Answer:
The Euphrates river
Explanation:
Along with the Tigris, the Euphrates river helped form the Fertile Crescent and the Sumerian civilization.
It starts where the Karasu and Murat rivers merge in eastern Turkey and continues southeasterly for 2800 km (1740 mi) through Syria and Iraq until it merges with the Tigris river at Al-Qurnah. There, it becomes the Shatt al-Arab waterway and empties into the Persian Gulf.
