三峡水库对下游河流水沙情势影响评估

The Assessment of the Impact of Three Gorges Reservoir on Runoff and Sediment in the Lower Reaches

为了评价三峡水库蓄水后下游河流水沙情势变化特征及其产生的生态影响,运用双累积曲线法、MannKendall趋势检验法和变动范围法(RVA)对三峡水库下游宜昌站1952-2015年逐日流量和含沙量指标进行探究。分析结果表明:三峡水库下游河流水沙特性在2003年发生明显转折,年均流量和含沙量均显著下降;月均流量在丰水期增加,枯水期减少,月均含沙量年内大幅下降;年最小1、3、7、30、90日流量发生高度改变,而年极值含沙量各指标改变度均达到100%;流量脉冲基本属于低度改变,含沙量高脉冲改变度达到100%;流量的逆转次数,含沙量的上升率、下降率和逆转次数均发生高度改变;通过对河流水沙情势改变度评价,其流量属于中度改变,含沙量属于高度改变。三峡水库蓄水后在一定程度上改变了下游河流的水沙情势,对河流生态系统健康带来一定影响。研究结果可为三峡水库下游河流生态保护提供参考。

To assess flow and sediment alternation and influence in the lower reaches of Three Gorges Reservoir,runoff and sediment during the period from 1952 to 2015 at the Yichang station are evaluated by using the double cumulative curve analysis method,the Mann-Kendall statistical test and the range of variability approach.The results show that the double cumulative curve witnessed a marked turnaround in2003,and the annual average flow and sediment concentration showed a significant downward trend.The monthly flow increases during the period of wet season and decreased during the dry season.The monthly sediment decreases significantly.The annual 1,3,7,30,90 day minima flows reached high alteration,and the annual extreme indicators of sediment reaches high alteration,with alteration of 100%.The pulses of flow are low alteration mainly,but the high pulses of sediment reach high alteration,with alteration of 100%.The reveals of flow and sediment,the fall rate and rise rate of sediment fall in high alteration.Those changes would have a profound impact on the ecology in the basin.The runoff and sediment situation have been changed after the impoundment of the Three Gorges Reservoir,causing some impacts on the river ecosystem health in the lower Yangtze River.The study provides a scientific reference for the ecological protection in the lower reaches of the Three Gorges Reservoir.