Integrated Hydrochemical Assessment of Groundwater Quality in El-Mahmel Plain, Algeria: A Hydrochemical, Water Quality Index and Multivariate Statistical Approach

Abstract

This study investigates groundwater quality in the El-Mahmel plain, northeastern Algeria, using hydrogeochemical analysis, multivariate statistics, and the Water Quality Index (WQI). In total, 13 parameters were investigated in this context: pH, electrical conductivity, TDS, TH, and main ions (K⁺, Na⁺, Ca²⁺, Mg²⁺, Cl⁻, HCO₃⁻, SO₄²⁻, PO₄³⁻, and NO₃⁻) in sixty water samples. The results show that groundwater salinization is caused by natural processes, including water–rock interactions and evaporitic rock dissolution (gypsum, halite, etc.), as indicated by high TDS and EC values. Cation exchange processes, especially in the vicinity of the Sabkha environment, further change the chemistry of groundwater by enriching sodium and depleting calcium and magnesium. Three groundwater facies were identified: Ca–Cl (41%), Na-Cl (35%) and mixed Ca–Mg–Cl (24%), with calcic-chloride facies dominating. WQI classification showed 66% of samples as poor quality, 22% as good quality (in the central area), and 12% of samples have very poor quality. Multivariate statistical analysis confirmed the influence of geogenic and anthropogenic factors, noting significant correlations between salinity (TDS), and Cl⁻, SO₄²⁻, Na⁺ and WQI. Five water types were identified, reflecting varying natural and anthropogenic impacts. The study underscores the need for sustainable groundwater management, recommending wastewater treatment for recharge and improved agricultural practices to reduce contamination. These findings provide a basis for protecting the El-Mahmel aquifer system.