Sediment management at run-of-river reservoirs using numerical modelling

The worldwide storage volume of reservoirs is estimated to decrease by 0.5-1% per year due to sedimentation, which is higher than the gain in volume by newly built dams. For water supply or flood protection, the preservation of the storage volume is crucial. Operators and authorities, therefore, need sediment management concepts to ensure that the storage volume is sufficient. In this study, we developed a sediment-flushing concept using 2D numerical modelling for a run-of-river hydropower plant located in the Saalach River in southeastern Germany. The calibrated bed elevation was used as the initial bed for a number of simulations with different discharge regimes under varying operational schemes. By comparing the simulated results, we propose an appropriate flushing scheme in terms of intensity and duration to obtain a balance of sediment regime in the river. Furthermore, we demonstrate that such an optimised sediment management can generate synergies for improving measures of flood protection.