<p>Groundwater quality assessment in semi-arid regions is crucial for sustainable water management worldwide, as these areas face increasing pressures from climate change, population growth, and agricultural intensification. Twenty-four groundwater samples were collected during the dry season in the Boulefreis Wadi watershed (northeastern Algeria) to evaluate their suitability for drinking and irrigation, offering novel insights into the interplay of natural and anthropogenic factors in a previously understudied semi-arid system. Field and laboratory analyses were complemented by multivariate statistical tools and a comprehensive set of ten water quality indices. This multi-index approach combining two drinking water indices (GWQI and GPI) and eight irrigation suitability indices (SAR, Na%, PS, PI, RSC, MH, KI, RSBC) constitutes the core methodological novelty of the study. It enables a robust evaluation of groundwater usability, revealing spatial variability and potential risks not captured by single-metric assessments. Principal Component Analysis (PCA) identified major patterns of variability in groundwater chemistry, which were cautiously interpreted as potentially reflecting the influence of natural hydrogeochemical processes (e.g., mineral dissolution, cation exchange, evaporation) and anthropogenic inputs, particularly agricultural activities in the northern and southern parts of the basin. Piper diagrams showed dominant Ca–Mg–Cl and mixed facies linked to regional geology. GWQI and GPI indicated that 54.16% of samples are suitable for drinking, while 41.67% are marginal to doubtful. For irrigation, most indices suggested acceptable conditions, though high sodium and salinity levels in some areas may affect soil permeability and crop yield. This multi-criteria assessment provides a solid baseline for monitoring and highlights the value of broad index application in semi-arid contexts.</p>