Characterization of water chemistry in some communities of the Lower Tano river basin, Ghana, West Africa

The chemistry of surface water and groundwater in some communities of the Lower Tano river basin, which is a coastal region of Ghana, has been characterized. Based on the obtained analytical results, 80% of the surface water (rivers), 100% of the hand dug wells and 96% of the boreholes in the study area are generally fresh and soft. Silicate weathering is the main hydrogeochemical processes contributing to the Na+ ions and HCO3− ions in the groundwater of the basin. Gibbs diagram used to identify the mechanisms controlling the water chemistry of the basin reveals that rock weathering resulting from silicate and carbonate minerals controls majority of the surface water and groundwater chemistry in the basin. Piper trilinear plots and Chadha’s diagram, used in this study, indicate that ion exchange processes, reverse ion exchange and rock weathering are the main hydrogeochemical processes controlling the groundwater resources in the basin. Stable isotopic (δ2H and δ18O) composition measurements obtained from the study indicate that 30% of the surface water (rivers and lagoon) are less depleted and subjected to evaporation, while the remaining 70% is highly depleted with negligible to no evaporation. Also, the groundwater in the basin is likely recharged by direct infiltration of rainfall from the local rains of the basin together with other sources.