State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, 610065, China.
State Key Laboratory of Hydraulics and Mountain River Engineering, Sichuan University, Chengdu, Sichuan, 610065, China.
J Environ Manage. 2024 Jun;360:121155. doi: 10.1016/j.jenvman.2024.121155. Epub 2024 May 17.
The establishment of large hydropower stations in the main stream poses a threat to fish habitats. Selecting suitable tributaries as alternative habitats is a practical measure for ecological environment protection during large hydropower station's construction. The small dams constructed on certain tributaries need to be removed in order to restore river connectivity. The removal of dams will activate hydro-sedimentary dynamics and change the original habitat in terms of topography and hydrodynamics. To explore the evolution of fish habitats following the removal of small dams, a dam-removed reach of a habitat-alternative tributary was selected as the research object, and the model of water-sediment transport and riverbed evolution in strongly disturbed dam-removed reaches and the model of fish habitat suitability evaluation were established. The key parameters calibration and model verification were completed by field monitoring results. The simulation results showed dramatic evolution in the reservoir riverbed in the initial stage after dam removal and during the high discharge period. One year after dam removal, there was a noticeable 4.0 m incision in front of the dam, along with a decrease in channel slope at the dam site from about 4.8% to approximately 1.5%. Downstream of the dam, alterations to the riverbed were mainly concentrated near the dam, and sedimentary bodies with a height of around 2.0 m have formed on the left bank following the high discharge period. The fish habitat in most areas of the dam-removed reach was suitable, except for the downstream high-velocity area. To compare the evolution process of fish habitat under two dam removal periods in wet and dry seasons, two dam removal schemes were implemented in March and June. The results showed that the riverbed evolved more gradually in the March scheme, creating a larger and continuous suitable habitat for fish. Therefore, the March scheme was recommended. By revealing the evolutionary pattern of fish habitat after dam removal, this research provides a reliable model for assessing and restoring habitats in dam-removed reaches, and enjoys significant implications for protecting river ecology in hydropower development reaches.
在主流建设大型水电站会对鱼类栖息地造成威胁。选择合适的支流作为替代栖息地是水电站建设中生态环境保护的一项实用措施。为了恢复河流的连通性，需要拆除某些支流上的小水坝。拆除水坝将激活水沙动力，并改变原有地形和水力条件下的栖息地。为了探索小水坝拆除后鱼类栖息地的演变，选择了一个替代栖息地的支流的拆除段作为研究对象，建立了强干扰拆除段的水沙输移和河床演变模型以及鱼类栖息地适宜性评价模型。通过现场监测结果完成了关键参数校准和模型验证。模拟结果表明，拆除水坝后初期和高流量期水库河床发生了剧烈演变。拆除水坝一年后，在大坝前缘出现了明显的 4.0 米的下切，同时大坝处的河道坡度从约 4.8%降低到约 1.5%。大坝下游的河床变化主要集中在大坝附近，高流量期过后，左岸形成了高度约 2.0 米的沉积体。除下游高速区外，拆除段大部分区域的鱼类栖息地适宜。为了比较湿季和旱季两次拆除水坝对鱼类栖息地演变过程的影响，分别于 3 月和 6 月实施了两次拆除水坝方案。结果表明，3 月方案河床演变更为渐进，为鱼类创造了更大和连续的适宜栖息地。因此，推荐采用 3 月方案。通过揭示拆除水坝后鱼类栖息地的演变模式，本研究为评估和恢复拆除段栖息地提供了可靠的模型，并对保护水电开发河段的河流生态具有重要意义。
