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
Geography of Syria and most important river is the Euphrates, which represents more than 80 percent of Syria's water resources. Its main left-bank tributaries, the Balikh and the Khabur, are small perennial rivers that both rise in the Syro-Turkish border region. The right-bank tributaries of the Euphrates are mostly small seasonal streams called wadis. In 1973, Syria completed construction of the Tabqa Dam on the Euphrates River upstream from the town of Raqqa. The dam created a reservoir named Lake Assad (Buhayrat al Assad), a body of water about 80 kilometers long and averaging eight kilometers in width. Throughout the arid plateau region