Investigation of the quality of groundwater and its appropriateness for drinking and agriculture in Gaya district, Bihar, India

This investigation evaluates groundwater quality in Gaya District, Bihar, with an emphasis on its suitability for drinking and agriculture with respect to nitrate (NO3−) and fluoride (F−). Twenty-one groundwater samples data were retrieved during the dry season, and analyzed for 16 hydrochemical parameters. Evaluation techniques included water quality index (WQI), correlation matrix, principal component analysis (PCA), and hydrochemical diagrams. Groundwater is found hard to very hard, dominated by HCO3 type and mixed Ca-Mg-HCO3 facies. Fluoride concentration (0.9–1.6 mg/L) exceeded the World Health Organization (WHO) limit (1.5 mg/L) at one site (SP3). Uranium levels (0.0005–0.0525 mg/L) exceeded the permissible limit (0.03 mg/L) by 1.07 to 1.75 times higher at certain locations. WQI classified 33.3% of samples as excellent and 4.8% as unsafe. PCA extracted three factors explaining 81.32% of variance, linked to salinity and hardness. Groundwater is mostly suitable for irrigation, though high magnesium absorption ratio (MAR) and potential salinity (PS) indicate local salinity issues.