Integrated Hydrogeochemical and seasonal assessment of groundwater using ionic ratios, gibbs and piper methods in Madurai North Taluk

A comprehensive hydrogeochemical and temporal assessment of groundwater quality was conducted in Madurai North Taluk, Tamil Nadu, India, to evaluate its suitability for drinking over 15 years (2008–2022). Groundwater samples collected during pre- and post-monsoon seasons were analyzed for major physicochemical parameters. Hydrogeochemical processes controlling groundwater composition were interpreted using Gibbs diagrams, Piper trilinear diagram, ionic ratio plots, and multivariate statistical techniques. TDS ranged from 531 to 4251 mg/L, with elevated concentrations of Na⁺ (1150 mg/L), Ca²⁺ (512 mg/L), Cl⁻ (1758 mg/L), and HCO₃⁻ (1104.1 mg/L), often exceeding BIS and WHO drinking water limits. Gibbs diagram results indicate that rock–water interaction is the dominant mechanism controlling groundwater chemistry in both seasons, accounting for more than 60% of the samples. This is attributed to prolonged interaction with crystalline rocks such as granite, gneiss, and charnockite. Evaporation dominance observed in certain years (2013, 2016, and 2020) suggests salinity enrichment under semi-arid climatic conditions, along with possible anthropogenic influences. Piper trilinear diagram classification shows that mixed CaNaHCO₃ facies predominate in both seasons, followed by NaCl and CaHCO₃ types. A gradual shift toward mixed CaNaHCO₃ and CaHCO₃ facies indicates partial improvement in groundwater quality. Ionic ratio analyses suggest the combined influence of silicate weathering, carbonate dissolution, ion exchange, and evaporation. Multivariate statistical methods further distinguish geogenic controls from anthropogenic impacts such as irrigation return flow and domestic wastewater infiltration. Overall, groundwater quality is marginally suitable for drinking, emphasizing the need for continuous monitoring and sustainable management in this region. This study focusses on 15-year (2008–2022) integrated geochemical and temporal assessment of groundwater quality in Madurai North Taluk, Tamil Nadu. Major ions and TDS frequently exceeded BIS and WHO drinking water limits, with maximum values of TDS (4251 mg/L), Na⁺ (1150 mg/L), Ca²⁺ (512 mg/L), Cl⁻ (1758 mg/L), and HCO₃⁻ (1104 mg/L), indicating progressive groundwater quality deterioration. Gibbs diagram analysis revealed rock–water interaction as the dominant geochemical process (> 60% of samples in both seasons), controlled by prolonged interaction with granite, gneiss, and charnockite lithologies. Piper trilinear diagram classification shows that mixed CaNaHCO₃ facies predominate in both seasons, followed by NaCl and CaHCO₃ types. Ratio plots and multivariate statistical analyses confirmed the combined influence of silicate weathering, carbonate dissolution, ion exchange, and evaporation, with episodic evaporation dominance observed during dry years (2013, 2016, and 2020).