EVALUATION OF AQUIFER POTENTIAL, PROTECTIVITY, AND ADJUSTABLE DEGREE OF VULNERABILITY WITHIN THE COASTAL ENVIRONMENT OF RIVERS STATE, NIGERIA, USING GEO-ELECTRO STRATIGRAPHY

Abstract

Evaluation of aquifer potential, protectivity, and adjustable degree of vulnerability within the coastal environment of Rivers State, Nigeria, were conducted with geo-electrical technology. The vertical electrical soundings were carried out at 30 locations and the 2D electrical resistivity tomography surveys were undertaken at five locations within the study area. Results obtained from these geo-electrical surveys coupled with hydro-geophysical investigations within the area indicated the presence of three to four geo-electric layers: motley topsoil, sandy clay, fine sand, and coarse sand. The geo-stratigraphic data assessed groundwater potentiality, protectivity, and vulnerability to contamination with measures of transverse resistance, hydraulic conductivity, transmissivity, longitudinal conductance, porosity, and permeability. Geo-hydraulic characterization indicated mean aquifer resistivity of 1036.4 Ωm, mean longitudinal conductance of 0.2133 Ω^-1, mean transverse resistance of 55271.2 Ωm², mean hydraulic conductivity of 56.9 m/day, mean transmissivity of 2692.7 m²/day, and mean porosity of 40.55. The results indicated that the region’s groundwater potential ranged from medium to high. Longitudinal conductance values indicated that the aquifer protective capacity ranged from moderate to poor. The study area is generally categorized as extremely vulnerable to surface contamination, i.e., they had weak to poor protectivity to surface pollution. There was good correlation between the hydraulic conductivity and porosity, and between permeability and porosity. The research findings showed that the northeastern axes of the area had greater chances for groundwater potential resulting from its higher values of transmissivity, transverse resistance, and thickness. Locations with sandy lithologies underlying them were noticeably more productive than locations with clayish formations. The findings of this work have contributed to the knowledge of the region’s groundwater potentiality and protectivity. It has also indicated how vulnerable the aquifer system is to contamination. Through the computation of geo-hydraulic characteristics, this work has shown that the aquifer potentiality is higher in the northeast. This work will therefore assist in the improvement of policies on groundwater management/conservation in the region. It will also support in the development of sustainable developmental goals within the region to protect reduction of groundwater resources. Geo-electrical technology was therefore found to be an effective methodology for delineating aquifer potentiality, protectivity, and vulnerability within the vulnerable coastal aquifer system.