Author(s): David Stephenson
Linked Author(s): David Stephenson
Keywords: Rid; Evaporation; Operation; Recycle; Water resources. Letsibogo dam North South Carrier Pipeline Figure 1 Map of Botswana with eastern dams and water transfer pipeline
Abstract: In an arid country such as Botswana the evaporative loss of water from storage reservoirs on rivers can be greater than the reliable yield. Therefore attempts to minimize evaporation losses must be made. Apart from selecting dams to minimize surface area and covering water surfaces the operational policy can minimize evaporation loss. This requires drawing down water levels as much as possible without increasing the risk of running dry. Operating rules were drafted after modelling the system of four major dams and optimizing operating rules. The principle requires to be able to transfer water between centres if local sources run dry. Groundwater resources should only be exploited when surface reservoirs are drawn down. Then an average aquifer draft within the sustainable yield is feasible. Artificial recharge of groundwater is receiving attention as groundwater storage mimimizes evaporation. The porosity of the Kalahari sands is often low so that geophysical searching for porous aquifers has become a necessity.