Identifying Groundwater Recharge Areas Most Vulnerable to Nitrate Pollution in the Tébessa Region (NE Algeria): A Statistical and Cartographic Study

Located in northeastern Algeria, the Tébessa region is characterized by a semi-arid climate. Due to the scarcity of surface water resources, groundwater has become the primary source for domestic, agricultural, and industrial use. However, the shallow aquifer system in the area is highly vulnerable to contamination and is increasingly impacted by various pollution phenomena. To investigate the extent and spatial distribution of groundwater pollution, hydrochemical data from about seventy sampling campaigns conducted in 2005, 2006, and 2018 were analyzed. Special attention was given to nitrate (NO₃⁻) concentrations, a key indicator of agricultural and domestic pollution, alongside other chemical tracers such as chloride (Cl⁻), sulfate (SO₄²⁻), and sodium (Na⁺). Multivariate statistical analyses, including Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA), were employed to identify the dominant factors controlling groundwater chemistry and to classify water types and pollution levels across the study area. The results reveal significant spatial variability in groundwater quality, with elevated nitrate levels and other contamination indicators (Na⁺, Cl⁻, SO₄²⁻) particularly concentrated in recharge zones affected by unregulated agricultural practices and wastewater discharge. This situation, suggesting significant anthropogenic influence and highlighting the urgent need for groundwater protection strategies.