<p>The primary goal of any water quality monitoring study is to evaluate the condition of water for specific uses. The water quality of the Sabi river basin in Rajasthan, India, a tributary of Yamuna River, was assessed for drinking purpose using the Water Quality Index (WQI) method integrated with Geographic Information System (GIS) technology. The research involved collecting eighty-three groundwater samples from various locations within the Sabi river basin, during the pre- and post-monsoon seasons over two years, 2022-23 and 2023-24. The study focused on analysing these samples for multiple parameters including pH, TDS, EC, Mg²⁺, Ca²⁺, Na⁺, K⁺, Cl⁻, SO₄²⁻, CO₃⁻, HCO₃⁻, NO₃⁻, and F⁻. The measured parameters were compared against the Bureau of Indian Standards (BIS) for water quality. Results showed that the groundwater in the Sabi basin was slightly alkaline. In the pre-monsoon period, concentrations of Ca²⁺ and NO₃⁻ exceeded recommended limits, while TDS, EC, HCO₃⁻, Mg²⁺, and K⁺ levels were above BIS standards in both seasons. Conversely, pH, Na⁺, Cl⁻, SO₄²⁻, CO₃⁻, and F⁻ remained within acceptable limits throughout both seasons for drinking purposes. Further, chemical characterization was conducted using Piper and Gibbs diagrams. The Piper diagram revealed a mixed Ca²⁺-Mg²⁺-Cl⁻ hydrochemical facies, while Gibbs plots suggested that evaporation influenced groundwater chemistry in the pre-monsoon, and rock-water interaction was dominant in post-monsoon. Additionally, GIS-based WQI maps indicated a higher prevalence of poor water quality areas during the pre-monsoon season (81.57%) compared to the post-monsoon season (66.16%). The study will help policymakers, local communities, and environmentalists to develop effective strategies for managing and conserving water resources. </p>