Theme unsuitability is noted to have inhibited the accuracy of groundwater potential zones (GWPZs) mapping approach, especially in a semi-arid environment where surface water supply is inadequate. This work, therefore presents a geoscience approach for mapping high-precision GWPZs peculiar to the semi-arid area, using Buffalo catchment, Eastern Cape, South Africa, as a case study. Maps of surficial-lithology, lineament-density, drainage-density, rainfall-distribution, normalized-difference-vegetation-index, topographic-wetness-index, land use/land cover, and land-surface-temperature were produced. These were overlaid based on analytical hierarchical process weightage prioritization at a constituency ratio of 0.087. The model categorizes GWPZs into the good (187 km2), moderate (338 km2), fair (406 km2), poor (185 km2), and very poor (121 km2) zones. The model validation using borehole yield through on the coefficient of determination (R2 = 0.901) and correlation (R = 0.949) indicates a significant replication of ground situation (p value < 0.001). The analysis corroboration shows that the groundwater is mainly hosted by a fractured aquifer where the GWPZs is either good (9.3 l/s) or moderate (5.5 l/s). The overall result indicates that the model approach is reliable and can be adopted for a reliable characterization of GWPZs in any semi-arid/arid environment.

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An integrated geological assessment of groundwater contamination was carried out to determine the nature of the subsurface as well as establish linkages between groundwater and contaminants in the vicinity of the Roundhill landfill, South Africa. Quantitative analysis involved measurement of physico-chemical properties of groundwater samples from two boreholes and a leachate pond within the landfill. Qualitative assessment involved combined measurements of electrical resistivity and time domain induced polarization (IP) across three profiles, using the double-dipole array. The physico-chemical analysis results show the presence of heavy metals (i.e.mercury, lead and arsenic) in groundwater samples in concentrations above the general acceptable limits. Perhaps, the high concentration of these metals could be due to the dumping of toxic and hazardous waste substances on the landfill, contrary to the landfill design and classification. Resistivity and IP pseudo-sections revealed a 4-layered earth structure and anomalous zones of resistivity (112 Ω-m) and low chargeability (1.25 ms) in the top layers. This is indicative of percolating leachate plume in the unsaturated zone. Despite the fact that layer lithologies and stratigraphy pose low risk to groundwater contamination, structural controls such as fractures in the bedrock are favourably disposed to the percolation of contaminants into the groundwater over time. Proper waste classification and inspection should be carried out on the landfill prior to waste disposal.

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