Intervening Factors in the Groundwater Salinization Process, Cachoeira River Basin, Northeastern Brazil

Abstract

Hydrogeochemical diagrams and multivariate statistics were applied herein to identify the factors that potentially influence the salinity of water in the crystalline aquifer of the Cachoeira River Basin region, located in the southern portion of the State of Bahia. Data from the hydrogeological database of the Companhia de Engenharia Hídrica e de Saneamento da Bahia (CERB) were applied. The groundwater was predominantly classified as calcium-bicarbonate, with salinity levels ranging from fresh to brackish. The cation that prevails in the region is Ca2+, while carbonate and bicarbonate are the dominant anions. Factor analysis enabled the determination of two factors that explain approximately 93% of the total variance of the data. Hierarchical cluster analysis resulted in five distinct groups based on dissolved ion concentrations. This study indicates that the natural mechanisms that control the chemical composition of groundwater are mainly related to the weathering of rocks and evaporative processes, with the most significant parameters related to the variability of water salinity being Ca2+, Mg2+, K+, Fe (total), and Cl-.