Deciphering hydrogeochemical processes and groundwater suitability through multivariate and geochemical approaches in...

Madurai, a rapidly growing urban center in South India, faces increasing freshwater demand due to urbanization. In line with Sustainable Development Goal 6 (clean water and sanitation), this study evaluates groundwater quality for drinking and agriculture, highlighting the need for sustainable water management. Fifty groundwater samples were collected and analyzed using standard hydrogeochemical methods to assess seasonal variations and distinguish natural from anthropogenic influences. Results show a significant increase in total dissolved solids (TDS), electrical conductivity (EC), and major ions during the post-monsoon (POM) season, suggesting enhanced mineral leaching and possible surface water contamination. Multivariate statistical analyses provided deeper insights into the relationships among hydrogeochemical variables. Principal component analysis (PCA) indicated a shift from geogenic to anthropogenic influences across seasons, while hierarchical cluster analysis (HCA) revealed greater spatial variability in pre-monsoon (PRM) samples, with POM samples showing more homogeneity due to dilution. Water Quality Index (WQI) analysis showed a seasonal decline in water quality, with more samples rated as 'poor,' 'very poor,' or 'unfit' for drinking in POM. While sodium adsorption ratio (SAR) remained within safe irrigation limits, other indices such as sodium percentage (Na%), permeability index (PI), and Kelly ratio (KR) suggested lower irrigation suitability in POM. Mineral saturation indices indicated continued undersaturation, implying ongoing aquifer mineral dissolution. These findings underscore the need for sustained groundwater monitoring and effective management to safeguard water quality. Achieving SDG 6 requires proactive measures amid growing environmental and anthropogenic pressures.