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Environmental and social effects

The construction of the dams and irrigation schemes on the Euphrates has had a significant impact on the environment and society of each riparian country. The dams constructed as part of GAP – in both the Euphrates and the Tigris basins – have affected 382 villages and almost 200,000 people have been resettled elsewhere. The largest number of people was displaced by the building of the Atatürk Dam, which alone affected 55,300 people. A survey among those who were displaced showed that the majority were unhappy with their new situation and that the compensation they had received was considered insufficient. The flooding of Lake Assad led to the forced displacement of c. 4,000 families, who were resettled in other parts of northern Syria as part of a now abandoned plan to create an " Arab belt " along the borders with Turkey 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 2 cubic kilometres (0.48 cu mi) in Turkey, 1 cubic kilometre (0.24 cu mi) in Syria and 5 cubic kilometres (1.2 cu mi) 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 on the fields. The salinity of Euphrates water in Iraq has increased as a result of upstream dam construction, leading to lower suitability as drinking water. The many dams and irrigation schemes, and the associated large-scale water abstraction, have also had a detrimental effect on the ecologically already fragile Mesopotamian Marshes and on freshwater fish habitats in Iraq.

The inundation of large parts of the Euphrates valley, especially in Turkey and Syria, has led to the flooding of many archaeological sites and other places of cultural significance. Although concerted efforts have been made to record or save as much of the endangered cultural heritage as possible, many sites are probably lost forever. The combined GAP projects on the Turkish Euphrates have led to major international efforts to document the archaeological and cultural heritage of the endangered parts of the valley. Especially the flooding of Zeugma with its unique Roman mosaics by the reservoir of the Birecik Dam has generated much controversy in both the Turkish and international press. The construction of the Tabqa Dam in Syria led to a large international campaign coordinated by UNESCO to document the heritage that would disappear under the waters of Lake Assad. Archaeologists from numerous countries excavated sites ranging in date from the Natufian to the Abbasid period, and two minarets were dismantled and rebuilt outside the flood zone. Important sites that have been flooded or affected by the rising waters of Lake Assad include Mureybet, Emar and Abu Hureyra. A similar international effort was made when the Tishrin Dam was constructed, which led, among others, to the flooding of the important Pre-Pottery Neolithic B site of Jerf el Ahmar. An archaeological survey and rescue excavations were also carried out in the area flooded by Lake Qadisiya in Iraq. Parts of the flooded area have recently become accessible again due to the drying up of the lake, resulting not only in new possibilities for archaeologists to do more research, but also providing opportunities for looting, which has been rampant elsewhere in Iraq in the wake of the 2003 invasion.