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
Cordes (river) Cordes (river) Cordes () was a small stream of Mesopotamia which rose in the Mons Masius, and was a tributary of the Chaboras, itself a tributary of the Euphrates. The town of Dara was situated upon its banks. Justinian's engineers diverted the river towards the city by digging a canal. The river now flowed through the city, ensuring ample water supply. At the same time, by means of diverting its flow to an underground channel which exited to the north, Dara's garrison was able to deny water to a besieging enemy, a fact which saved the city on several occasions.