LAUSR

This study evaluates the suitability of groundwater for drinking and irrigation purposes in the Bhojpur district of Bihar state, based on an analysis of the 15 parameters, namely, pH, electrical conductivity, total dissolved solids, total hardness, calcium content, magnesium content, sodium content, potassium, chloride, sulfate, HCO3−, nitrate, uranium, SiO2, and water quality index (WQI). Ca2+, Mg2+, Na+, and HCO3− dominate the ions in the groundwater, which is of the Ca2+–HCO3− and mixed CaHCO3Na type. As per the elemental concentrations of groundwater, the majority of the samples fall in the permissible range of water quality for drinking and irrigation. According to the Wilcox diagram, about 36.8% of the samples are in the excellent to good category, 47.4% are in the good to permissible category, and 15.8% are in the permissible to doubtful category. Based on the WQI results, the majority of the samples fall under the excellent to good category and are suitable for drinking water purposes. The results indicate that the common samples, which have fair to doubtful quality of water, include SP1, 7, 22, 23, 32, 35, and 37, and are mainly concentrated around the northeast parts of the study area. These samples show generally high values of EC, Clˉ, and Na+K and fall in the fair categories in the Wilcox and Na‐salinity hazard diagrams. The major reasons for the samples in the doubtful category might include growing urbanization, intensive irrigation agriculture, use of fertilizers and pesticides, and industries, which may impact soils, crops, and humans in the long run. The results reveal that the groundwater in the northern parts of the study area is contaminated due to agriculture and other factors, and these areas need to be prioritized in future studies to prevent the degradation of the water quality.