荆江三口分流变化贡献率及其对三峡水库调度响应

Contribution Rate for the Change of Diversion through the Three Outlets and Its Response to the Three Gorges Reservoir Operation

为系统评估三峡水库调度对三口分流过程的影响,基于大量的原观数据,依据控制变量思想,通过对比分析及径流还原的方法,定量计算了三峡水库运行前后三口分流量减幅与各单一影响因子的贡献率。结果表明:(1)无论水库调度与否,天然来流都是分流量减少的首要因素。三峡水库运行以来,枝城站2003-2008年与2009-2015年平均径流量分别为4 064、4 128亿m3,远低于水库运行前的4 453亿m3,超过60%的分流量减少都是天然来流偏枯所致。(2)三峡水库优化调度后,随着蓄水时间提前与起蓄水位提高,三口分流量进一步减少。2003-2008年,天然来流、水库调度、河床冲刷在分流量减少过程中贡献率分别为76.19%、10.32%、13.49%;而2009-2015年,三者贡献率分别为66.05%、19.75%、14.20%。

To evaluate the influences of the operation of TGR on the diversion process of the three outlets,this paper investigates systematically the variation process of the runoff at the three outlets based on substantially raw data and principles of variable control.Specifically,by employing the comparative analysis and the calculation method of runoff reduction,it quantifies the changing magnitude of the runoff at the three outlets and also estimates the contribution rate of different factors in different periods after the implementation of TGR 's operation.It is demonstrated that ① inflow difference from Yangtze River is the primary factor causing the runoff reduction of the three outlets.After the operation of TGR,the Yangtze River was in dry years.The annual averaged runoff at Zhicheng Station from 2003-2008 and 2009-2015 are respectively 4 064 ×10^8 and 4 128 ×10^8 m^3,which are significantly smaller than their counterpart before the operation of TGR ( 4 453 ×10^8 m^3 ) .Therefore,over 60% of runoff reduction can be attributed to the variation of natural inflow discharge.② As the flow is retained by the TGR,as the advance of impounding time and improvement of impounded level,the runoff of the three outlets further reduced.From 2003-2008,the contribution rates of natural flow,reservoir regulation and sediment trapping to the runoff reduction at the three outlets were 76.19%,10.32%,13.49%,while their counterparts after optimal operation of TGR became 60.05%,19.75%,14.20% respectively.