Fractured rock systems

This research was first established during the ARC/NWC funded National Centre for Groundwater Research and Training (NCGRT) from 2009-2014, and is now a CWI Flagship Project.

Subprogram 1D: Characterising Fractured Rock Aquifer Systems using hydraulic, hydrochemical and geophysical tools

While relatively robust procedures are available to characterise aquifers comprising primary porosity only (e.g., sandy aquifers), the characterisation of the spatial heterogeneity of fractured rock aquifers remains a significant problem (Cook, 2003; Krasny and Sharp, 2007). de Marsily (2005) identified the development of improved procedures for characterising fractured rock systems as an important priority in a recent review of the subject.

At present we do not know if there is a correlation between fracturing and depth, or fracturing and rock type, or if there is a correlation between the distribution of fractures observed at the surface and the hydraulically significant fractures at depth. Similarly, is there a correlation between the measured hydraulic conductivity and other physical factors such as lithology, alteration of the host rock, or topographic setting? Is there a correlation between fracture density determined from geophysical and lithologic mapping in boreholes and measured hydraulic conductivity? Is there a preferred orientation to the conductive fractures?

This research will focus on the development and use of hydraulic, hydrochemical (major ions, environmental tracers and isotopes) and geophysical (heat, down hole geophysics) tools to investigate fractured rock systems at field sites on or close to the Wellington site. Major and minor ion concentrations and stable and radiogenic isotopes (e.g. 37Cl, 13C, 34S, 87Sr/86Sr, 4He, 14C) from both water and aquifer matrix samples will be established. Cores will be taken from the fractured rock aquifer and tested in the centrifuge. Both worldwide and in Australia, significant water resources are contained in fractured rock aquifers and the appropriate management of these resources is not possible without an adequate understanding of the aquifer characteristics. The project will improve our understanding of groundwater movement and water quality in fractured rock aquifers that vitally underpins fractured rock aquifer management.