Design of a Novel Multislot and Pool–Weir Combined Fishway Based on Hydraulic Properties Analysis and Fish-Passage Experiments

Abstract

A brand-new type of multislot and pool–weir combined fishway (MSWF) is firstly proposed in this paper. In fact, six MSWF configurations (MSWF-1 to MSWF-6) are designed and compared, and numerical results demonstrate that MSWF-5 (i.e., weir height h=0.6 m and the vertical-slot width bs=0.62 m) has the best performance at a flow discharge (i.e., Q) of 600 L/s in terms of flow topology, velocity distribution, and turbulent kinetic energy among all the eight fishways considered. The introduction of the weir in MSWF not only contributes to improving the flow regime, but also offers an extra fish-passage channel for fishes. Moreover, the general superiority of MSWF-5 over the vertical-slot fishway (VSF) is exhibited by providing the numerical results at Q=600, 800, 1,000, and 1,200 L/s. Additionally, fish-passage tests are carried out in a physical model (including the MSWF-5 part and the VSF part) with the aid of juvenile grass carps. As expected, the recommended MSWF-5 does outperform VSF with respect to passage success rate, mean fish transit time, entry efficiency, and mean entrance time, matching its excellent hydraulic properties.