Effect of Upper Zab River Confluence Point on The Quality Characteristics of Tigris River Water

Many sources play a significant role in changing the Tigris river water quality within Iraqi territory, such as the river's tributaries receiving points, impounding like Mosul dam, the residential settlements as Mosul city, and the untreated discharge of agricultural activities.The First river tributary is Khabbor which confluences the Tigris River at Feshkhaboor village, near the Iraqi-Turkish borders. The second one is Upper Zab which meeting the river at Mishraq, 45 Km south of Mosul. Upper Zab Tributary is characterized by high discharges rates, and high pollution content. The study aim to evaluate its effect on the Tigris river water quality.The Study revealed that the Upper Zab river has buffering capacity that polishes or enhances the Tigris river water characteristics, with an adverse effect for the others. For example, the values increased by 6% for pH, 56% for Dissolved oxygen, and 134.5% for alkalinity, Whereas the other characteristics decreased by 27.7% for electrical conductivity, 23.6% for total solids, 40% for suspended solids,16.5% for calcium ion, 20% for chloride, 33% for sulfate, 50% for chemical oxygen demand, and 6% for biological oxygen demand.