Asymmetic sediment flux due to tidal power generation in the lake sihwa

The hydrodynamics associated with the power generation in the tidal power plant is an important factor in transporting and eroding the bed sediment in the Lake Sihwa, South Korea. In the power generation phases, the tidal current flows from the sea into the enclosed basin, whereas in the discharge phases, the outgoing water passes through the sluice gate. During these two phases, there is a difference of sediment transport due to asymmetric hydrodynamics. To investigate the effect of power generation on the sediment dynamics, a mooring was conducted during 20 days near the Lake Sihwa. During the power generation phases, the mean current speed and suspended sediment concentration (SSC) were respectively about 0.61 m s-1 and 71.72 mg l-1, whereas they were about 0.14 m s-1 and 33.85 mg l-1 during the discharge phases. There were double peaks in SSC during power generation (Fig. 1). The first peaks (91.57 and 65.12 mg l-1) in SSC were related to deaccelerating phases in current, whereas second peaks (90.12 and 75.17 mg l-1) were related to second accelerating phases in current. During the discharge phases, there were a peak in SSC associated with artificial discharge through sluice gates. In these periods, the SSC increased up to 51.36 and 53.11 mg l-1. The results exhibited the significant difference of sediment suspension between power generation and discharge phases. The SSC during the discharge to sea was approximately 45% of that during the power generation. The asymmetric sediment suspension between power generation and discharge may drive the suspended sediment into the basin, which may cause the acceleration of sedimentation inside Lake Sihwa.