THE TIGRIS AND EUPHRATES RIVER SYSTEM.

The Tigris and Euphrates, with their tributaries, form a major River System in Western Asia, the Westernmost subregion of Asia.
From sources in the Taurus Mountains of Eastern Turkey they flow by/through Syria through Irak into the Persian Gulf.
The Tigris is 1850 km long and 30 km in distance from the headwaters of the Euphrates. Then it flows for 400 km through Turkish territory before becoming the border between Syria and Turkey. This stretch of 44 km is the only part of the Tigris that is located in Syria. Bagdad, the capital of Iraq, stands on the banks of the Tigris. In ancient times, many of the great cities of Mesopotamia stood on or near the River, drawing water from it to irrigate the civilization of the Sumerians. Notable Tigris-side cities included Nineveh, Ctesiphon and Seleucia, while the city of Lagash was irrigated by the Tigris via a canal dug around 2400 BC.
The Euphrates is the longest River. It emerges from the confluence of the Kara Su River and the Murat Su River. Both rivers rise NorthWest from Lake Van, the largest saline Lake in Turkey, at elevations of 3290 m (10,790ft) and 3,520 m (11,550ft), respectively. The River receives most of its water in the form of rainfall and melting snow. In Syria, 3 Rivers add their water to the Euphrates. Once the Euphrates enters Iraq, there are no more natural tributaries to the river, although canals connecting the Euphrates Basin with the Tigris Basin exist. From the source of the Murat River to the confluence with the Tigris the length is 3000 km (1900mi), of which 1230 km (760mi) falls in Turkey, 710 km (440mi) in Syria and 1060 km (660mi) in Irak. During 3600-3100 BC, Southern Mesopotamia grew in numbers and size of settlements. Sumero-Akkadian sites like Sippar, Uruk, Adab and Kish, were organized in competing City-States. Many of these cities were along the canals of the Euphrates and Tigris. Large parts of the Euphrates were for the 1st time united under a single ruler in the Akkadian Empire (2335-2154BC) and Ur III Empires. Following their collapse, the Old Assyrian Empire (1975-1750BC). Then absorved by the newly emerged state of Babylonia under Hammurabi in the early to mid 18th century BC. In centuries to come, control of the wider Euphrates Basin shifted from the Neo-Assyrian Empire, which collapsed between 612 and 599 BC to the short lived Median Empire (612 -546BC) and equally brief Neo-Babylonian Empire(612-539BC) in the last years of the 7th centuryBC, and eventually to the Achaemenid Empire(539-333BC). They in turn were overrun by Alexander the Great, who defeated the last king Darius III and died in Babylon in 323 BC. Subsequent to this came the Seleucid Empire (312-150BC), Parthian Empire(150-226BC), and was fought over by the Roman Empire, its succeeding Byzantine Empire and the Sassanid Empire(226-638CE), until the Arab invasion of the mid 7th century CE.
The small tributaries feed into the System from shallow freshwater Lakes, Swamps, and Marshes, all surrounded by Desert. Historically the area is known as Mesopotamia.
The Tigris-Euphrates Basin is shared by Turkey, Syria, Iraq, Iran, and Kuwait. Many Tigris tributaries originate in Iran and a Tigris-Euphrates confluence forms part of the Kuwait-Iraq border.
The System is part of the PaleArctic (8th eco-zones constituting the Earth's surface, and the largest (Europe, Asia North of the Himalaya foothills, Northern Africa, and the Northern and Central parts of the Arabian Peninsula) 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 through the Central Plain and the Rivers join in a small Town (Al-Qurnah) in Southern Irak to form the Shatt al-Arab and discharge into the Persian Gulf.
The marshlands were an extensive natural wetlands ecosystem which developed over Thousands of years in the Basin and once covered 15-20,000 square kms. Irak suffers now from desertification and soil salination due in large part to thousands of years of agricultural activity. Water and plant life now are sparse. Government Water-Control Projects drained the inhabited marsh areas by drying up or diverting streams and rivers. The destruction of the natural habitat poses serious threats to the area's wildlife populations. There are also inadequate supplies of potable water.
Local folklore holds Qurna to have been the site of the Garden of Eden. An ancient Jujube Tree (recently dead) is locally celebrated as the actual Tree of Knowledge of the Bible. The Jujuba is a small deciduous tree reaching a hight of 5-12 m (16-39ft), usually with thorny branches.
The concept Western Asia is in limited use, as it significantly overlaps with the Middle East (Near East), the main difference being the exclusion of Egypt (counted as part of North Africa). The total population of Western Asia is estimated at about 300 millions as of 2015.
In ancient history and archaeology the term is used to divide the Fertile Crescent into the Western Asia Cultures as opposed to Ancient Egypt.