Two-dimensional electrical resistivity study of the basement aquifers of the Moshupa Wellfield area, Botswana

In the Moshupa Wellfield area of Botswana, fractured and weathered parts of the basement granitic rocks constitute the dominant local aquifers. Investigation of these aquifers was achieved using 2-D electrical resistivity imaging. The 2-D continuous vertical electrical sounding (CVES) techniques proved a significant advantage over the conventional vertical electrical sounding (VES) technique in that mapping of the subsurface was continuous along a profile. Three 2-D CVES profiles were undertaken in the area of study and the interpretations were used to identify areas with good prospects of finding groundwater in sufficient quantities for small-scale water supply development. Boreholes drilled in the area yielded groundwater in sufficient quantities (∼8 m³/h) to support small-scale domestic water supply and/or livestock and vegetable farming in the area. The results of this study indicate that the 2-D CVES is very useful in selecting borehole sites and if properly employed could greatly assist in choosing productive borehole locations, thus reducing financial losses associated with a poorer choice of boreholes location outside fractured regions.