近20年三峡水库坝下水沙情势变化特征及趋势分析——以黄陵庙水文站为例

Characteristics and Variation Trends of Flow Rates and Sediment Concentra-tions Downstream of the Three Gorges Dam in the recent 20 years——A Case Study on Huangling Temple Hydrological Station

基于1996-2014年黄陵庙水文站流量与含沙量数据,对三峡水库坝下流量及含沙量年内与年际变化特征、相关关系与变化趋势进行了初步分析。研究发现,1996-2014年黄陵庙水文站流量峰值以每年610 m3·s-1的速度下降(P<0.05),谷值平均以每年146 m3·s-1的速度上升(P<0.01),蓄水后全年平均流量下降了8.0%。全年平均含沙量在蓄水后减少了90.0%,受到三峡工程施工与蓄水的影响,含沙量在研究时间段内先增加后减小,呈二次指数变化规律(P<0.01)。蓄水前流量与含沙量月均值呈线性关系(P<0.01),Pearson相关系数为0.941(P<0.01),蓄水后呈指数型关系(P<0.01),相关系数为0.766(P<0.01)。GM(1,1)模型预测结果显示,2016-2025年均流量下降率为2.0%,模型平均误差率为0.091;年均含沙量下降率为34.6%,模型平均误差率为0.179。

The construction and operation of the Three Gorges Project has weakened the adverse effects of uneven temporal and spatial distribution of the Yangtze River Runoff. But at the same time, the conditions and trends of water and sediment downstream of the dam have also changed. Based on the monthly averaged flow rates and sediment concentrations observed downstream of the dam in Huangling Temple hydrological station during 1996-2014,their characteristics, correlations, and change trends were investigated in this paper with statistical analysis and mathematical modeling method. The study indicates that:(1) The flow rates and sediment concentrations observed in Huangling Temple were high in summer, and low in winter.(2) The yearly peak values of the flow rates decreased at the rate of 610 m3·s-1per year(P<0.05), and the yearly valley values increased at the rate of 146 m3·s-1per year(P<0.01). After the impoundment, the annually averaged flow rates decreased by 8.0%.(3) The annual sediment concentrations decreased by 90.0% after impoundment. Affected by the construction and impoundment of theThree Gorges Project, the annually averaged sediment concentrations followed the exponential law of a second order function of time.(4) There was a linear and exponential relationship between the monthly averaged flow rates and sediment concentrations before and after the impoundment, respectively.(5) As predicted by the GM(1,1) model,both the annually averaged flow and the sediment concentrations showed a trend of decline.(6) Scientifically and reasonably dispatching of the reservoir water flow can improve the sediment transport efficiency, ease the reservoir sedimentation, and reduce the downstream river erosion intensity.