Importance of Geohazard Studies in the Dam Design: Gotvand Dam ; A Geo-environmental Problem in SW Iran

The Gotvand-Olia Dam site is constructed on to implement the hydroelectric potentials of Catchment area of Karun River, in Khuzestan province, SW of Iran. It is first studied in 1960s. As it is reported by Iran Water and Power Resources Development Company (IWPRDC) in 2003, Mahab Qods Consulting Engineers were chosen as the project consultant for completing the studies of second phase and supervision of the operation. The Karun River originates from southern Zagros Mountains in Koohrang, Armand, Khorasan, Vang and Bazoft areas and after a distance of 80 kilometers along north-east to south-east, in Khorramshahr, joins Arvanrood and pours to the Persian Gulf. Considering the discharge, this river is the greatest river of Iran. Karun River’s average annual long-term discharge, in the area of dam construction is 453 m3/s and its annual discharge is more than 14 billion m3. The dam is designed to have a reservoir of 4.5 billion m3 capacity. The river was diverted by April 2003 and excavation began soon thereafter. After completion of the dam, impounding of its reservoir began on 30 July 2011. Phase 2 was estimated to be complete in 2015 and the dam was going to become one of Iran's largest power stations and is already its tallest earth-fill dam in Iran.Problem:Gotvand Dam is in operation since 2011 to supply the sugarcane plants in Khuzestan. The reservoir however is located in a region in folded Zagros belt and mountain foothills that lies on salt beds.1- There is a Salt-Gypsy mountain (Named "Anbar") 5km north of the dam site. There was constructed a cover on this Salty-Gypsy unit in order to avoid its dissolution during the operation of the Dam and when the reservoir covers this solvable unit.2- The salt concentration of the water is evidently increased in the Karun River after the operation of the Dam. The cover is damaged in 2013, and the Salty-Gypsy unit is solving gradually in the Karun River.3- The electro-conductivity (EC) of water is one indicator of its salinity, estimating the level of dissolved solids through the capacity of water to conduct electrical current. The EC level that sugarcane may with stand is 1.7 mS/cm (mili Siemens per centimeter) whereas the level is above 4 mS/cm in some areas around Shadegan and 17 near the water sources for the sugarcane plants.4- The environmental officials say in mid-2015 that the Gotvand dam contributed to the death of 400,000 palm trees in Arvandkenar region (downstream of Karun, 340km downstream of Gotvand Dam) in 2014, due to exponentially increasing the salinity of the Karoun River, which has made the already harsh environment unbearable for palm trees. The damage has severe implications on Iran’s agriculture and economy because 40% of Iran’s exported dates are produced in this southern province.

کلیدواژه ها:

Salt-Gypsy mountain ، electro-conductivity (EC) ،