Assessing the Drinking Water Quality Index in Arid Areas: An Analysis of the El Hadjeb Region in Biskra, Southeastern Algeria.

Investigating the hydrogeochemical processes and regional variations in groundwater quality within the Lower Eocene aquifer of the El Hadjeb region in southeastern Algeria is the aim of this study. The groundwater samples are tested for electrical conductivity (EC), pH, temperature (T), total dissolved solids (TDS), and major ionic elements like Na⁺, K⁺, Ca²⁺, Mg²⁺, CO₃²⁻, HCO₃⁻, Cl⁻, and SO₄²⁻. In semi-arid and arid regions, the aquifer is a very important source of water. The findings indicate that sodium chloride (Na-Cl) is the predominant hydrochemical facies of the groundwater with evaporite mineral undersaturation and a small amount of dolomite precipitation. The modal Gibbs diagrams suggest that the main geochemical regulators are evaporation and rock-water interactions. The samples examined had Water Quality Index (WQI) values between 87.26 and 153. 33.33% of the samples fall into the "good" category and 66.66% into the "poor" category. High WQI values, which indicate declining water quality, are associated with increases in SO₄²⁻, K⁺, Na⁺, Ca²⁺, Mg²⁺, HCO₃⁻, Cl⁻, and TDS. These results demonstrate how important effective groundwater management is to maintaining the sustainability of this fragile aquifer.