<p>Groundwater is essential in the semi-arid areas of South India, where unpredictable rainfall and limited surface water, increase reliance on underground water for drinking and farming. In the industrially active Sivakasi area, worries about groundwater pollution have grown due to rising human activities, such as fertilizer application and industrial wastes. This research seeks to assess the quality of groundwater for drinking and irrigation, concentrating on spatial differences, contamination risks, and health effects, by employing combined hydrogeochemical and geospatial methods. A total of 77 groundwater samples were analyzed for physicochemical parameters such as pH, electrical conductivity (EC), total dissolved solids (TDS), major ions (Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃^-, Cl^-, SO₄^2-), and key contaminants (fluoride and nitrate). The Piper diagram revealed that 70% of samples belong to the mixed Ca–Mg–Cl water type. Fluoride levels exceeded World Health Organization (World Health Organization-WHO <CitationRef CitationID="CR90">2017</CitationRef>) limits in 24% of the samples, rendering 140.16 km² unsuitable for drinking, while nitrate levels above 45&#xa0;mg/l affected 36.4% of samples, impacting 250.93 km². A Water Quality Index (WQI) map classified 140.49 km² as having very poor water quality, and 422.29 km² as not suitable for human consumption. Conversely, irrigation assessments using USSL, Wilcox, and Doneen diagrams, along with Sodium adsorption ratio (SAR), Residual sodium carbonate (RSC), Kellys Index (KI), Sodium Percentage (Na%), and Magnesium Hazard Ration (MHR) indices, indicated that most groundwater sources were suitable for agricultural use. However, health risk assessments revealed significant non-carcinogenic risks, especially among infants, due to excessive fluoride and nitrate exposure. GIS-based mapping aids in groundwater management, ensuring drinking water safety and irrigation suitability.</p>