Scientific African (Sep 2021)
Mapping a spatial salinity flow from seawater to groundwater using electrical resistivity topography techniques
Abstract
In this work, the spatial salinity flow of surface water (ocean) into coastal groundwater (wells and boreholes water) in Okun-Ajah and its environ is reported using Electrical Resistivity Tomography (ERT) to show the interaction of surface water with the aquifer of the adjoining coastal communities. The ERT data were supported with measurements of in situ hydro-physical parameters for confirmation. Eight (8) ERT traverses were established in the area, and nineteen (19) shallow wells, eight (8) deep wells (boreholes) and eight (8) surface water samples were analysed in situ in the work. The ERT model inversion show underground aquifer with very low resistivity all through the profiles established parallel to the coast while the very low resistivity region thin out under the traverses established perpendicular or tangential to the coast. Hydro-physical parameters such as electrical conductivity (EC), total dissolved solids (TDS). pH and temperature were also measured for all categories of water sampled (wells, boreholes and ocean). The results show that the concentrations of EC and TDS, agents of salinity, reduce away from the ocean, while aquifers with clear proximity to the ocean show elevated values. The correlation of all data clearly indicated the underground flow path of the ocean into the coastal aquifers. The integrated techniques have proven to be veritable tools to map saline water intrusion into coastal aquifers.
