Physicochemical Quality and Hydrochemical Facies of Groundwater in Kolokuma Opokuma Local Government Area, Bayelsa State, Nigeria

Groundwater serves as the principal source of domestic water in many Niger Delta communities, making its quality assessment essential for public health protection. This study evaluated the physicochemical properties, major ions, hydrochemical facies, and potability of groundwater from seventeen boreholes in kolokuma Opokuma Local Government Area, Bayelsa State, Nigeria. Groundwater samples were analyzed in triplicate and results compared with World Health Organization (WHO) drinking-water guidelines. pH values ranged from 5.57 ± 0.05 to 6.87 ± 0.06, indicating slightly acidic to near-neutral conditions. Electrical conductivity (72.61 ± 1.80–378.00 ± 6.80 µS/cm) and total dissolved solids (36.30 ± 1.00–189.00 ± 4.50 mg/L) classified the groundwater as fresh. Nitrate concentrations were low (0.11–1.68 mg/L), while total hardness ranged from 42.0 ± 1.9 to 140.0 ± 3.9 mg/L, indicating soft to moderately hard water. Iron concentrations ranged from 0.014 ± 0.002 to 0.300 ± 0.020 mg/L, reaching the WHO guideline limit in one borehole. Piper trilinear analysis classified all samples as Ca–SO₄ hydrochemical facies, reflecting dominant geogenic control through mineral dissolution. One-way ANOVA revealed significant spatial variation (p < 0.001) for most parameters. Overall, groundwater in the study area is suitable for domestic use, with minor treatment required to correct acidity and localized iron enrichment.