evidence: The Shatt al-Arab, known in Iran as the Arvand Rud, is a river in Southwest Asia stretching more than 200 kilometers (124 mi) in length. It is formed by the confluence of the Euphrates and the Tigris in the town of al-Qurnah in southern Iraq. The southern end of the river constitutes the border between Iraq and Iran to the mouth of the river where it discharges into the Persian Gulf. The river varies in width from about 232 meters (760 ft) at Basra to 800 meters (2,600 ft) at its mouth. It is thought that the waterway formed relatively recently in geologic time, with the Tigris River and Euphrates River originally emptying into the Persian Gulf via a channel farther to the west. [...] The Shatt al-Arab suffers from the religion and politics of the neighboring nations, Iran and Iraq, whose border falls in the river at its southern end. But control of the waterway and its use as a border have been a source of contention between the predecessors of the Iranian and Iraqi states since a peace treaty was signed in 1639 between the Persian and the Ottoman Empires. UnderSaddam Hussein, Iraq claimed the entire waterway up to the Iranian shore as its territory and invaded Iran in 1980 to back this up. [...] Notes - ↑ United Nations Environment Programme, Shatt al-Arab Retrieved September 12, 2015.