HYDRAULIC CHARACTERIZATION AND QUALITY RATING COMPUTATION OF GROUNDWATER PARAMETERS IN THE DEEPER AQUIFER OF OGONILAND, SOUTHERN NIGERIA

Groundwater is a critical source of freshwater in Ogoniland, Southern Nigeria, where oil exploration, gas flaring, urbanization, and population growth pose potential risks to aquifer quality. This study, Hydraulic Characterization and Quality Rating Computation of Groundwater Parameters in the Deeper Aquifer of Ogoniland, Southern Nigeria, aimed to evaluate the hydraulic properties and water quality of both upper and deeper aquifers across ten representative communities: Bodo, Beeri, Borobara, Barayira, Eteo, K-Dere, Kpean, Uegwere, Korokoro, and Onne. A mixed-method approach was employed, combining field measurements of hydraulic parameters such as static water level, transmissivity, hydraulic conductivity, and storativity with multi-depth water sampling for physicochemical, major ion, trace metal, and microbiological analyses. Weighted sub-indices and the Water Quality Index (WQI) were computed to assess spatial variations and suitability for domestic, agricultural, and industrial uses. Results for the deeper aquifer showed substantial spatial variability in WQI, ranging from 11.37 at Barayira, indicating excellent water quality, to 148.65 at Beeri, classified as very poor. Major ions such as sodium, chloride, calcium, and magnesium generally exhibited low sub-index values, reflecting relatively fresh groundwater, while iron showed significant heterogeneity with extremely high concentrations at Beeri and Onne, suggesting localized geogenic enrichment or anthropogenic influence. Nitrate levels remained very low across all sites, indicating minimal impact from agricultural runoff or sewage. Comparatively, the upper aquifer displayed slightly higher WQI values in shallow zones, with poorer quality observed at Onne, highlighting the greater vulnerability of shallow aquifers to human activities. Hydraulic characterization revealed semi-confined aquifer conditions with variable transmissivity, storativity, and hydraulic conductivity, which influence recharge, water availability, and contaminant migration. Overall, the findings indicate that Ogoniland’s deeper aquifer is predominantly of good to excellent quality, while localized hotspots require targeted monitoring and management. Recommendations include routine water quality monitoring, protection of recharge zones, proper industrial and waste management to minimize contamination, and remedial interventions in areas with poor WQI to ensure safe and reliable groundwater resources for domestic, agricultural, and industrial use.