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Characterisation of fractured rocks and evaluation of fracture connectivity are essential for the study of subsurface flow and transport in fractured rock aquifers. In this study, we use a new method to present fracture networks and analyse the connectivity of the fractures, based on the technique of randomly-generated realisations. The application of the method aims to provide more detailed insights into the flow path and dynamics for sustainable utilisation of groundwater in the Table Mountain Group (TMG) aquifers, South Africa. Focusing on a representative wellfield in the TMG, the interpretation and integration of fracture data derived from field measurements, existing geological maps and remotely-sensed imagery, and observed responses of hydraulic tests, led to the development of a conceptual model for fracture network characterisation, which forms the basis of fracture connectivity analysis. The result shows that the a dominant number of the interconnected fractures are in the form of separated fracture clusters (networks) which is considered to be a common connectivity pattern in the TMG rocks and alike. The result also suggests that the connectivity pattern is collectively dependent on such factors as orientation, length, and density of fractures and implies that in a study domain only a small part of the fractures are responsible for flow circulation.

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A toolbar GIS-PMWIN was developed in ArcGIS 9.3 using the embedded Visual Basic for Application. The purpose was to create a linkage between ArcGIS and PMWIN for groundwater modelling with GIS data in PMWIN. Six function modules are developed, including: (i) set model dimension, (ii) modify the current model, (iii) export the grid specification file, (iv) prepare and export the boundary condition files, (v) set top and bottom elevation of layers, and (vi) prepare and export matrix data. Based on the conceptualisation of the study area, the model dimension, discretisation and many value setting processes can be easily carried out in ArcGIS rather than directly in PMWIN, through these function modules. The grid specification file and other input files can be exported as the PMWIN-compatible files which can be directly loaded to PMWIN for modelling. The linkage can be used with a higher version of PMWIN or ArcGIS. It has been applied to mine water modelling in the Far West Rand of the Witwatersrand basin to simulate dewatering and re-watering conditions and scenarios. The modelling practice is elaborated in detail as a case study, and it is demonstrated that the linkage is efficient and easy to use.

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