Engineers Australia

The hydrogeological significance of fractures within a weathered rock catchment

S. M. Wilkes, T. P. Clement and C. J. Otto

Abstract

Worsley Alumina Pty Ltd (Worsley) operates a bauxite refinery on a lease area occupying the upper reaches of the Augustus River catchment in south Western Australia. This paper presents the results of site characterisation investigations to improve the understanding of the hydrogeology of the study area. Investigations concentrate on the southern portion of the site where sufficient drilling and monitoring data are available to assess the hydrogeology.

Investigations have highlighted the presence of both porous media aquifers within the weathered profile and fractured rock aquifers within the basement rocks. A combination of barometric efficiency measurements and detailed groundwater level measurements has highlighted a strong connection between these aquifers. This connection is thought to be due to the presence of fractured quartz veins found along the margins of dolerite dykes. The results of this investigation have shown that fractures are an important component of the hydrogeology of the Augustus River catchment, which is an example of a weathered rock catchment.