Large scale quantification of aquifer storage and volumes from the Peninsula and Skurweberg Formations in the southwestern Cape

Abstract

The Western Cape Province of South Africa is a relatively water-scarce area as a result of the Mediterranean climate experienced. Due to the increased usage of groundwater, and the requirement to know how much water is available for use, it is imperative as a 1 st step to establish an initial estimate of groundwater in storage. The storage capacity, namely, the total available storage of the different aquifers, and the storage yield of the fractured quartzitic Peninsula and Skurweberg Formation aquifers of the Table Mountain Group (TMG), are calculated with a spreadsheet and Geographic Information System (GIS) model. This model is based on the aquifer geometry and estimated values (based on measured data) for porosity and specific storage (calculated using the classic Jacob relation). The aquifer geometry is calculated from 1:50 000 and 1:250 000 geological contacts, faults and major fractures, with dips and aquifer formation thickness calculated through structural geology 1 st principles using a Digital Elevation Model (DEM).

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