INEXPENSIVE GEOPHYSICAL INSTRUMENTS FOR GROUNDWATER EXPLORATION IN DEVELOPING COUNTRIES

Geophysical methods are often used to aid in exploration for safe and abundant groundwater. In particular resistivity and seismic refraction methods are helpful in determining depth to bedrock and zones of saturation in the subsurface. However the expense of these instruments ($5000 to $20,000) has resulted in their limited use in developing countries. This talk briefly describes how to construct these devices for less than $250 each. The instruments are small, light and robust and are as accurate as the commercial models for shallow aquifers (less than 35 m deep) where wells can be hand dug, augured or drilled with small portable drill rigs. Seismic sampling rates up to 40,000 samples/second with 16-bit accuracy are possible by using the sound card microphone input available on most laptop computers. A MEMS accelerometer chip serves as a tiny geophone and costs only $13 US. Data interpretation can be accomplished quickly in the field with free software implemented on a laptop computer. A laptop computer can also implement free GIS programs that aid in remote sensing exploration for groundwater sites. A suite of geophysical instruments and software can therefore be assembled for less than $850 US. The instruments have been tested in the field in Tanzania, Chad, Nigeria and Haiti where indigenous well-drillers have been trained to use them. It is hoped that these inexpensive geophysical instruments can be widely distributed among drillers and aid workers in developing countries improving the success rate of water wells.