Assessing groundwater potential using GIS-MCDM and remote sensing techniques: A case study of Franschhoek, South Africa

Abstract

This study focused on the creation of a groundwater potential zones (GWPz) map for an area around the town of Franschhoek, Western Cape Province, South Africa. Parameters including lineament density, aquifer type data, distance to rivers, slope, land use land cover and rainfall were integrated using the geographic information system multi-criteria decision making (GIS-MCDM) weighted overlay method to create the map. Lineaments were obtained from existing geology maps and remote sensing datasets including ArcGIS basemaps, Satellite Pour l'Observation de la Terre (SPOT) 6, Landsat 8, Sentinel-2, Advanced Land Observing Satellite Phased Array type L-band Synthetic Aperture Radar (ALOS PALSAR) and airborne hyperspectral data.  On the GWPz map, high potential zones covered 21% of the area, medium potential zones 42%, low potential zones 27%, and 10% had very low potential. 74% of the boreholes were drilled in the medium and high potential zones. Seismic and stress data were integrated with the GWPz and lineaments and the results showed that areas with high groundwater potential at the intersection of northeast–southwest lineaments would be good exploration targets. Sensitivity analyses involved creating scenario maps based on various weighting options and evaluating the results using Kappa and Pearson correlation coefficients and area under the receiver operating characteristic (ROC) curve (AUC). The scenario maps showed moderate to high correlation (0.67 to 0.96) and Kappa coefficients (23% to 75%) indicated fair to substantial agreement amongst the maps. AUC values ranging from 46% to 66% showed that the models’ abilities to distinguish between the classes ranged from poor to average. The results showed that although the map changes with variations in parameter weights and classification, the high groundwater potential zones are not significantly affected. The findings of the study will assist decision makers in identifying suitable exploration areas, enabling efficient planning, allocation and management of resources.