Borehole dilution experiment in a Karoo aquifer in Bloemfontein

Abstract

This paper shows that a borehole dilution experiment using common salt is a useful technique for better understanding of some hydrogeological features of a fractured aquifer. A sense of such tracer experiments was performed in the campus site aquifer, a hydrological experiment site of the Institute for Ground Studies at the University of the Orange Free State in Bloemfontein. It is demonstrated that the model for use in homogeneous aquifers may be adapted in fractured aquifers. Results have revealed valuable information on hydraulic parameters of the fracture system at different scales. Profiles of electrical conductivities monitored in several boreholes can be used to locate horizontal fracture zones in the aquifer. These results may provide an important guide to formulate realistic conceptual models for borehole protection zoning. The experiment can also serve as a reference to future experiments of this kind in Karoo aquifers which cover some 50% of the subcontinent of Southern Africa.