Establishment of the comprehensive river environment conservation system in collaboration with river stakeholders on the Tenryu River

The sedimentation, turbid water and water quality are typical environmental issues for dams and reservoirs which have impact on the reservoir and downstream of dams. These impacts are influenced from the upstream of a dam, and influence to the downstream. Therefore, a more integrated environmental management approach and consideration have been required for the whole river system. The Tenryu River in Japan flows through the erodible area near the Median Tectonic Line on Honshu, the main island of Japan, and continuously carries a lot of sediment during floods. The “Tenryu River Natural Resources Rebirth Promotion Committee” was established in 2012. The purpose of the committee is to restore fish resources and improve the river environment. The feature of the liaison committee is that it is composed of the Tenryu River fisheries association, academic experts, and dam owner and exchanges knowledge and technology information in spite of each interest. The current activities are related to the theme of “attached algae/environmental DNA survey”, “turbid water measures in reservoir/spawning bed construction technique at downstream,” and “information dissemination”. In this paper, the activities of the comprehensive reservoir and river environment conservation system in collaboration with river stakeholders are introduced and described, including future prospects