Groundwater Suitability for Irrigation in the Hennaya Region, Northwest Algeria: A Hydrochemical and GIS-Based Multi-Criteria Assessment

This study investigated groundwater suitability for irrigation in the Hennaya Irrigated region of Northwest Algeria. The research pursued two primary objectives: first, to establish the hydrochemical origin of the groundwater through comprehensive analyses including hydrochemical parameters, diagrams, and hierarchical clustering; and second, to assess its suitability for irrigation based on key criteria such as the Water Quality Index (WQI), Wilcox, and US Salinity diagrams. The analysis revealed a high level of groundwater suitability for irrigation, as indicated by various indices: Sodium Adsorption Ratio (SAR) values ranged from 1.69 to 2.55 (Excellent), Sodium Percentage (Na%) ranged from 24.22% to 36.98% (Good), and the Residual Sodium Carbonate (RSC) was negative, falling between −8.91 to −1.70 meq/L (Safe). Kelly’s Ratio (KR) ranged from 0.32 to 0.59 (Good), and the Permeability Index (PI) was between 62% and 99% (Moderate). Supported by the Analytic Hierarchy Process (AHP) and spatial analysis, the Water Quality Index (WQI) values ranged from 69.25 to 88.71, categorizing the groundwater in the study area as ‘Good’ quality. While suitable for irrigation, the groundwater showed slight salinity (EC 1247–2010 μS/cm) and alkalinity (pH 7.09–8.02), with elevated total dissolved solids (TDSs) ranging from 990 to 1930 mg/L, approaching the permissible limits for optimal agricultural use. The dominant ion concentrations (Ca2+ > Na+ > Mg2+ > K+; HCO3− > Cl− > SO42− > NO3−) indicate a mixed hydrochemical facies influenced by both water–rock interactions and evaporative processes. Although these findings are promising, they highlight the necessity for preventive measures. Ongoing proactive management and continuous monitoring are essential to ensure the long-term sustainability and protection of groundwater resources in the region.