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
Euphrates enters the Upper Mesopotamian plains, its grade drops significantly; within Syria the river falls while over the last stretch between Hīt and the Shatt al-Arab the river drops only . The Euphrates receives most of its water in the form of rainfall and melting snow, resulting in peak volumes during the months April through May. Discharge in these two months accounts for 36 percent of the total annual discharge of the Euphrates, or even 60–70 percent according to one source, while low runoff occurs in summer and autumn. The average natural annual flow of the Euphrates has been determined from