Euphrates Turkey, in Syria and in Iraq. The same figures are given by Isaev and Mikhailova. The length of the Shatt al-Arab, which connects the Euphrates and the Tigris with the Persian Gulf, is given by various sources as . Both the Kara Su and the Murat Su rise northwest from Lake Van at elevations of and amsl, respectively. At the location of the Keban Dam, the two rivers, now combined into the Euphrates, have dropped to an elevation of amsl. From Keban to the Syrian–Turkish border, the river drops another over a distance of less than . Once the Euphrates
Tigris–Euphrates river system regime – drained to permit military access and greater political control of the native Marsh Arabs. Canals, dykes and dams were built routing the water of the Tigris and Euphrates Rivers around the marshes, instead of allowing water to move slowly through the marshland. After part of the Euphrates was dried up due to re-routing its water to the sea, a dam was built so water could not back up from the Tigris and sustain the former marshland. Some marshlands were burned and pipes buried underground helped to carry away water for quicker drying. The drying of the marshes led