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
Karasu (Euphrates) pitch by locals. Karasu (Euphrates) The Karasu (Turkish for 'black water') or Western Euphrates is a long river in eastern Turkey, one of the two sources of the Euphrates. It has a length of about 450 km. To the ancient Greeks the river was known as the ("Telebóas"). The river rises on the Dumlu Dağ in Erzurum Province, and drains the plains around the city of Erzurum. It is joined by the Serçeme River, then flows west through Erzincan Province, turning south, then west and receiving the tributary Tuzla Su. Between Erzincan and Kemah it is joined by the Gönye