梯级水坝对高原河流健康的影响研究

为分析梯级水坝对高原河流健康的影响，考虑高原河流特征和国内外研究成果，构建了基于水文、水质、水生态3个准则层、12个指标的健康评价指标体系，采用模糊综合健康评价模型评价筑坝河段的健康水平．结果显示:1）梯级水坝剧烈改变了筑坝河段的水文和水质特征，筑坝后河水流速和DO分别平均下降75%和12%，水深和水温平均上升了67%和50%．2）连续筑坝区域水质中COD_Mn和BOD指标分别下降28%和21%，水体沉积物中TN、TP和TOC平均上升为40%、23%和64%．3）水文和水质的变化改变筑坝河段水体浮游生物的生长环境，浮游植物和浮游动物的种群结构发生显著变化，浮游生物的种类、密度和生物量平均上升1.7、71和12倍．4）从时空尺度看，梯级水坝对枯水期河流的影响较平水期和丰水期高78%，对上段筑坝区的影响较下段筑坝区平均高56%．小型梯级水坝对湟水河段河流健康产生影响较大，亟需长期的监测和系统的评估． 

Cascade dams affect river health in plateau regions:a case of Huangshui River

Impact of cascade dams on the health of plateau rivers, such as Huangshui River in Qinghai, was analyzed with an index of 12 indicators at the level of hydrology, aquatic ecology, and water ecology．With natural rivers as reference for evaluation criteria, the fuzzy comprehensive health evaluation model was used．Cascade dams were found to drastically change hydrological and water quality characteristics in the damming river section．After damming, river flow velocity and DO decreased by an average of 75% and 12%, respectively, but water depth and water temperature increased by an average of 67% and 50%．COD_Mn and BOD indicators in continuous damming areas were found to have decreased by 28% and 21%, respectively．Average TN, TP and TOC increases in water sediments were found to be 40%, 23% and 64%．Changes in hydrology and water quality led to changes in the growth environment of plankton in damming rivers, population structure of phytoplankton and zooplankton underwent significant changes．Types, density and biomass of plankton were found to have increased by 1.7 times, 71 times and 12 times on average．Effect of cascade dams on rivers in dry seasons was found to be 78% higher than in normal and high water periods．Impact on upper dam area was 56% higher than downstream dam area．Small cascade dams were found to have greater impact．We suggest that long-term monitoring and systematic evaluation are urgently needed．