Tigris–Euphrates river system through the central plain and combine at Al-Qurnah to form the Shatt al-Arab and discharge into the Persian Gulf. The region has historical importance as part of the Fertile Crescent region, in which civilization is believed to have first emerged. The ecoregion is characterized by two large rivers, the Tigris and Euphrates. The rivers have several small tributaries which feed into the system from shallow freshwater lakes, swamps, and marshes, all surrounded by desert. The hydrology of these vast marshes is extremely important to the ecology of the entire upper Persian Gulf. Historically, the area is known as Mesopotamia. As
Water politics in the Jordan River basin the salinity of the tributary Yarmouk River is also satisfactory, at 100 ppm, but the lower Jordan river becomes progressively more saline as it flows south. It reaches twenty-five percent salinity (250,000 ppm) where it flows in the Dead Sea, which is about seven times saltier than the ocean. As a resource for freshwater the Jordan River drainage system is vital for most of the population of Palestine, Israel and Jordan, and to a lesser extent in Lebanon and Syria who are able to use water from other national sources. (Although Syrian riparian rights to the Euphrates has been severely