This work examines the physicochemical quality of raw water from dams in western Algeria, focusing on the Mactaa basin (Sarno, Cheurfa, Bohanifia, Ouerzet, Fergoug) and the Tafna basin (Boughrara, Sekkak, Mafrouch, Sidi Abdeli, Beni Behdel). Water sampling campaigns were conducted at the surface water level, assessing parameters such as temperature, pH, electrical conductivity, total suspended solids, oxygen, BOD5, COD, nutrients, salinity, turbidity, heavy metals, and mineral elements. The results indicate that organic matter in these basins originates mainly from natural sources like decomposing vegetation. Metal concentrations in the raw waters of the Mactaa and Tafna basins largely comply with required standards, with treatment processes further reducing metal levels. Standardized principal component analysis revealed varying pollution levels based on proximity to pollution sources and seasonal changes.