PLUNGING AND STREAMING FLOWS IN POOL-AND-WEIR FISHWAYS

Fishways are river constructions which give a helping to fish migration. The rea re three types of flow formations in pool-and-weir fishways such as a plunging flow, streaming flow and intermixed flow of plunging and streaming flows. Rajaratnam et al. proposed a criterion formula that predicts the flow formations. However, this criterion formula has no physical meaning. Further the accuracy of prediction of their for mula is not high. In this study, the criterion formula, which can predict the flow formation in a pool-and-weir fishway, is derived semi-theoretically. The experiments were conducted with changing the aspect ratio and discharge in the pool-and-weir fishway. The water surface profiles were measured and also three components velocities were measured with a 3-D electromagnetic current meter. A new criterion formula, which is able to predict the flow formation, is proposed under the condition that the channel slope is 1 on 12.