This study provides the integrated seasonal assessment of heavy metal contamination in groundwater from the Srivaikundam region, Southern India. Sixty groundwater samples were collected before and after the monsoon, the HPI, HEI, HQ, HI, and CR indices, and GIS-based mapping and multivariate statistics to distinguish geogenic from anthropogenic influences. The pre-monsoon average values (mg/L) were 0.002 (Cd), 0.006 (Pb), 0.006 (As), 0.008 (Cr), 0.012 (Ni), 0.031 (Cu), 0.017 (Mn), 0.141 (Zn), and 0.010 (Fe). Post-monsoon levels dropped to 0.001 (Cd), 0.005 (Pb), 0.005 (As), 0.008 (Cr), 0.010 (Ni), 0.022 (Cu), 0.014 (Mn), 0.116 (Zn), and 0.008 (Fe). All samples met the WHO (WHO (2017) Guidelines for drinking water quality: Fourth edition incorporating the first addendum. World health organization, Geneva.) drinking water guidelines, except for one pre-monsoon sample, when Cd levels surpassed the 0.003 mg/L limit. The Heavy Metal Pollution Index (HPI) varied from 27.74 to 122.33 in pre-monsoon samples and 27.73 to 92.32 in post-monsoon samples. The Heavy Metal Evaluation Index (HEI) values varied from 0.52 to 2.33 and 0.48 to 1.76, respectively. During the pre-monsoon period, health risk analysis revealed that 16% of samples were low risk (HI < 0.5), 52% intermediate (HI = 0.5-1.0), and 32% high risk (HI > 1.0). The post-monsoon values improved, with 25% low risk, 50% moderate, and 25% high risk. Non-carcinogenic hazards (HQ > 1) were found in 26.67% of pre-monsoon and 15.0% of post-monsoon samples. Carcinogenic risk levels were within tolerable ranges (CR < 1 x 10(-4)). The novelty of this work lies in its combined use of pollution indices, health risk models, and multivariate statistics to demonstrate how monsoonal recharge and anthropogenic inputs jointly control groundwater quality. The findings highlight a scientific basis for targeted groundwater monitoring, safe drinking water management, and long-term policy strategies in the vulnerable semi-arid river region of South India.