Introduction The research investigates the hydrogeochemical characteristics of the Complex Terminal aquifer in Guerrara, Algeria, utilizing sophisticated statistical techniques to unravel groundwater composition and quality dynamics. Objectives The primary objectives of the study were to analyze the hydrochemical composition, identify geochemical water facies, evaluate water quality for consumption and irrigation, and determine the sources of water mineralization. Results The data obtained revealed water samples with a slightly alkaline pH and high mineral concentrations. The order of decreasing ion concentration was identified as: Sulfate (SO4), Chloride (Cl), Sodium (Na), Calcium (Ca), Bicarbonate (HCO3), Magnesium (Mg), Nitrate (NO3), and Potassium (K). Geographical Information System (GIS) was utilized to visualize spatial parameter distribution. Hierarchical Component Analysis (HCA) identified four distinct geochemical water facies: SO4-Na- Ca, SO4-Na-Cl, SO4 with no dominant cation, and SO4-Cl-Na-Ca. The correlation coefficient showed electrical conductivity highly correlated with Sodium (r = 0.951), and a negative correlation (r = −0.235) between pH and nitrate. Principal Component Analysis categorized water parameters into three principal components representing 72.66% of the overall variance. The analysis revealed that the primary sources of water mineralization are the dissolution of evaporitic and carbonate rocks, along with anthropogenic activities. The Saturation Index indicated water samples were supersaturated with calcite and dolomite, while being undersaturated with gypsum, anhydrite, and aragonite.