SHATT-AL-ARAB, a river in Mesopotamia formed by the junction of the Tigris and the Euphrates (qq.v.). There is reason to believe that the stream is not of great antiquity. (See MESO POTAMIA : Ancient Geography.) The Shatt-al-Arab may be said to extend from Qurna to the bar at Fao, and the effect of the tide reaches up to the former point, where formerly the Euphrates discharged. It is 123 miles long. The importance of the Shatt al-Arab is restricted to its lower reach from Basra to Fao, the railway from Baghdad having its terminus at Basra. Between Basra and Mohammera, the Persian port at the junction of the Karun with the Shatt-al-Arab, the river has an average breadth of 600 yards. At the actual point of junction the river widens out to half a mile and at Fao, 49 m. down stream, it is a mile broad. Below Fao the river rapidly widens and flows through in terminable sandbanks and mudflats to the Persian Gulf.
The utility of the river for navigation is restricted by the bar at Fao, which allows only vessels of under I I ft. draught to pass at low water. Sir Arnold Wilson has computed that the silt coming down the river annually is about half a million tons; the amount deposited in the main channel would be insignificant if, after dredging, a channel of 24 ft. at low water were maintained.
Beyond the bar there is a depth of 3o-4o ft. except in two places, the bar at Mohammera at the confluence of the Karun being the only other serious restriction to navigation.
Rawlinson suggests that there are three main facts to be con sidered in the history of the Shatt-al-Arab. First the coast line at the mouth of the Shatt-al-Arab advanced very slowly until, at the end of the 18th century, the Karun forced its way into the Shatt al-Arab. When this happened the Shatt-al-Arab began to enlarge its bed and began to cut the great bend between Mohammera and Abadan. After this islands began to form at the mouth of the Shatt-al-Arab. (See also MESOPOTAMIA, and BASRA.) BIBLIOGRAPHY.-Sir W. Willcocks, The Irrigation of Mesopotamia (191I) ; Memorandum respecting the Navigation of the Tigris and the Euphrates (1913) ; Sir A. Wilson, "The Delta of the Shat-al-Arab and Proposals for Dredging the Bar," Geographical Journal, lxv., p. 225 (1925) ; Colonial Office annual Reports.