Abstract
Bypass tunnel is one of the important water quality management facilities in reservoirs. There are two types of bypass tunnels. One is bypassing turbid water and the other is bypassing clear water to the downstream of a reservoir. However, these systems are quite new and we do not have sufficient information. In order to evaluate the effect of bypassing of clear water on water quality both in reservoir and downstream, we applied a three-dimensional water quality simulation model, ELCOM-CAEDYM developed by CWR, to Urayama reservoir in Arakawa River basin. The comparison of the model results between an actual bypass operation and a scenario without bypass operation showed that the bypass operation has improved SS in downstream of the reservoir remarkably. Moreover it revealed that the bypass has improved other water quality parameters not only in downstream but also in reservoir.
