三峡工程运行后长江中下游河道设计频率水文年泥沙模拟研究

三峡水库运行以来,长江水沙发生很大的变化,为今后泥沙模型计算与试验水文条件的仿真性提供保证和依据,统计分析了三峡水库建库以来长江中下游泥沙的变化情况,并针对泥沙模型计算与试验中常选取的频率水文年的泥沙问题,做了详细的分析与研究。提出了泥沙模型中设计频率水文年所要模拟的沙质泥沙部分的处理方法与途径,即床沙质的输沙率过程采用流量输沙率关系推求设计洪水对应的沙量过程。并出于工程安全的考虑,采用流量输沙率关系的下包线作为沙量过程确定的依据。该方法较好地反映了三峡水库蓄水后泥沙量减少条件下的频率水文年泥沙模拟实际情况。

Study on the Simulation of Sediment in Hydrological Year of Designed Frequency in the Middle-Lower Reaches of Yangtze River after the Three Gorges Project Operation

The water flow and sediment in Yangtze River have changed remarkably since the operation of Three Gor-ges Reservoir.To provide guarantee and basis for the simulation of hydrological conditions in sediment model calcu-lation,we statistically analysed the variation of sediment in the middle-lower Yangtze River since the Three Gorges Reservoir impoundment.On this basis,we carried out detailed research on the sediment problem of hydrological year of designed frequency which is often selected in sediment model calculations and tests.We proposed the meth-od and approach of dealing with sandy sediment in sediment model which is to deduce the sediment process of de-signed flood according to the relationship between flow rate and sediment transport rate.Moreover,in consideration of project safety,we proposed to take the lower enveloping curve of flow rate versus sediment transport rate as the basis of determining sediment process.Through this method,the sediment condition in hydrological year of de-signed frequency when sediment load decreases could be well reflected.