The aim of this study was to assess a spatial and temporal variations in water quality of the Euphrates River flowing through Iraqi lands, with two approaches: the use of water quality index (WQI) and a principal component analysis (PCA). In the studied section of the river the global water quality WQI was 63.09 (classified as medium – slightly polluted), this value denotes that Euphrates water requires
treatment for drinking, no treatment necessary for most industries and crop uses and suitable for most fish and not recommended for sensitive one. PCA results indicate that three factors for river water explain 92.95% of the total variance. Varifactors obtained from factor analysis for water quality variations indicate that factors responsible for water quality variations are mainly related to soil leaching and runoff process, organic pollution from municipal effluents, pH and