Author(s): Guangning Li, Shuangke Sun
Linked Author(s): Guangning LI
Keywords: Water level, variation, vertical slot fishway, fishway entrance, hydraulic model test
Abstract: The large variation of downstream water level is a big challenge for the design of fishway entrances. The normal fishway entrance is only suitable for a limited range of water level variation (0. 5~1. 0m). When the variation is larger, more entrances should be set up at different elevations along the downstream river, and separated in an expanse range. It is conflicted with the aggregation habit of the migratory fishes. The fishes are usually aggregated in a relatively small area in the tailrace channel and near to the dam. In addition, the flow fields of the entrances location away from the tailrace channel are always not suitable for the fish aggregation. Therefore the entrances will be inefficient. The frequent switching the gates of the entrances are fussy operations and the project site conditions for arranging multi entrances have been confronted with many difficulties. In this paper, a compact self-adapting fishway entrance without gate for the large variation of downstream water level is proposed. The entrance is designed based on the law of the water depths change in the Vertical Slot Fishway (VSF). The entrance contains several parallel connected returning sections of VSF, and each returning section has its own opening to the river. Each opening has a specific bottom elevation, and the bottom of the opening is higher than the inner pool. When the water level in the adjacent pool is lower than the bottom of the opening, the water will moved to the next inner pool normally. When the water depth in the pool is higher than the bottom of the opening, the water can flow out into the river, and forms a flow with proper velocity to attract fishes. The flow split ratios, flow patterns and velocity profiles of the openings under different scenarios were studied by hydraulic model tests. All the test results have proved that the opening will act as the main fish entrance when the downstream water level is higher than the bottom elevation within a certain range. The fishway entrance is compact, self-adapting and suitable for the large downstream water level variation when the openings bottom elevations are designed properly
Year: 2017