Geophysical investigations of groundwater resources in the Kalahari Basin

A regional geoelectrical survey of a semiarid development area of about 4000km2, approximately 300 km NNE of Windhoek, has indicated a quadripartite subdivision of the Kalahari sediments of late Cretaceous to Tertiary age, with a variable development due to considerable undulations of the Damara basement. The Karroo formations are apparently less well represented. A two‐fold interpretative procedure, in which an in itial semiqualitative interpretation involving total longitudinal conductance forms the basis for a subsequent quantitative interpretation, has made it possible to map confidently the major lithological units despite the dearth of reliable stratigraphic control. By relating the geoelectrical data to the groundwater head levels, the degree of penetration and production characteristics of boreholes, and the chemical analyses of water samples, the calcareous sands and sandstones of presumed Middle Kalahari age have been seen to constitute the major aquifer in terms of higher sustained yields of go...