Evaluation of different strategies for management of reservoir sedimentation in semi-arid regions: a case study (Dez Reservoir)

Emamgholizadeh S, Bateni SM, Nielson JR. 2018. Evaluation of different strategies for management of reservoir sedimentation in semi-arid regions: a case study (Dez Reservoir). Lake Reserv Manage. 00:00-00.Reservoir sedimentation is a major concern, especially in arid and semi-arid areas, such as Iran. Dez Reservoir, with a primary storage capacity of 3315 x 10(6) m(3), located on the Dez River, is an important dam in Iran that suffers from sedimentation problems. Large volumes of sediments are impounded every year in this reservoir, particularly during hyper-concentrated floods. The accumulation of sediments in the Dez Reservoir has negatively impacted its utilities, such as power generation, flood control, and water supply. In this study, several different strategies of sedimentation management were assessed, including watershed management, sluicing, flushing, density current venting, and bypass. The results show that sedimentation in the Dez Reservoir can be reduced by 11-15% by venting density currents, which entails discharging incoming density currents through irrigation gates before they get impounded in the reservoir. Sedimentation can be reduced by approximately 2% by pressure flushing, which would decrease sediment depositions near the power plant intake. By construction of a submerged dam 9km upstream of Dez Dam Reservoir, the bypass technique can be used to release 10.8 x 10(6) m(3) of sediments per year and discharge turbid flow during the flood season. Finally, implementing watershed management strategies in the Sezar catchment could reduce the inflowing sediment to Dez Reservoir by 15%. Dez Reservoir does not have sluice gates and, therefore, the free flushing and sluicing methods cannot be used as mitigation strategies.