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 Euphrates is connected with the Tigris. The largest canal in this network is the Main Outfall Drain or so-called "Third River;" constructed between 1953 and 1992. This canal is intended to drain the area between the Euphrates and the Tigris south of Baghdad to prevent soil salinization from irrigation. It also allows large freight barges to navigate up to Baghdad. The construction of the dams and irrigation schemes on the Euphrates has had a significant impact on the environment and society of each riparian country. The dams constructed as part of GAP – in both the Euphrates and the Tigris