Conjunctive use of geophysical techniques in optimizing the groundwater potential in the Kunyere and Gomoti areas of the Okavango Delta, Botswana

The lower parts of the Okavango Delta, Botswana comprised of multi layered unconsolidated fresh water aquifer systems developed in the Kalahari Sands and a lower bedrock aquifer within the Karoo Sandstones. The Kalahari aquifers consist of fine to medium sands intervened at various levels by numerous semi-confining units of clays, sandy silts and sandy clays. The lower bedrock aquifer is saline. An investigation of these different aquifer systems was carried using airborne, surface and borehole geophysics in order to quantify the groundwater potentials of the areas. The airborne surveys consisted of magnetic and Electromagnetic surveys, the ground geophysical surveys consisted mainly of Transient Electromagnetic (TEM) and the borehole surveys consisted of gamma and resistivity logging. A comprehensive analysis of the geophysical surveys results along with borehole drilling and logging results assisted in defining the lateral and depth extent of the freshwater aquifers and also guided the successful location, drilling and testing of production boreholes in the study areas. Borehole yields range from as low as 9m ³/hr to as high as 120 m ³/hr in the Kunyere areas whilst in the Gomoti areas yields range from 50 m ³/hr to as high as 110 m ³/hr.