. These disturbances or anomalies can be observed using the VLF measurements and used to find the optimal location from where drilling can be done best quantities of groundwater.

Illustration

Illustration of a productive wells and boreholes

Wadi – VLF (used in Puntland 2011) is a state of the art geophysical instrument designed for ease of use. A built-in software makes it possible to interpret the measurements immediately adjacent to the site. But, like other geophysical instruments, finds Wadi just physical structures in the soil and bedrock and can not guarantee water supply in fractures.

VLG

VLG graph on the display of WADI instrument

Examples of anomalies displayed in Wadi-VLF equipment.