Hydrogeochemical characterization and seasonal variability of groundwater in the Seriana plain (Northeastern Algeria): Implications for drinking suitability

Recent advances in groundwater research have highlighted the importance of multidisciplinary approaches for achieving a comprehensive understanding of groundwater quality and supporting more effective water-resource management. To address this need, this study provides an integrated hydrogeochemical assessment of a dual karst-alluvial aquifer in the Seriana–Zana–Aïn Djasser–El Hassi region in northeastern Algeria, where groundwater represents the primary source of domestic and agricultural supply, yet its quality remains vulnerable to climatic variability and increasing anthropogenic pressure. The approach combines physicochemical analyses, Water Quality Index (WQI), and multivariate statistics (PCA and HCA), using samples collected during the dry (June 2019) and wet (December 2019) seasons. The results show marked seasonal contrasts in groundwater quality: more than half of the dry-season samples fall within poor to very poor WQI classes, while wet-season recharge produces a clear dilution effect, shifting most samples to good or excellent quality. Spatially, lower-quality waters are concentrated in the eastern sector of the basin, reflecting persistent environmental pressure. Hydrochemical facies identified using Piper, Durov, Chadha, and Stiff diagrams indicate the predominance of Ca–Mg–HCO3 and mixed Ca–Mg–SO4 types, highlighting the influence of carbonate and evaporite dissolution, cation exchange, and groundwater mixing. PCA reveals that PC1 (38.1% of total variance) is dominated by Ca2+, Mg2+ and Na+, and is strongly associated with WQI, confirming the major role of geogenic processes. PC2 accounts for 23.5% of the total variance, mainly distinguishing salinisation or evaporite dissolution processes. Lastly, PC3 (14.1% of total variance) differentiates the two sampling periods. HCA delineates five hydrochemical clusters, mostly stable across seasons, while isolating samples affected by salinisation or evaporite dissolution. Nitrate levels remain moderate but point to localised agricultural and domestic contributions. Overall, the combined evidence demonstrates that groundwater chemistry in the Seriana Plain is primarily governed by natural water–rock interactions, although seasonal variations and anthropogenic activities exert measurable impacts. These findings provide a robust scientific basis for guiding in-depth analyses on recharge processes and potential contamination sources as well as planning focused groundwater monitoring activities and protection strategies.