ABSTRACTGeophysical methods have been used for many years to assist in hydrogeological exploration for ground water. For the direct detection of water‐bearing formations, the electrical resistivity method has been effective but relatively slow and costly.More recently, surveys have been conducted successfully with electromagnetic prospecting apparatus developed primarily for the mineral industry. Such equipment has the advantages of greater speed and portability, improved subsurface resolution, and better potential discrimination of conductive aquifers.Electromagnetic methods also can be applied from moving platforms, including fixed‐wing aircraft and helicopters. Detailed and regional surveys conducted in recent years for geological mapping and mineral exploration in Africa and elsewhere have revealed important information on the location and nature of water‐bearing formations and structures. Simultaneous measurements of the magnetic field have been used also to map faults and dikes of potential ground‐water significance.New, wide‐band, digital airborne equipment and processing systems are capable of carrying out rapid, inexpensive studies of subsurface formations to depths of at least 200 meters. Computerized interpretation techniques can produce maps of depth and electrical conductance of a variety of buried aquifers. This information can be of direct assistance to the hydrogeologist or hydrologist in the identification and development of underground‐wat
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