Interpretation of Groundwater Quality Using Statistical Techniques in Federal University, Otuoke and Environs, Bayelsa State, Nigeria

This study aims at assessing and interpreting groundwater quality using statistical techniques in Otuoke and environs, Bayelsa State, Nigeria. Fourteen (14) groundwater samples were collected in the rainy season and analyzed for their physico-chemical and heavy metal contents. Heavy metals were analyzed using Atomic Adsorption Spectrometer. Assessment for drinking purposes revealed that the water is predominantly acidic, with iron and manganese contents exceeding regulatory guidelines in most locations. All other parameters were within WHO and NSDWQ regulatory limits for safe potable water. Water Quality Index revealed that over 73% of the groundwater in the area (11 samples) had good to excellent quality; while the remaining 27% of the groundwater (3 samples) have poor to unsuitable quality for consumption. Assessment of water quality for irrigation purposes was achieved using Sodium Adsorption Ratio (SAR), Potential Salinity (PS), Permeability Index (PI), Sodium percentage (Na%), Kelly’s ratio (KR), and Magnesium Adsorption Ratio (MAR). On average SAR (4.19), PI (68.51%), MAR (37.45%) and PS (0.77) revealed excellent water quality, whereas Na% (66.46%) revealed doubtful water quality while KR (2.00) revealed unsuitable water quality. Using Piper and Stiff diagrams, hydrochemical facies defined from groundwater in the area includes; Na+K – Cl facies; Na+K - Mg – Cl facies; and Na+K - Ca – Cl facies. Gibb’s diagrams revealed that the dominant control on the hydrochemical facies and overall groundwater quality in the area has been attributed to precipitation and chemical weathering of subsurface rocks. Various ionic ratios including Mg/Ca (0.642), HCO3ˉ/Cl (0.040), (Na+K)/Cl (7.026) and Cation Exchange Values (-6.026) revealed low salt inland origin with respect to provenance. Pearson correlation matrices showed both positive and negative inter-relationships between the physico-chemical and heavy metals in groundwater within the study area. This study has proven the effective use of water quality index as a tool for defining the overall quality of water in Otuoke and its environs, along with hotspots that needs immediate attention. The results could also serve as a decision making tool that will aid in establishment of treatment facilities to improve the quality of water in the study area.