Tigris-Euphrates river system, great river system of Southwest Asia, comprising the Tigris and Euphrates rivers, which have their sources within 50 miles (80 km) of each other in eastern Turkey and travel southeast through northern Syria and Iraq to the head of the Persian Gulf. The lower portion of the region that they define, known as Mesopotamia (Greek: “Land Between the Rivers”), was one of the cradles of civilization. The total length of the Euphrates(Sumerian: Buranun; Akkadian: Purattu; biblical: Perath; Arabic: Al-Furāt; Turkish: Fırat) is about 1,740 miles (2,800 km). The Tigris (Sumerian: Idigna; Akkadian: Idiklat; biblical: Hiddekel; Arabic: Dijlah; Turkish: Dicle) is about 1,180 miles (1,900 km) in length.The rivers usually are discussed in three parts: their upper courses, restricted to the valleys and gorges of eastern Anatolia, through which the rivers descend from their sources, lying 6,000 to 10,000 feet (1,800 to 3,000 metres) above sea level; their middle courses, in the uplands of northern Syria and Iraq, at elevations varying from 1,200 feet (370 metres) at the foot of the so-called Kurdish Escarpment to 170 feet (50 metres) where the rivers empty onto the plain of central Iraq; and their lower courses across this alluvial plain, which both rivers have created jointly. At Al-Qurnah the rivers join to form the Shatt al-Arab.