Hydrochemical Analysis of Groundwater from the Keta Basin, Ghana

Multivariate statistical tools and mineral speciation were used to determine the main controls on the hydrochemistry of groundwater from the Keta Basin, Ghana. Groundwater was also assessed to determine its suitability for irrigation purposes. The study indicates that the hydrochemistry is controlled largely by the intrusion of seawater into the basin. Two hydrochemical facies, the SO 4 -Ca-K- Mg - NO 3 and Cl-Na- HCO 3 facies, have been defined in this study. Saturation indices calculated from mineral speciation indicate that groundwater in the area is generally saturated with respect to gypsum and anhydrite, supersaturated with respect to calcite, aragonite and dolomite, and undersaturated with respect to halite. The extremely high salinity in groundwater from some wells and boreholes in the area is attributed to the role seawater plays in groundwater hydrochemistry in the basin. Chemicals from agricultural activities play a minor role in the hydrochemistry. The sodium adsorption ratio, eltrical conductivity permability indeX, residuals sodium carbonate and sodium percent were the parameters used to assess the suitability of groundwater for irrigation. Groundwater is generally of acceptable quality for irrigation. Over 50% of the samples tested fall within the low sodicity, medium salinity range, which is an acceptable range for irrigation under well drained conditions. Moreover, more than 80% of the samples have permeability indices higher than 70%, which indicates that groundwater in the area will not adversely affect the hydraulic properties of the soils in the Keta Basin area