The Great Zab or Upper Zab ( (al-Zāb al-Kabīr), or , , (zāba ʻalya)) is an approximately long river flowing through Turkey and Iraq. It rises in Turkey near Lake Van and joins the Tigris in Iraq south of Mosul. The drainage basin of the Great Zab covers approximately , and during its course, the rivers collects the water from many tributaries. The river and its tributaries are primarily fed by rainfall and snowmelt – as a result of which discharge fluctuates highly throughout the year. At least six dams have been planned on the Great Zab and its tributaries, but construction of only one, the Bekhme Dam, has commenced but was halted after the Gulf War. The Zagros Mountains have been occupied since at least the Lower Palaeolithic, and Neanderthal occupation of the Great Zab basin has been testified at the archaeological site of Shanidar Cave. Historical records for the region are available from the end of the third millennium BCE onward. In the Neo-Assyrian period, the Great Zab provided water for irrigation for the lands around the capital city of Nimrud. The Battle of the Zab – which ended the Umayyad Caliphate – took place near a tributary of the Great Zab, and the valleys of the river provided shelter for refugees from the Mongol conquest of Iraq. During the 19th and 20th centuries, the Great Zab basin saw frequent uprisings of local Kurdish tribes striving for autonomy. Course The Great Zab rises in Turkey in the mountainous region east of Lake Van at an elevation of approximately amsl and joins the Tigris on its left bank in Iraq. In Turkey, the Great Zab traverses the provinces of Van and Hakkâri, whereas in Iraq it flows through Duhok Governorate and Erbil Governorate, both part of the Kurdistan Region. Together with the Tigris, the Great Zab forms the boundary between Erbil Governorate and Ninawa Governorate. In its upper reaches, the Great Zab flows through steep, rocky gorges. The stretch between Amadiya and the Bekhme Gorge, where the Bekhme Dam remains unfinished, has been called the Sapna valley and will have a large portion of it inundated with water if the project is completed. Numerous mountain streams and wadis join the Great Zab on its right and left banks. The Great Zab receives most of its waters from the left-bank tributaries; the Rubar-i-Shin, Rukuchuk, Rubar-i-Ruwandiz, Rubat Mawaran and Bastura Chai.