Integrated assessment of groundwater quality in the Grootfontein aquifer, North West Province, South Africa, using hydro-chemical GIS

Groundwater is a critical resource in semi-arid regions, yet its quality is increasingly threatened by anthropogenic pressures and limited monitoring. This study provided a comprehensive assessment of groundwater quality in the Grootfontein aquifer, North West Province, South Africa, by integrating hydrochemical analysis, Geographic Information Systems (GIS), and Water Quality Index (WQI) methodologies. Although similar techniques have been applied elsewhere, this was the first study to apply such an integrated approach to the Grootfontein aquifer, thereby addressing a significant regional knowledge gap in groundwater quality assessment and management. A total of 102 groundwater samples were analysed for major cations (Ca2⁺, Mg2⁺, Na⁺, K⁺), anions (HCO₃⁻, SO₄2⁻, Cl⁻, NO₃⁻), and total hardness (TH). The ionic composition was as follows: Ca2⁺ > Mg2⁺ > Na⁺ > K⁺ and SO₄2⁻ > Cl⁻ > NO₃⁻ > HCO₃⁻. Analysis of the Piper diagram showed a predominance of the Ca–Cl water type, indicating both natural geochemical processes and anthropogenic influences, such as agricultural runoff. Spatial distribution maps developed using GIS-based ordinary Kriging interpolation revealed local areas with high concentrations of salinity and nitrates. Analysis of WQI classified 46% of groundwater samples as having “poor” quality, indicating the need for treatment before domestic or agricultural use. To date, no survey of the WQI or classification of the hydrochemical properties of this aquifer has been conducted, highlighting the novelty and importance of this study. The results provided critical spatial insights into water quality variability and pollution hotspots, informing land use planning and water resources policy in a semi-arid and data-scarce context. This study highlighted the effectiveness of combining hydrochemical tools and spatial analysis to improve groundwater quality monitoring and sustainable aquifer management, providing a framework applicable to other vulnerable groundwater systems globally.