Groundwater quality beyond potability: decoding the hydrogeochemical signatures using spatial and statistical methods in regions of Dindigul District, Tamil Nadu

Groundwater in the Jivalsaragu area of Dindigul district, Tamil Nadu, is essential for domestic and agricultural purposes. However, contamination from the usage of excessive fertilizers and natural weathering of charnockite & migmatite have significantly deteriorated the groundwater quality in the study area, highlighting the need for a comprehensive assessment. The results reveal that the groundwater is alkaline and hard, primarily due to elevated levels of Ca2+, Mg2+ and HCO3−, which reduce its suitability for domestic purposes. Hydrogeochemical analysis, irrigation suitability indices, and statistical methods such as correlation and principal component analysis were applied. Significant pollution was observed, with 95% magnesium, 85% sulphate, and 60% calcium above acceptable limits due to fertilizer leaching and mineral dissolution. According to Gibbs, evaporation is the fundamental driver of groundwater chemistry, and Correlation shows significant interaction among parameters, such as strong positive trends between electrical conductivity and total dissolved solids. Principal Component Analysis (PCA1-4) revealed that mineral concentration and salinity are the most critical factors influencing groundwater quality. Wilcox indicates that 50% of the samples were unsuitable due to sodium and chloride enrichment. Water Quality Index (WQI) implies that 50% of water is extremely poor, 25% very poor, and 20% unsuitable due to rock-weathering and anthropogenic inputs. The irrigation indices (SAR, KR, SSP, and MAR) reveal that 70% of the water can be used for irrigation after treatment, while the rest is inappropriate. The findings conclude that the study area requires groundwater management steps such as treatment, aquifer recharge systems and sustainable irrigation.