Page - 538 - in Book of Full Papers - Symposium Hydro Engineering

Different scenarios were considered for the estimation of annual amount of deposition simulated with the 1D model RESSASS. The results show that the reservoir is likely to be filled in about five years. The average annual amount of sediment deposits is around 2 MT(annual sediment inflow is about 4.2MT) per year. Several scenarios were considered for the distribution of the sediments near the weir with a 2D modelling system TELEMAC-SYSIPHE-HR. The results show that in front of the intake, deposition occurs in all cases up to the elevation of about 760m asl. The invert of the intakes is at 750m asl. During high flows, the model results show a sand bar forming between the intakes and the weir gates, reaching almost the water level surface. These problems led to the consideration of new sediment management methods. Fig 4. Bed Evolution During Deposition(left) and Deposition after 48days(Q=153m3/s)(right) 3.2. OHDS TECHNIQUE Generally, management activities to address reservoir sedimentation may be classified into four broad categories (Morris, 2015). Among them, the Patrind Hydropower Project adopted “Route Sediments” and “Remove and Redistribute Sediment Deposits” to handle inflow sediments. We called adopted method “OHDS technique”. This technique was developed by Alam(2014) considering that the flows exceeding the capacity of the intake(153m3/s) would be diverted through a by-pass tunnel. The area of the reservoir and modified pool(hereafter called MP), between the cofferdam and the weir was conceived as acting as a natural sand trap. As this area has a larger volume that the designed sand traps and considering low velocities than in the sand traps, its efficiency should be higher than that of the artificial sand traps. 538