WIT Press

The Flushing Of The Sediments Near The Power Intakes In The Dez Reservoir


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WIT Press


S. Emamgholizadeh, H. Samaadi Borojeni & M. Bina


The Dez Dam was constructed in 1963 on the Dez River with the purpose of power generation, irrigation, water supply and flood control. It is a double curvature concrete arch dam with a height of 203 meters and initial storage capacity of 3315MCM. In this operational period, a sedimentation rate of 15 to 20 MCM/year had caused the sediment level behind the dam to raise up to 12 m below the power intakes (with a rate of 2 m/year) and the delta front has progressed 0.5 to 1 km/year towards the dam. Currently, the major issue which threatens the Dez Dam is the continual accumulation of silt in the reservoir near the dam. This situation has potential impact on the physical operations at the dam, including power generation and reservoir operation in general. Thus it is vital that the sediment level near the power intakes be decreased. Current research has shown that by using cone flushing via three outlets which are located at el. 222.7 m within the central blocks of the dam body (129 m below the full supply level of the reservoir), we can remove nearly 0.3 MCM and draw down the height of the sediments near the power intake about 13 to 15 m. In addition a bathymetry of the scour cone after a complete pressure flushing shows that the submerged slope of the reposed sediments is variable from 45% to 6%. Keywords: reservoir, sedimentation, flushing, Dez Dam. 1 Introduction During the past few decades dams and reservoirs have been built with increased frequency, and even more are under considering or construction. Without dams, the eroded soil is transported by river flows to the sea. However, when dams are


reservoir, sedimentation, flushing, Dez Dam.