Hydrogeochemical Processes Governing Groundwater Quality in a Semi-Arid Basin, Northeastern Algeria

Abstract

This study addresses the hydrogeochemical assessment of alluvial aquifers in a semi-arid region, where groundwater constitutes a critical resource for drinking supply and irrigated agriculture but is increasingly threatened by salinization and geogenic constraints. It investigates the hydrogeochemical characteristics and practical usability of groundwater from the Quaternary aquifer of the Bousselam Upstream River basin (BUR), northeastern Algeria. Forty-two groundwater samples were collected from fourteen wells during three monitoring campaigns conducted in 2020, 2022, and 2024 to capture spatial variability and short-term temporal evolution. Physicochemical parameters and major ions were analyzed following APHA standard methods, and hydrochemical facies were identified using Piper, Schoeller, Wilcox, and Riverside diagrams. Groundwater is mildly alkaline and moderately mineralized (EC:1154–1632 μS/cm), reflecting dominant water-rock interactions with limited anthropogenic influence. The prevailing Ca-Mg-SO4-Cl and Ca-HCO₃ facies are controlled by carbonate and evaporite dissolution and ion-exchange processes. Total hardness values indicate predominantly hard to very hard water. Water Quality Index values (25–75) range from good to poor, while irrigation assessments classify most samples as S1C3, indicating low sodium hazard but elevated salinity. Beyond academic characterization, the results highlight practical constraints on long-term use and support the need for targeted management strategies to sustain groundwater use for drinking and irrigation.