Salinization and anthropogenic pollution are the primary threats to groundwater in the semi-arid regions of southern Tamil Nadu in India. India accounts for 11.6% of the world's agriculture, and also its economy is based on a variety of agricultural activities; especially the Madurai district makes a substantial contribution to meeting the needs of Indian agriculture, particularly in the areas of paddy, pulses, millets, and it makes significant revenues from those activities. The present research evaluated the pre- and post-monsoon groundwater samples from weathered crystalline aquifer across the tourism, mining, and industrial areas of Melur block (Madurai District) to determine the underlying human and biological processes and their suitability for agricultural irrigation. Abundance of cations (Na+ > Ca2+ > Mg2+ > K+) and anions (HCO3- > Cl- > SO42- > NO3- > F-) exhibited hydro-chemical facies of Na+-Cl-, Ca2+-Mg2+-HCO3-, Ca2+-Mg2+-SO42-, and Na+-HCO3- for the pre- and post-monsoon samples. Ninety percent of these specimens in the rock-water interplay dominance field of the Gibbs plot suggested the influence of aquifer lithology on groundwater chemistry, which in turn enhanced the TDS. IWQI values categorized that nearly 25% of samples were on low restriction during both seasons for irrigation accordingly, and the remaining 75% of the samples confirmed on moderate to severe restriction classes, meaning they couldn't apply for irrigational purposes. The geology of the area (e.g., types of rocks and soils), along with mixing and dilution processes, may consistently influence the groundwater quality, leading to similar profiles in both pre- and post-monsoon periods. This comprehensive study provides a hydrogeological database in comparison with WHO (Guidelines for drinking water quality: fourth edition incorporating the first addendum. World Health Organization, Geneva, 2017) guidelines and through the estimations of irrigation indices and IWQI to aid in managing sustainable groundwater resources of Madurai district in south India.