Water scarcity, exacerbated by unequal distribution and environmental fragility, presents a substantial obstacle in Algeria. Despite concerted efforts, shortages continue to exist, requiring immediate action. This study aims to evaluate the influence of human activities, climatic factors and the leaching of minerals from geological formations on the water quality of Hammam Boughrara dam (NW Algeria), and to determine whether this water is suitable for human consumption and irrigation. Monthly data from 2005 to 2023 were analyzed using the trend method, Principal Component Analysis (PCA), and generalized Additive Models (GAMs). GAMs revealed significant non-linear correlations: rainfall influenced EC, DO, and Cl- through dilution; water volume stabilized turbidity, organic pollutants, and oxygenation through dilution and mixing; and evaporation concentrated nutrients like NH4+ and NO3-. The Piper diagram revealed dominant sodium-chloride facies, with a temporal shift toward mixed water types. The Water Quality Index (WQI) was used to determine whether this water is suitable for consumption and irrigation. The trend method indicated that most chemical parameters originated from industrial and agricultural activities, with a few resulting from water-rock alteration. The PCA shows that mineral dissolution and industrial emissions represent 34.9%, while anthropogenic and agricultural contamination account for 21.9%. The WQI confirms that the water is unsuitable for drinking without treatment but suitable for irrigation in soils with moderate to high permeability.