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Journal of Environmental Hydrology
ISSN 1058-3912 |
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Electronic Journal of the International Association for
Environmental Hydrology
JEH Volume 17 (2009), Paper 9 Posted April 4, 2009 ELECTROMAGNETIC GEOPHYSICAL SURVEY FOR GROUNDWATER EXPLORATION IN THE VOLTAIAN OF NORTHERN GHANA
Larry Pax Chegbeleh1 2World Vision Ghana Rural Water Project (GRWP), Savelugu, Ghana. ABSTRACT The electromagnetic (EM) geophysical method has been used widely in many areas for groundwater prospecting but interpretation of data for accurate location of water bearing features is still a problem. A simple method of data interpretation has been developed and applied in the sedimentary formation of the Voltaian basin of Ghana for groundwater exploration. The interpretation scheme is based on identifying EM highs along parallel traverses of EM profiling data that are presented on one-dimensional (1-D) plots. The results show terrain conductivity distribution in the range of 10-70mS/m for the vertical dipole (VD) mode of the device and 22-79 mS/m for the horizontal dipole (HD) mode pertaining to the general conductivity distribution of the area, using a 20m inter coil separation cable. The conductivities for the HD mode were generally higher than those for the VD mode. The plots show various patterns of EM signature as indications of possible water bearing features. On the basis of defined criteria, the best ranking drill targets were selected for boreholes. The interpretation of EM results helps to delineate water bearing features for a high success drilling rate. The signatures can easily be visualized from the plots facilitating data interpretation. Higher conductivity values for the HD modes suggest the existence of a subsurface clay layer. Reference: Chegbeleh, L.P., J.A. Akudago, M. Nishigaki, and S.N.K. Edusei. 2009. Electromagnetic geophysical survey for groundwater exploration in the Voltaian of Northern Ghana. Journal of Environmental Hydrology, Vol. 17, Paper 9. CONTACT: Larry Pax Chegbeleh Geo-Environmental Evaluation Lab Graduate School of Environmental Science and Technology Faculty of Environmental Science Okayama University, 1-1, Naka 3- Chome, Tsushima Okayama 700-8530, Japan E-mail: larrypax@yahoo.com |
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