基于河流生境调查的东河河流生境评价

河流生境是河流生态系统的重要组成部分,是河流生物赖以生存的基础。以位于三峡库区腹心区域的典型山区河流东河为研究对象,采用河流生境调查(RHS)方法调查河流生境,选择河流生境质量评价指数(HQA)、河流生境退化指数(HMS)评估河流生境现状,分析生境质量和人为干扰的空间分布规律。结果表明,51个河段的HQA值介于24—66之间。29.4%河段的HQA为优,29.4%为良,23.5%为中,9.8%为较差,7.8%为差。从HMS看,7.8%的河段保持较自然状态,19.6%受到轻微的破坏,41.2%退化明显,27.5%退化严重,3.9%受到剧烈破坏。HQA与HMS存在显著的负相关关系。东河上、中、下游河段的HQA无明显差异,但HMS差异显著。从干扰来源看,东河上游和中游河流生境主要受引水式小水电、沿河公路、河道采砂影响。东河下游河流生境受高强度的土地开发(农业用地、建设用地),河道采砂,河堤、排污管、桥梁等水工构筑物的修建和三峡水库水位的波动影响。RHS评价结果能较直观地反映河流生境状况,以及导致河流生境质量衰退的原因。

Stream habitat assessment of Dong River, China, using River Habitat Survey method

River habitat is an important component of river ecosystem and also the foundation of existence and development riverine organisms. Recently, the survey and assessment of river habitat plays an increasingly important role in watershed ecological planning, river environmental impact assessment and river ecological restoration. River Habitat Survey is a methodology for recording habitat features for river habitat, designed by the Environment Agency, England and Wales since 1992. Nowadays, River Habitat Survey is being used as a standard methodology for assessing hydromorphology which is a part of the European Water Framework Directive and also as a tool for monitoring river habitats and assessing potential impacts of developments. As a famous stream physical habitat assessment method, River Habitat Survey was wildly applied in many other countries beside Europe countries. In order to introduce River Habitat Survey to Chinese scientist and promote river habitat assessment work in China, Dong River located in the Three Gorges Area of China was investigated using River Habitat Survey method to evaluate its habitat quality and identify dominant human disturbances. Both Habitat Quality Assessment and Habitat Modification Score were employed to assess its status and spatial pattern of human disturbance. In April, 2011, fifty one river reaches of the Dong River were investigated. The result indicated that the Habitat Quality Assessment score ranged from 24 to 66. The reaches with "excellent" Habitat Quality Assessment score was 29.4%, 29.4% "good", 23.5% "fair", 9.8% "poor" and 7.8% "extremely poor". According to Habitat Modification Score, 7.8% of reaches is semi-natural status, 19.6% of predominantly unmodified status, 41.2% of obviously modified status, 27.5% of significantly modified status and 3.9% of severely modified status. Habitat Quality Assessment score was significantly negative correlated with Habitat Modification Score. Habitat Quality Assessment score of upstream, midstream and downstream of the Dong River was not significantly different, while four assessment categories, including channel features, in-stream channel vegetation, land-use within 50 m and trees and associated features, were significantly different. Habitat Modification Score of downstream reaches were significantly different between those of upstream and midstream reaches. The river habitat of upstream and midstream reaches of the Dong River was mainly influenced by small hydropowers, highways along river and sand excavation in river channel, while the river habitat of downstream river reaches was significantly affected by intensive land exploration, sand excavation in river channel, construction of riverbank, drain pipe, bridge and water level fluctuation of the Three Gorges Reservoir. Our research suggested that River Habitat Survey can efficiently detect the status of river habitats and find the dominant reasons for its deterioration.