The assessment of a river water’ quality is an essential procedure of monitor programs and is used to collect basic environmental data. The management of integrated water resources in a sustainable method is also necessary to allow future generations to meet their water needs. The main objective of this research is to assess the effect of the Diyala River on Tigris River water quality using Geographic Information System (GIS) technique. Water samples have been collected monthly from November 2017 to April 2018 from four selected locations in Tigris and Diyala Rivers using the grab sampling method. Fourteen parameters were studied which are Turbidity, pH, Dissolved Oxygen, Biological Oxygen Demand, Electrical Conductivity, Total Dissolved Solids, Total Hardness, Calcium, Magnesium, Chloride, Sulphate, Phosphate, Sodium, and Total Alkalinity. The results of GIS maps showed that the water quality of the Tigris River nearly affected by the water quality of the Diyala River within the locations selected. The maps also reveal that in March and April 2018 the quality of surface water got a sudden peak compared with the other months. This is due to the increase in both the parameter of Turbidity and Total Dissolved Solids.
