Hydrochemical Investigation of Saline Water Intrusion into Aquifers in Part of Eastern Dahomey Basin, Southwestern Nigeria

Abstract

This study is a major attempt at delineating presence and lateral extent of saline water intrusions into aquifers at the easternmost part of Dahomey basin which falls essentially in the sedimentary terrain of Ondo State of Nigeria. 61 water samples were collected from hand dug wells, shallow boreholes, and ponds across the study area and analyzed for relevant parameters such as pH, conductivity, total hardness, calcium hardness, magnesium hardness, total dissolved solids, alkalinity and concentrations of the following anions and cations; chloride, calcium, Sulphate, bicarbonate, magnesium and sodium. Equivalent salinity was calculated from the water sample analysis results. The hydrochemical analysis results reveals possible saline water intrusion in the coastal area, especially the southeastern part and Agbabu in the north central part of the study area as evident from high concentration values of chloride (372 - 1500 mg/l), alkalinity (105 - 330 mg/l), equivalent salinity (135 - 2808 mg/l), total dissolved solid (181 - 1005 mg/l), high pH values (4.4 - 8.6 pH) and conductivity values (541 - 1500 µs/cm).

Keywords: Saline water intrusion, saline-freshwater boundary, hydrochemical and equivalent salinity.