Hydrogeology and groundwater regime of the Stanford Aquifer, South Africa

Abstract: This study focuses on the Stanford Aquifer which is located in the Overberg region in the Western Cape
of South Africa. The ’Eye’, a captured spring, is used as source for potable water for the local municipality and
extraction have in recent years exceeded the sustainable yield of 33 000 m3/month and a supplementary source is
therefore needed.
The aim of this study is to develop a conceptual model of the aquifer by analysing and compiling years of monitoring
data as well as results from previous studies and field investigations. The aquifer is primarily formed within the
gravelly Klein Brak Formation and to a lesser extent also within the overlying sandy Waenhuiskrans Formation.
Extensive calcrete lenses within the Waenhuiskrans Formation are having a semi-confining effect on the aquifer,
evident from long-term monitoring data. Therefore it is suggested that the aquifer is a confined but leaky type of
aquifer. Furthermore, two palaeochannels (Klein River and Koue Vlakte Palaeochannel) have been identified
within the study area, filled with the Klein Brak Formation they are expected to be high yielding hydrogeological
features. The hydraulic parameters of the Koue Vlakte Palaeochannel were examined through a pump test, which
confirmed the expected high yield nature. Based on the result from the pump test it has been decided to use the
Koue Vlakte Palaeochannel as an additional groundwater source.
Recharge have been estimated using the chloride mass balance and Breede River basin study methods and suggest
that recharge occurs both through precipitation and lateral inflow from adjacent formations. The fact that the Stanford
Aquifer is endorheic, has a large infiltration potential, suggests that recharge through precipitation is significant.
Furthermore, isotopic analysis confirms a meteoric origin of the water within in the Stanford Aquifer.