Investigation of groundwater salinity using geophysical and geochemical approaches: heuningnes catchment coastal aquifer. Western Cape Province, South Africa

Seawater intrusion is recognised as a major factor affecting the quality of groundwater in coastal aquifers around world. To determine occurrence and extent saline prevailing Heuningnes Catchment, 2D resistivity imaging survey was carried out three sites within catchment. Eleven profile lines were conducted using multi-electrode ABEM SAS meter system, employing Wenner Array to map groundwater. A image acquired for these data processed Res2DINV software produce inverse models. The interpretation models revealed zones. first zone characterised by low (1–3 Ω.m); this represents an aquifer filled with water. second has values ranging from (3–30 brackish saturated formation. third denotes sandy layer/sandstone freshwater having high above 30 Ω.m. Geochemical analysis results water samples at 11 locations along electrical also suggest salinity, indicated levels Cl−, Na+, Total Dissolved Solids, Electrical Conductivity. It concluded that some parts study area are impacted seawater intrusion, based on lower < 3 Ω.m ionic ratios which close standard Na+/Cl− SO42−/Cl−. In addition, SO42−/Cl− salinity result dissolution evaporates dilution marine clays rich sodium. Therefore, salinization combined processes. Integration approach proved be significant mapping aquifers. Integrated assessment data, chemical indicate transition saltwater only few actually intrusion. overall not apt human ingestion.