<p>An integrated hydrochemical, statistical, and geospatial approach was adopted in the present study to evaluate the groundwater quality of the Mangura Nala watershed in the state of Bihar, India. A total of 154 groundwater samples were collected during two seasons (77 samples from each season) and analysed for various physico-chemical parameters, major ions, and fluoride concentrations. The groundwater of the area was characterised by Ca-Mg-HCO₃ and Ca-Mg-Cl water types during both seasons. The estimation of saturation states of the aqueous minerals and chloro-alkaline indices suggested dominant impacts of sediment–water interaction and ion exchange processes in the groundwater. The ANOVA test depicted seasonal changes in groundwater quality, while the multivariate analyses, including principal component analysis and cluster analysis, clearly recognised potential water quality parameters deteriorating the groundwater quality in the study area. Around 30–45% of groundwater samples were found to have higher water quality indices, making them unsuitable for drinking purposes, while the unsuitability of groundwater for irrigation purposes was identified at a few locations, as observed from various parameters such as %Na, magnesium hazard, soluble percentage, potential soil salinity, permeability index, etc. From the geospatial analyses, it was found that the samples unsuitable for drinking and irrigation purposes were mostly located in the central, southern, and northern parts of the study area. Higher concentrations of major ions like Na and Mg, along with F and NO_3, were mainly responsible for the higher values of water quality indices and irrigational parameters. The integrated hydrochemical and statistical approach provides an overall characterization of groundwater quality in the study area, which will act as baseline data for future studies. Further, the study has traced poor groundwater zones, which should be avoided for direct consumption of water for drinking purposes.</p>