Modelling the Subsurface Geology and Groundwater Occurrence of the Matsheumhlope Low Yielding Aquifer in Bulawayo Urban, Zimbabwe

This study is focused on determining the nature, extend and spatial variation of the subsurface and groundwater in the Matsheumhlope low yielding aquifer so as to improve the understanding of groundwater occurrence within Bulawayo Metropolitan area. The abstraction and utilisation of groundwater from crystalline basement complexes have often been hampered by the high rate of borehole failure. For instance, borehole failure in the Matsheumhlope wellfield that characterises the greater part of Bulawayo City, Zimbabwe, is often ascribed to many factors which are yet to be investigated locally and regionally. The electrical resistivity method was used to establish the depth, thickness and sequence of geological units in the low yielding aquifer. Satellite data were used to delineate the lineaments and assess the topographic features of the area. Geological samples obtained from boreholes were correlated with the geophysical pseudo sections to give a better view of the subsurface and groundwater occurrence in the area. Geographic Information Systems (GIS) was used to model the geophysical characteristics of the subsurface giving the potential groundwater occurrence in the area. The study confirmed that the Matsheumhlope aquifer is a heterogeneous unconfined aquifer with a shallow depth to the basement rock in highlands of the study area. The results also showed high spatial variation of subsurface formations and groundwater potential over short distances, thereby indicating the complex nature of mapping basement aquifers. Borehole failure in the area was attributed to the occurrence of shallow depth of the bedrock underlying some parts of the aquifer. Therefore the results of the study recommended that the structural and geodynamic analysis of the fractures of the whole Matsheumhlope aquifer should be done using both structural mapping and geophysical methods.