Tigris–Euphrates river system through the central plain and combine at Al-Qurnah to form the Shatt al-Arab and discharge into the Persian Gulf. The region has historical importance as part of the Fertile Crescent region, in which civilization is believed to have first emerged. The ecoregion is characterized by two large rivers, the Tigris and Euphrates. The rivers have several small tributaries which feed into the system from shallow freshwater lakes, swamps, and marshes, all surrounded by desert. The hydrology of these vast marshes is extremely important to the ecology of the entire upper Persian Gulf. Historically, the area is known as Mesopotamia. As
Euphrates that the river was a divinity. In Sumerian, the name of the city of Sippar in modern-day Iraq was also written UD.KIB.NUN, indicating a historically strong relationship between the city and the river. The Euphrates is the longest river of Western Asia. It emerges from the confluence of the Kara Su or Western Euphrates () and the Murat Su or Eastern Euphrates () upstream from the town of Keban in southeastern Turkey. Daoudy and Frenken put the length of the Euphrates from the source of the Murat River to the confluence with the Tigris at , of which is in