The Euphrates River originates in Turkey; it flows southwesterly across west-central Turkey, then southeast through Syria and Iraq, ending in the waters of the Arabian Gulf. It joins with the Tigris in southern Iraq, and from there continues south to Shatt al Arab. Overall it is 2,780km (1,730miles) in length, and is the longest river in the Middle East. 40% of it is in Turkey, 25% in Syria and 35% in Iraq. In ancient times the cities of Sippar, Uruk, Ur, and Babylon flourished on the banks of the lower Euphrates. Major cities today include Raqqa and Deir al Zor in Syria and Karbala and Najaf in Iraq.

The upper Euphrates flows rapidly through deep canyons and narrow gorges in Anatolia. In 1990, Turkey built the Atatürk Dam, one of 22 dams planned on the Euphrates that will provide plenty of water for irrigation upstream; at the same time this huge diversion of water in Turkey has negative implications for Syria and Iraq which rely on the river. The reservoir behind the dam requires occasional one-month interruptions in the flow of the river for refilling.

The waters of the middle Euphrates are used to irrigate the plains of Syria, an arid country which depends on the Euphrates for over half its water needs. In 1973 al Thawra Dam was completed in northern Syria. The dam is 70m (230 ft m) high, and creates the 640 sq km Assad Reservoir which provides electrical power. In eastern Syria the Euphrates is joined by the Khabur and Balikh Rivers.

As it flows along the eastern edge of the Syrian Desert and into Iraq, the river loses speed, and Iraq receives a river with high salt content resulting from the upstream activities. In northern Iraq the river is studded with islands, some with remains of old castles. Agriculture in Iraq, as in Syria, depends on the supply of water from the river system. Irregularities in flow make Iraqi agriculture vulnerable to drought. A dam at Haditha in west central Iraq was completed in 1986 to provide a water reserve for the country.

Before merging with the Tigris at Basra, the Euphrates divides into many channels, forming the Iraqi ahwar marshlands.

The Euphrates can be navigated only with shallow-draft boats.

Reference: The Columbia Encyclopedia, Sixth Edition.