Author(s): Sebastian Guillen Ludena; Jorge A. Toapaxi; Luis G. Castillo

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Keywords: Reservoir sedimentation; Flushing; Efficiency; Sediment dynamics

Abstract: Reservoir sedimentation is nowadays a major concern in the operational management of dams. The increasing volume of sediments deposited in reservoirs reduce their storage capacity and negatively affects their sustainability. In this context, sediment flushing has been reported as one of the most efficient techniques to mitigate the negative effects related to reservoir sedimentation. The efficiency of this technique is defined herein as the ratio of the volume of sediment evacuated with respect to the volume of water released (Vs / Vw). This efficiency depends on factors such as the planform geometry of the reservoir, the discharge capacity of the bottom outlets, the initial water head (hw), the volume of water initially stored, the thickness of the sediment bottom layer (hs), and the sediment characteristics. This study aims to assess the efficacy of flushing operations for different initial water heads (hw) and stored volumes (Vw), different bed slopes (S0), and different grain sizes of sediments (D*). To this end, 90 laboratory experiments have been conducted, in which ten pairs of values hw – hs have been tested for three reservoir lengths, three initial bed slopes and three sediment sizes. The results show that the volume of sediment evacuated (Vs) increases as Vw, S0, and hs increase. In turn, the flushing efficacy increases as S0 increases, and it decreases as Vw / hs3 increases. In this study, the effect of the sediment size both on Vs and on Vs / Vw was reduced, because the critical boundary shear was similar for the three tested sediment mixtures.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221462

Year: 2022