In this study, spatio-temporal variation of surface water quality were assessed in Talar River, located in north of Iran based on 12 parameters at six stations during 2003-2011 using one-way ANOVA, principal component analysis (PCA) and cluster analysis (CA) techniques. The results of one-way ANOVA showed that temporal and spatial variations influences on water quality parameters siginificantly as decline in river water quality. Based on this analysis, Khatirkuh-Doab and Pol Shahpoor stations had the highest and the lowest amounts of almost all of the water quality parameters, respectively. The results of principal component analysis indicated a close relationship between the anions and cations, concentration of soluble salts, electric conductivity and total hardness in all years of study and at all stations. Moreover, PH and HCO3 parameters in 2005-2006, 2007-2008, 2008-2009 and 2010-2011 and at Kiakola, Pol Shahpour and Shirgah-Talar stations; Cl, Na and SAR parameters at Paland station; Total Hardness and SO4 parameters at Kiakola station and HCO3 and PH parameters at Kiakola, Pol Shahpour and Shirgah-Talar stations had a close relationship with each other. Mg parameter at Pol Shahpour station, SO4 parameter at Khatirkuh-Doab station, HCO3 parameter at Pol Sefied-Talar and Khatirkuh-Doab stations, PH parameter at Pol Sefid-Talar, Khtirkuh-Doab, and Palnd stations had a significant presence in 2003-2004, 2004-2005, and 2009-2010. Cluster analysis results also showed that Kiakola and Shirgah - Talar stations are placed in the first cluster, Pol Shahpour and Paland stations are set in the second cluster, Khatirkuh-Doab and Pol Sefied-Talar stations are located in the third and fourth clusters, respectively.
