Application Of Electromagnetic Methods For Groundwater Studies

Measurement of the electrical resistivity of the earth has been<br>used for groundwater exploration for many years (Zohdy et al.,<br>1974). Earth resistivity measurements were made using an array of<br>grounded electrodes (Wenner, Schlumberger, dipole-dipole, etc.)<br>with which to inject current into the ground and to measure the<br>resulting potential difference. However, use of grounded<br>electrodes can provide problems in areas of high surface<br>resistivity, where obtaining useful levels of current flow can be<br>difficult. Considerable effort is usually required to locate and<br>move the array so that resistivity surveys tend to be expensive.<br>More generally, the intercoil spacing used in many electromagnetic<br>(EM) methods is shorter than the array length used for conventional<br>resistivity surveys, resulting in improved spatial resolution when<br>used in the profiling mode.