Awash River is considered as most important river for the surrounding community, but it is vulnerable to anthropogenic activities. Thus, the present study was investigated about the pollution status of Cr, Cu, Mn, Cd, and Pb and their ecological risk in aquatic system of Awash River. Water and sediment samples were collected from selected sampling sites of the river and its tributaries and samples were analyzed. The results showed that concentrations of Cr, Cd, Cu, Mn and Pb in the water samples were higher than standards set by WHO and USEPA in some sites of the upper basin of the river. Heavy metals contamination in the sediments were evaluated by applying USEPA sediment quality Guidelines and various indexes such as Enrichment factor, Geoaccumulation index, Contamination factor , Degree of contamination, Ecological risk factor and Potential ecological risk index. The results revealed that the values of each indexes was high in the upper basin sampling sites of the river and the amount of metal contamination in the river is alarming and affecting the aquatic ecosystem of the river. Therefore further studies are needed on heavy metal speciation and their effects health on human and organisms via food chain.

Keywords: Awash River; Contamination, Heavy metal, Sediment and Index