Tigris–Euphrates river system Tigris–Euphrates river system The Tigris and Euphrates, with their tributaries, form a major river system in Western Asia. From sources originating in eastern Turkey, they flow by/through Syria through Iraq into the Persian Gulf. The system is part of the Palearctic Tigris–Euphrates ecoregion, which includes Iraq and parts of Turkey, Syria, Iran, Saudi Arabia, Kuwait, and Jordan. From their sources and upper courses in the mountains of eastern Anatolia, the rivers descend through valleys and gorges to the uplands of Syria and northern Iraq and then to the alluvial plain of central Iraq. The rivers flow in a south-easterly direction
Euphrates and Iraq. Apart from the changes in the discharge regime of the river, the numerous dams and irrigation projects have also had other effects on the environment. The creation of reservoirs with large surfaces in countries with high average temperatures has led to increased evaporation; thereby reducing the total amount of water that is available for human use. Annual evaporation from reservoirs has been estimated at in Turkey, in Syria and in Iraq. Water quality in the Iraqi Euphrates is low because irrigation water tapped in Turkey and Syria flows back into the river, together with dissolved fertilizer chemicals used