The assessment of a river water’ quality is an essential procedure of monitor programs and isused to collect basic environmental data. The management of integrated water resources in asustainable method is also necessary to allow future generations to meet their water needs. Themain objective of this research is to assess the effect of the Diyala River on Tigris River waterquality using Geographic Information System (GIS) technique. Water samples have beencollected monthly from November 2017 to April 2018 from four selected locations in Tigris andDiyala Rivers using the grab sampling method. Fourteen parameters were studied which areTurbidity, pH, Dissolved Oxygen, Biological Oxygen Demand, Electrical Conductivity, TotalDissolved 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 Rivernearly affected by the water quality of the Diyala River within the locations selected. The mapsalso reveal that in March and April 2018 the quality of surface water got a sudden peakcompared with the other months. This is due to the increase in both the parameter of Turbidityand Total Dissolved Solids. (PDF) The Effect of Diyala River Water Quality on the Quality of Tigris River Water using GIS Mapping. Available from: https://www.researchgate.net/publication/336272200_The_Effect_of_Diyala_River_Water_Quality_on_the_Quality_of_Tigris_River_Water_using_GIS_Mapping [accessed Apr 07 2023].