HydrochemicalFacies in Parts of the Nigerian Basement Complex

 Water analyses usually involve large amounts of data that require sorting to aid in interpretation. One method that could be used is the hydrochemical facies diagrams. The hydrochemical facies of groundwater from four drainage basins of the Nigerian basement complex, Ife, Asa, Shika, and Kan Gimi, are evaluated using trilinear and Stiff diagrams similar to methods used in lithofacies and geochemical studies. The hydrochemical facies for the basins studied are influenced, aside from the lithology, by the rainfall and their proximity to the sea. In general, no single cation–anion pair exceeds 50%, hence an appreciable percentage of the groundwater in the study areas is of the nondominant type. Within the overburden aquifer of the basement complex, with limited regional flow, a rainfall of about 1150 mm per annum is arbitrarily set as the boundary between alkaline and saline groundwater.