APPLICATION OF ELECTRICAL RESISTIVITY METHOD TO INVESTIGATE SALTWATER INSTRUSTION IN OTATUBU COMMUNITY OGBIA LGA, BAYELSA STATE, NIGERIA

ABSTRACT Electrical resistivity method is a geophysical investigation technique used in the exploration of natural resources and in resolving environmental related challenges. Geo-electrical resistivity survey was carried out in Otatubu Community and its Environs, Ogbia Local Government Area, Bayelsa State, Nigeria to identify saltwater intrusion and to map out the saltwater plume. The Schlumberger configuration was used for the data acquisition with AB = 200m. A total of Five (5) Vertical Electrical Sounding (VES) station were established within the study area. The quantitative interpretation of the 1-D VES result showed a series of layer thicknesses, depths and associated resistivity values were defined that is consistent with the VES responses of each location. Saline intrusion was delineated within the aquifer zone of four (4) VES station (VES 1, 2, 3 and 4) in Otatubu community with contrast to low resistivity which ranges from 111Ωm to 235Ωm, while at VES 5 resistivity value were notably higher within same depth range. VES 5 which was situated about 10km away from Otatubu showed a resistivity value of 644Ωm within the aquiferous zone. The outcome of the study agrees with field observation of saline water within boreholes in Otatubu which are absent in wells about 10km away. It was also verified that the bulk resistivity values is not only a product of the matrix composition but is greatly influenced by the chemical composition of the pore fluid, which in this case is influenced by more conductive saline water. It is important that boreholes in Otatubu communities that have encountered saline water should be prevented from further use until treatment for salt water intrusions are conducted. A comprehensive groundwater exploitation plan should be developed by relevant authorities as to improve the plight of the Otatubu community and its environs.