梯级小水电减水河道的灰线带达标率研究——以大渡河右岸的一级支流Alpha河为例

Research on Gray Line Compliance Rate of Segment of Water Reduction for Cascade Small Hydropower——A Case Study of Alpha river,the Tributary on the Right Bank of Dadu River

河岸带是区域生物多样性的重要孕育地带,对改善水质及河流生态系统的结构与功能有重要作用。然而小水电开发后会产生水面宽度变化,若生态流量下泄不足则会造成生态缓冲带的暴露,对河流水环境、水生生态和陆生生态造成不同程度的影响。本文以Alpha河为例,引入河流灰线带的概念和灰线带变化达标率的评价指标,并建立该指标的评价标准,进而通过计算定量判断Alpha河流域水面宽度变化对生态缓冲带暴露的影响。计算结果显示,Alpha河上参与评价的20座水电站中仅有小水二级电站评价等级为一般,其余电站评价等级均为极差或较差,说明在其流域水电建设运营过程中,生态流量下泄长期不达标,生态缓冲带暴露明显,对当地环境及其生物多样性造成了严重影响。建议有关部门建立小水电退出标准评价体系,退出部分小水电,并加大生态流量下泄,采取相应的纵向连通措施,并加强植被抚育与重建,尽快恢复当地生境。

Riparian zone is an important breeding zone for regional biodiversity.It plays an important role in improving water quality and the structure and function of river ecosystem.However,the development of small hydropower can lead to changes in water surface width.If the ecological flow is insufficient,the ecological buffer zone will be exposed,which will have different impacts on the river water environment,aquatic ecology and terrestrial ecology.Taking Alpha river as an example,this paper introduced the concept of gray line and the evaluation index of gray line changing compliance rate,and established the evaluation standard of this index,then quantitatively evaluated the influence of water surface width change of Alpha river basin on ecological buffer zone exposure.According to the calculation results,among the evaluated 20 hydropower stations on Alpha river,only the secondary hydropower stations of alpha river were rated as average,while the other hydropower stations were rated as extremely poor,indicating that during the construction and operation of the river basin,the ecological flow was not up to the standard for a long time,and the ecological buffer zone was exposed obviously,which had caused serious impact on the local environment and biodiversity.It is suggested that the relevant departments should establish a standard evaluation system for the withdrawal of small hydropower stations to withdraw some small hydropower stations and increase the discharge of ecological flow.In addition,relevant departments should adopt corresponding longitudinal communication measures,strengthen vegetation cultivation and reconstruction,and restore local habitats as soon as possible.