Schematic Setup of the Aquifer System in Eastern Caprivi
The Upper Kalahari Aquifer is separated from the Lower Kalahari Aquifer by a probably continuous clay layer (Upper Kalahari Aquitard). It is not yet clear whether a hydraulic connection exists between both aquifers at the Kwando River. The high hydraulic pressure and the high residence times (based on C-14 analyses) indicate that outflow from the lower aquifer may be possible only through upward leakage. In three boreholes Karoo basalt has been encountered underneath the Lower Kalahari Aquifer.
Source: BGR