三门峡水库时空冲淤与滞后响应

Spatial and temporal erosion and deposition processes and the delayed response of the Sanmenxia reservoir

基于三门峡水库1960-2016年水沙和冲淤资料,本文分析了水库纵向与横向、年内与年际、时间与空间上的冲淤演变规律。结果表明:三门峡水库的冲淤过程可大致分为1960-1969年快速淤积、1970-1973年快速冲刷、1974-2002年缓慢淤积和2003-2016缓慢冲刷4个阶段;库区冲淤是上游来水来沙与下游水库运用协同作用的结果,1974年水库蓄清排浑运用前,主要受水库运用引起的溯源冲淤的影响,之后水沙作用增强。溯源冲淤向上游传播过程中冲淤幅度逐渐减小,溯源冲刷的影响时间相对较短,而溯源淤积的影响时长向上游不断延长,上游回水区河道溯源淤积累计量达到最大值的时间明显滞后于库区河道,当库水位开始下降及库区河道开始冲刷时,上游回水区仍可处于溯源淤积的影响之下。改进了河床演变的滞后响应模型,得到了权重归一化的滞后响应模型,克服了原有模型中特征量平衡值的权重之和小于1而可能对平衡值进行偏大估计的缺点。采用改进后的模型建立了三门峡水库累计淤积量的计算方法,该方法可较好模拟三门峡水库蓄清排浑运用以来的冲淤演变过程,计算精度较高。

Based on the data of water discharge,sediment load and channel erosion and deposition from1960-2016,we analyzed channel longitudinal and lateral adjustment in the reservoir,inter-annual channel evolution and that within years,and spatial and temporal evolution characteristics. The results showed that channel evolution in the reservoir was characterized by four phases:1960-1969 rapid aggradation,1970-1973 rapid erosion,1974-2002 slow aggradation,and 2003-2016 slow erosion. Channel evolution in the reservoir was the result of the coupled impacts of the upstream water and sediment inflow and downstream dam operation. Before the reservoir was operated by‘storing the clear water and discharging the turbid’in1974,the channel upstream of the dam was mainly impacted by the retrogressive erosion and deposition,the impacts of water and sediment conditions increased relatively thereafter. As the retrogressive erosion and deposition waves propagated upstream,their amplitudes decayed. The impact time length of the retrogressive deposition wave increased as the wave propagated upstream while that of the retrogressive erosion wave was relatively short. Retrogressive aggradation occurred later at the upstream backwater channel,and the cumulative volume of sediment deposition reached its maximum value obviously later than that in the channel in the reservoir. When pool level started to drop and reservoir channel was eroded,the upstream backwater channel may still be impacted by the retrogressive aggradation. In this study,we improved the existing Delayed Response Model(DRM) by normalizing the weights for the equilibrium values of a simulated morphologic variable of the fluvial system. The improved model avoids the disadvantage that the sum of the weights is less than unit and the equilibrium values of the simulated variable may be over-estimated. The improved model was used to develop a calculation method for the cumulative deposition volume in the Sanmenxia reservoir. The proposed calculation method could well simulate the long-term erosion and deposition processes.