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
Sajur River join the Euphrates on Syrian soil – the other two being the Balikh and the Khabur. The Sājūr is also the only river in Syria that enters the Euphrates on its right bank; both the Balikh and the Khabur flow into the Euphrates on the left bank. The Sājūr drains a total area of . The Syrian part of the Sājūr basin – the Manbij Plain – has been particularly well-studied. This area is bounded on the north by the Syro–Turkish border and extends as far south as Manbij. To the west, the Manbij Plain is bordered by basalt outcrops;