Author(s): Makoto Umeda, Bunyu Kobori

Linked Author(s): Makoto Umeda

Keywords: Reservoir; Stratified flow; Velocity distribution;

Abstract: In this study, field measurement was carried out in Isawa Dam Reservoir, located in the Kitakami River system in the northern area of Japan, on the flow structure under a thermally stratified condition. The administrator and the local people of the reservoir have concerns about prolonged discharge of higher turbidity water into the downstream, and it is necessary to find solutions to prevention of higher turbidity discharge from the dam. For that purpose, this study made analysis on flow structure in the reservoir that influences on behavior of fine suspended sediment. From the observation results, layered structures of flow velocity were found in the both components of horizontal and vertical velocity. However, the respective components showed different structures and behaviors with each other. We defined “velocline”, which corresponds to a depth at which vertical distribution of the velocity component exhibits apparently large changes. The depth of the velocline of horizontal velocity was close to the thermocline, but vertical displacement was large and frequent. On the other hand, there were two veloclines whose depths were several meters above and below the thermocline, and movement of the veloclines were much smaller than that of horizontal component. In the latter half of the measurement period, scattered velocity variations were observed in the epilimnion, which were presumably caused by the turnover mixing initiated by surface water cooling.

DOI: https://doi.org/10.3850/38WC092019-1559

Year: 2019