Application of magnetotelluric geophysical technique in delineation of zones of high groundwater potential for borehole drilling in five communities in the Agona East District, Ghana

Abstract

Hydrogeological investigations to delineate zones of high groundwater potential in five selected communities in the Agona East District of Ghana have been successfully carried out using the magnetotelluric geophysical technique. The technique has successfully been applied to delineate potential zones of high groundwater potential in terms of location and depth-to-aquifer zones. The study has revealed that the apparent electrical resistivity of the subsurface of the study area to a depth of 300 m displays the stratigraphic layers of different resistivities. Eburnean Plutonic suite and the Tamnean Plutonic Suite were the two major geologic materials encountered in the study area. The Eburnean Plutonic suite shows relatively low resistivity rang of 0–480 Ωm at a depth of 0–300 m which indicates the presence of weathered zones capable of holding water. However, the Tamnean Plutonic Suites shows a resistivity range of 200–2800 Ωm which shows that it is a consolidated rock with no developed primary and/or secondary hydrogeological properties such as porosity and permeability. Therefore, the exploration of groundwater in the Tamnean Plutonic Suite depends strictly on the fracture zones which may contain water. Again, the study revealed that the prevailing aquifer systems of the study area are not regional but are controlled by fractures and weathered zones. Therefore, it is highly envisaged that groundwater would be intersected at the saprock region which is the fractured and weathered zone between fresh bedrock and the regolith at the depth of 80–100 m. Also, the study has shown the capability of the magnetotelluric geophysical technique to delineate zones of high groundwater potentials for borehole drilling purpose.