RESUMEN
A total of 148 groundwater samples were collected from bore wells from Thirumanimuttar sub-basin for two seasons to identify major geochemical process activated to alter groundwater chemistry. The study revealed relationships with the lithology and anthropogenig process. Groundwater in the region was domnated by Na- Ca - Mg and Cl and HCO[3] types. The [Ca + Mg] Versus TZ[+] plot for both seasons reveals higher Ca and Mg due to leaching due to silicate mineral weathering from aquifer matrix of the study area. The plot for [Na+K] versus TZ[+] indicates weathering process of both alkali and alkali earth from feldspars along with additional sources like contribution from alkali/saline soil and residence time. Saturation index of silicate, carbonate and fluoride minerals indicates oversaturation and equilibrium state and sulfate minerals were at undersaturated state during both the seasons. Lithology and anthropogenic activity plays a significant role in controlling groundwater chemistry of the study area