Hydrogeological potential of the deep Ecca Aquifer of the Kalahari, southwestern Botswana

The Matsheng area, located in the Kalahari semi-desert of southwestern Botswana, has in recent years formed the focus for development in the Kgalagadi District. The availability of an adequate groundwater supply is critical to future development in the area, including the establishment of commercial ranching beyond the main centers of settlement. Although groundwater in the Ecca Aquifer in this area was known to be saline, reports persisted that better quality groundwater, perhaps suitable for agriculture, existed, as is the case elsewhere in Botswana. This represented the main prospect of obtaining usable groundwater supplies for potential ranching areas in western Botswana. A detailed assessment has shown that high yielding Ecca aquifer horizons are present across the entire area but the groundwater is highly saline, with no evidence of freshening with depth. There was, in fact, evidence that salinity increased with development of boreholes. It was concluded that the Ecca groundwaters were not usable for any agricultural purpose but the slight improvement in quality on the northern margin of the area indicates that quality improves further to the north.