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New technology for groundwater survey
Rainier Dennis
Groundwater is estimated to be 97% of the planet's fresh water supply excluding the poles. Water is indispensable for man's activities on earth. In 1994, the South African government introduced the Reconstruction and Development Programme (RDP) to improve the quality of life for all South Africans. Water supply is an important component of the RDP since one of its objectives is to ensure all households have a clean, safe water supply of at least 25 litres per capita per day within 200 metres of their home. Thus it is important to make groundwater exploration as economical as possible with the highest possible success rate. Groundwater is cheaper to develop than surface water. South Africa has a 15% dependence on groundwater but 80% of the population is dependent on the groundwater. An estimated 12 million people in South Africa has inadequate water supply.
Conventional geophysical methods can only obtain information about the rock matrix, subsurface structures and layers that could bear groundwater, but the presence of water is only determined once drilling commences. These methods have a 40% to 50% success rate in South Africa, which leads to an annual estimated loss of R150 million.
The Electro-seismic Survey System (ESS) was developed by Rainier Dennis whilst completing a M.Sc in Geohydrology at the University of the Free State under Prof. Gerrit van Tonder of the Institute of Groundwater Studies (IGS).
The ESS is based on the phenomenon of electrokinetic signals that are generated through the relative movement of water against the sub-surface rock matrix. This movement of the ground water is established through a seismic wave. This seismic wave can be introduced by a number of methods e.g. a hammer blow, a seismic gun or explosives depending on the depth of interest.
By proper processing and interpretation of the electrokinetic signal measured at the earth surface, the presence of groundwater, the estimated depth and a probable geometry can be determined. What sets this technology apart from conventional geophysical methods is the fact that the presence of water is responsible for the generation of electro-seismic signals.
A fully functional 2-channel prototype has been developed and has a success rate of 85%. The developer was able to quantify the success rate by using the test site at the University of the Free State. The test site has been the subject of study for a number of years making it ideal for testing purposes.
The current prototype under development features 16 "intelligent" wireless probes, spaced on a grid across the area of interest, enabling full 2D and 3D visualization of the probable groundwater geometry.
The estimated release date of the final product is June 2002. Steps have been taken to file for a provisional patent in South Africa.
This technology will be marketed both locally and internationally due to the high global dependence on groundwater. The overseas market is a major market to be targeted.
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