Abstract: As one of the major strategic projects in China’s overall water resource allocation framework,the Eastern Route of the South-to-North Water Diversion (SNWD) Project has undergone hydrodynamic changes before and after water diversion,which may increase the susceptibility of its water and sediments to contamination by heavy metals and other pollutants.Therefore,this study focused on the Phase I Eastern Route Project,systematically analyzing the temporal and spatial distribution characteristics and influencing factors of six heavy metals (Cr,Cu,Ni,Pb,V,and Zn) in water and sediments before and after water diversion.The geo-accumulation index (I_geo) and potential ecological risk index (RI) were used to determine the ecological risk levels of heavy metals in sediments.The results showed that the water diversion process affected the temporal and spatial distribution and ecological risks of heavy metals;however,the concentrations of heavy metals in both water and sediments did not exceed the relevant environmental quality standards or the background values of riverine sediments in China.The influence of water diversion on the distribution of heavy metals in water was greater than that in sediments,and heavy metals in water showed significant correlations with nitrogen.In sediments,except for Zn,Ni,and Cr at a few sites that were affected by anthropogenic activities,heavy metals were mainly controlled by natural factors.The I_geo and RI results indicated that the ecological risks of heavy metals in sediments of the East Route Project were at a non-polluted level,and the water diversion process contributed to the reduction of heavy metal ecological risks.