Multidisciplinary approach to understand the salinization of fractured crystalline aquifers in semi-arid region

Abstract

In semi-arid areas, groundwater (GW) represents the most reliable resource for water supply. In the semi-arid region of Ceará (Northeastern Brazil), GW of the crystalline fractured aquifers has a salinity higher than expected in this type of environment. This study implemented a multidisciplinary approach based on hydrodynamic (piezometric) and hydrogeochemical (18O, 2H, 3H, 14C, CFC, SF6, Electrical Conductivity, major ions) data to understand the salinization processes. Results demonstrate that GW is generally recent and recharged by meteoric waters mainly through indirect infiltration from evaporated surface water. The study suggests that GW, originally bicarbonated, becomes progressively enriched in chloride due to the dissolution and leaching of salts, during the wet season, which come from meteoric inputs and have precipitated in the unsaturated zone and pond sediments during dryer periods.