水电梯级开发对河流生境质量及纵向连通性影响评价——以五布河和藻渡河为例

河流物理生境是维持河流生物多样性及生态功能的关键因素。生境质量的好坏能反应河流健康的程度。以我国西南地区的五布河和藻渡河为例,采用河流生境调查方法(RHS)和树状水系连通性指数(DCI)定量评估水电梯级开发和水坝建设对河流物理生境质量和河流纵向连通性的影响。结果表明,水电梯级开发后,五布河干流未受水坝明显影响河段、库区河段、减水河段分别为20.48、43.34、18.09 km,占总长度的25.0%、52.9%、22.1%。藻渡河干流河口至双河口段未受水坝明显影响河段、库区河段、减水河段分别为58.61、8.28、18.99 km,占总长度的68.2%、9.6%、占22.1%。水电梯级开发后,五布河干流河流片段由26个增至29个,藻渡河干流河流片段由2个增至5个。两条河流纵向连通性分别降低了7.8%和38.0%。五布河坝下减水河段生境质量降低14.1%,库区河段生境质量变化不明显。藻渡河减水河段生境质量与近自然河段无显著差异;两座坝后式电站库区河段生境质量明显低于近自然河段。水电梯级开发对两条河流物理生境的影响与水坝位置选择、建坝前的自然阻隔数量与分布、河流地貌特征、水电资源开发方式等密切相关。

Assessment method for the influence of hydroelectric dams on the physical habitat quality and longitudinal connectivity of rivers: a case study of the Wubu and Zaodu rivers

Physical habitats of rivers are important factor to maintain fluvial ecosystem biodiversity and ecological functions. Habitats quality can reflect the status of river health. To evaluate the influence of watershed hydropower development and associated dam construction on the Wubu and Zaodu rivers in Southwest China, River Habitat Survey (RHS) and Dendritic Connectivity Index (DCI) were used to assess the river physical habitat quality and longitudinal connectivity. The results indicated that the length of near-natural, reservoir, and water-reduced reaches on the Wubu River were 20.48, 43.34, 18.09 km, which were 25.0%, 52.9%, and 22.1% of its entire main stream, respectively. The length of near-natural, reservoir, and water-reduced reaches on the Zaodu River were 58.61, 8.28, and 18.99 km, which were 57.5%, 8.1%, and 18.6% of its entire main stream, respectively. As a result of watershed hydropower development, river segments of the Wubu River increased from 26 to 29 reaches and those of the Zaodu River increased from two to five reaches. The DCI of the two rivers decreased by 7.8% and 38.0%, respectively. Habitat Quality Assessment (HQA) of the water-reduced reaches on the Wubu River decreased by 14.1%, whereas that of reservoir reaches was not significantly influenced by watershed hydropower development. The HQA of water-reduced and near-natural reaches on the Zaodu River were not significantly different. The HQA of reservoir reaches on the Zaodu River behind two high dams were significantly different from near-natural reaches. The influence of watershed hydropower development and associated dam construction on the physical habitat of the two rivers was associated with dam location, number and distribution of river segments before dam construction, fluvial geomorphological character, and hydropower resources exploration methods.