天竜川の砂州における湧水流路の形成過程と生息場機能

Abstract

Prolonged turbidity derived from dam sedimentation upper stream has been one of the worst environmental problems in the Tenryu River, reducing algal production and quality of spawning redds for Ayu-fish. In this study, we assumed that the harmful effects of turbidity would be compensated by the spring flows in the sandy bar structure created during previous floods. In order to certify the hypothesis we made a series of fieldworks at seven sites in spring flow channels newly created in 2018 and we found spawning redds of Ayu-fish at three sites in the channels. The results indicate that the wild population of Ayu-fish in Tenryu River is owing to the newly created spring flow channels for their reproduction.