International Journal of Aquatic Science ISSN: 2008-8019 Vol 12, Issue 02, 2021 3814 Cluster analysis for classification water quality of Shatt Al-Arab river Mujtaba, A. T. Ankush 1 , Ghassan A. Al-Nagar 2 , Faris J. M. Al-Imarah 3 1 Department of Fisheries and Marine Recourses, College of Agriculture, Basrah Univesity, Basrah, Iraq 2 Department of marine invertebrate, Marine Science Center, Basrah University, Basrah, Iraq 3 Department of Chemistry and Marine Environmental Pollution, Marine Science Center, Basrah University, Basrah, Iraq E-mail: jumuajd@yahoo.com 1 Abstract: Cluster analyses technique has been used to assess for the classification of water quality of Shatt Al-Arab river for drinking purposes. Three stations ahead of water treatment plants have been chosen, St.1, upper stram of Shatt Al-Arab River close to the main water treatment plant and it is effected by discharging of untreated waste from little small scale industries. St.2, Salhia which is about 4 km downstream st.1 close to Al- Bradhiah water treatment plant and it is effected heavily by cattle bathing and discharge of laundering cloths. St.3, Abu Al-Khaseeb about 7 km downstream st.1, close to Mhellah water treatment plant. All stations are effected heavily by waste water from Basrah City. Cluster analysis grouped the 11th physico-chemical parameters of the three selected sampling stations within Shatt Al-Arab river and during the period of study into three clusters at (Dlink/Dmax) x 100 < 80 :1st DO and Trans. , 2nd pH, and 3rd all the rest of the studied water parameters. And Results suggested three sources of water quality which cause an overall water quality of Shatt Al-Arab River. KeyWards: Shatt Al-Arab river, water quality, cluster analysis, physico-chemical parameters, multivariate. 1. INTRODUCTION Anthropogenic activities as well as natural processes and climatic changes are main factors for rapid change in the quality of surface water (Akbar et al., 2013). Water quality of Shatt Al-Arab river is effected by waste water discharge from Basrah city represented by certain vital pollutants, and climatic factors represented by dust fall which carries heavy metals, salts, and petroleum hydrocarbons (CCME, 2001). Water quality classifications facing a certain problems in which cluster analysis is the data analysis tool to solve such problems as well as determination of pollution sources ( Ozbay et al., 2009), or even effected by pollutants transport through upstream rivers, Tigris, Euphrates as well as tributaries of Shatt Al-Arab river itself from landfills and marshlands ( Al-Imarah et al., 2017). Water quality is the main concern if the major interest is for drinking purposes ( Higler, 1988). A multivariate statistical techniques s (uch as cluster analysis was used to assess the