| Sedimentation in a dam reservoir is one of the important issues to overcome for utilizing the reservoir over a long term[1]. In addition, interrupting continuity of sediment transport by dams may cause downstream river flows to be sediment-starved (so-called hungry water), resulting in incision of river channels and/or coarsening of the bed materials[2]. In order to solve these situations, in Japan, sediment supply from reservoirs to their downstream rivers has been attempted using approaches such as sediment augmentation, sediment flushing and sediment bypass. However, there is limited knowledge on the impacts on the water quality just after the sediment supply operation despite the assumption that chemicals such as heavy metals are accumulated on the deposited sediment at the bottom of dam reservoirs.In this study, leaching tests of heavy metals from dam reservoir sediments were conducted to evaluate the occurrences of heavy metals in river water just after sediment supply. In addition, a short-term toxicity test was conducted to determine the toxicity of manganese (Mn) to Japanese medaka (Oryzias latipes). |
