梯级水库的水文累积影响机制及其评估

With the rapid development of cascade reservoirs, the cumulative impacts of hydropower engineering is gradually outstanding. Cascade reservoirs in the river have changed the natural flow regimes which had great effects on river ecosystem. It is a hot topic in the environmental effects in damming rivers that hydrological cumulative effects assessment of cascade hydropower development. And it is an integral part of Environmental Impact Assessment (EIA) in China. Due to the limit of baseline and development of monitoring system, this research is still in the early stage. In fact, hydrological alteration of cascade reservoirs is cumulative response of hydrological factors at different spatial-temporal scales. This study was concentrated on the cascade hydropowers in the upper reach of Yangtze River. It was used mathematical statistics and GIS spatial analysis to analyze the hydrological cumulative effects of cascade reservoirs to typical hydrologic sections in the spawning sites of the upper reach of Yangtze River. Based on the Entropy Theory, it was quantitively assessed the hydrological cumulative effects of cascade hydropower development. And it was also introduced its assessment indicator system.

随着我国梯级水电开发的进程加快，水电工程的累积性影响逐渐突出。梯级水库改变了河流自然水文过程，对河流生态系统结构和功能产生严重影响。重大水利工程的水文累积效应评价是筑坝河流生态效应研究的难点和热点。同时，也是我国现有环境影响评价体系中不可或缺的组成部分。由于受评价参考状态、监测体系建设等限制，目前，该研究尚处于起步阶段。梯级水库对水文过程的改变本质上属于水文要素在时空尺度上累积响应过程。本项目结合我国长江上游地区，采用数理统计方法、GIS空间分析等方法从不同时空尺度上分析梯级水库对长江上游保护区内典型鱼类产卵场的水文累积影响，最终采用基于熵理论的累积影响评价方法，分析梯级水库对河流水文过程的累积影响机制，并提出量化水文累积影响的评价指标体系。

水文是河流生态系统中重要的生境要素。充分认识水情变化规律及其对河流生态系统的累积环境影响机制是流域开发的生态环境累积叠加效应研究的重要基础。本研究以金沙江下游梯级水电工程为对象，基于流域现有的调度规程，构建了通用水库调度模型，采用变化范围法，对比单库运行和水库联合运行对下游水文改变程度，揭示不同水库调度模式下水库联合运行对下游水文情势的累积影响，定量阐明梯级水电工程对水文情势的累积影响机制，提出了年内分布不均匀性表征梯级水库对水文流量累积影响程度，评价梯级水库单库运行前后水文过程的改变。