Using remote sensing to regionalize local precipitation recharge rates obtained from the Chloride Method

Water supply in semiarid Botswana is, to a large extent, based on groundwater. In the planning of a groundwater abstraction scheme, criteria for the sustainability of the abstraction with respect to both quantity and quality have to be satisfied. The most important parameter in the context of quantitative sustainability is the long-term average groundwater recharge together with its spatial distribution. A method is developed to calculate a recharge map that can be used in a groundwater model. The relative distribution of recharge is obtained from remotely sensed data and then calibrated with local values of recharge derived from the Chloride Method. The method was tested for two sites in Botswana, the Chobe Region and Ngamiland.