Fine sediment routing in a cascade of alpine reservoirs: Influence of the inlet angle on settling of fine sediments

Reservoir sedimentation is, at present, one of the main concerns in the operational management of dams. The resulting reduction of storage capacity has negative impacts on the hydropower production, flood protection, and availability of water for irrigation and human consumption. Previous studies suggest that the most efficient and sustainable measures to cope with sediment settling consist in providing continuity to the sediment flux from the tail to downstream of the reservoir, avoiding sedimentation. In pumped-storage hydropower schemes, the cyclic flow exchange between two reservoirs can contribute significantly to inhibit sediment settling, by maintaining or increasing the turbulence levels in the vicinity of the water inlets/outlets. This study aims firstly at exploring the interaction between hydrodynamics and sedimentation processes in a reservoir with a given initial concentration. Secondly, this study aims at analyzing the evolution of an initial sediment concentration in a reservoir, under the influence of a horizontal jet-like inflow for different angles of incidence and discharges. For those purposes, numerical simulations were conducted for an alpine reservoir (Räterichsboden) by means of Ansys CFX. The results will allow characterizing the interaction between the jet-like inflow and the sedimentation processes.