Abstract Many large-scale southwestern mountain rivers have intensive hydropower development in China, and it is difficult for the mainstream habitats to meet the needs of fish; thus, the replacement of tributary habitats has become an effective measure for river ecological protection. Appropriate ecological flow is an important tool used to repair fish habitats and plays an important role in the ecological protection of tributaries, but this practice has caused conflicts with the economic interests of hydropower owners, which has made the implementation of restoration work more difficult; therefore, it is imperative to ease the contradiction between the two. Based on field investigation and monitoring, this paper designs remedial measures for the horizontal and vertical sections of the river section, namely, dredging the river horizontally and constructing a water-retaining weir and underwater dam vertically. A two-dimensional hydrodynamic model was used to numerically simulate the hydrodynamic conditions before and after different ecological restoration measures, and the corresponding weighted usable area (WUA) was calculated to evaluate the different restoration effects on habitats. The results show that the suitable ecological flow rate of the study section is 16.80 m3/s (35% average annual flow), and the WUA increased by 317.37% compared with the initial state of 2.39 m3/s (5% average annual flow); when discharge flow is 4.80 m3/s (10% average annual flow), the improvement measures of habitat quality include the combination of river dredging and the construction of water-retaining weir, construction of water-retaining weir, construction of underwater dam, and river dredging. The initial state increased by 129.96%, 177.19%, 226.51% and 329.21%, respectively. The partial excavation and dredging have a complementary effect with the construction of the water trap, and the increase in the WUA caused by the combination of the two exceeds the increase caused by the appropriate ecological flow. In summary, targeted restoration measures can achieve the goal of maintaining a high level of habitat quality at lower flow levels.

中文翻译：

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中小流量山地河流鱼类栖息地质量维持研究

摘要 我国西南山区许多大型河流水电开发密集，主流栖息地难以满足鱼类的需求；因此，更换支流栖息地已成为河流生态保护的有效措施。适宜的生态流量是修复鱼类栖息地的重要工具，在支流生态保护中发挥着重要作用，但这种做法与水电业主的经济利益产生了冲突，使得修复工作的实施难度加大；因此，缓和两者之间的矛盾势在必行。本文在实地调查和监测的基础上，设计了河段水平段和垂直段的补救措施，即：横向疏浚河流，纵向修建挡水堰和水下大坝。利用二维水动力模型对不同生态恢复措施前后的水动力条件进行数值模拟，计算相应的加权可用面积(WUA)，评价不同的生境恢复效果。结果表明，研究断面适宜生态流量为16.80 m3/s（年均流量35%），用水户协会比初始状态2.39 m3/s（年均流量5%）增加了317.37% ; 当排放流量为4.80 m3/s（10%年均流量）时，生境质量改善措施包括河道疏浚与修建挡水堰相结合，修建挡水堰，水下大坝建设，河道疏浚。初始状态分别增加了129.96%、177.19%、226.51%和329.21%。局部开挖和疏浚与集水器的建设具有互补作用，两者结合引起的用水户协会增加超过了适当生态流量引起的增加。总之，有针对性的恢复措施可以实现在较低流量水平下保持高水平栖息地质量的目标。