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
Sawa Lake Sawa Lake Sawa Lake () is an Endorheic basin located in the Iraqi governorate of Muthanna near to the Euphrates River, some to the west of Al-Samawa city. This lake has no inlet or outlet, but it draws water from the Euphrates through a system of joint cracks and fissures which transport water to aquifers beneath it. The water's level fluctuates during dry and wet seasons but does not dry up because of the equilibrium state between water feed and evaporation. Lake Sawa is a unique body of water in Iraq since characterized by highest salinity value (up to 35