Author(s): Mehrdad Sepehri; Mahdi Soudkhah; Ali Paknejad
Keywords: Sediment; Dredger; Dez Dam; Hydropower Intake; Operating management
Abstract: Construction of Dez Dam and its hydropower plant on the north of Dezful in Khuzestan was completed in 1962 and reservoir impoundment commenced in December 1962. At present, this hydropower plant is one of the most important in Iran as it also regulates the frequency of the electrical grid. Unfortunately sedimentation especially near the Dam with a deposit thickness of 90 m has created many difficulties for dam operation. First of all the irrigation gates of the Dam, which are presently 35m under sediment deposit are out of use. This has resulted in diverting the hydropower outflow for irrigation. Now the hydropower intake is only 12m above deposits and if dredging is delayed, hydropower generation/operation will be difficult. High volume of input sediments and high percentage of density current indicates that in order to increase the life of dam, a big part of density current should be vented through irrigation gates. In this paper predicted volume of input sediments and actual measured deposited sediments and density currents are studied. Then, the encountered problems related to dredging of sediments for creation of a basin besides irrigation gates will be stated. Finally, the method for dredging around the irrigation gates, power station intakes, and the characteristics of appropriate dredger, which is unique case in the world, will be discussed. Operating management will be considered as a major issue in appropriate dumping the sediments in the river downstream of the dam with the aim of environmental observations.