小浪底水库运用后黄河下游水沙变化及河道冲淤演变

发布时间：2019-01-09 19:19

【摘要】：水库的修建显著改变了进入下游河道的水沙条件,对下游河道演变也具有显著影响。小浪底水库是黄河干流最靠近下游的一座水库,控制着进入黄河下游河道的水沙过程。经过多年的初期运用,小浪底水库在减少水库下游河道淤积和稳定合适的中水河槽规模发挥了重要作用。本文以小浪底水库为例,分析了小浪底水库初期运用以来黄河下游水沙变化及河道冲淤演变过程,并研究了下游河道演变与水沙过程的响应。本文主要研究成果总结如下:(1)小浪底水库运用后15年内,下游水量年内分配发生明显改变,汛期来水量比重明显小于非汛期,下泄沙量明显减少。调水调沙期间,水库最大下泄流量形成平头洪峰,中水流量持续的时间增加;水沙趋势分析表明,黄河下游来水来沙量在1950～2015近65年整体呈显著减小趋势,小浪底水库运用后,年径流量变化趋势趋于稳定,年输沙量呈显著降低趋势;通过水沙多时间尺度分析,花园口站年径流量、输沙量变化分别以22a和9a尺度为首要主周期。黄河下游花园口站水沙序列的周期规律与中游潼关站基本一致,小浪底水库(联合三门峡水库)运用对下游水沙序列多时间尺度特性影响不大。(2)统计分析了小浪底水库运用及调水调沙期间黄河下游河道冲淤特点,分析了河道横断面形态调整及断面特征参数、平滩流量的演变过程。结果表明:小浪底水库运用后黄河下游河道均保持相对稳定的冲刷。18次调水调沙冲刷量仅占下游总冲刷量的14.69%,不是下游冲刷的主体,2007年后调水调沙冲刷效率逐渐降低;小浪底水库运用后,各典型河段横断面均以冲刷下切为主,局部河段伴有横向展宽;小浪底水库运用后,平滩流量有一定回升,2007年底黄河下游四站均值已恢复到了 4000m3/s以上。(3)运用回归分析(含逐步回归)、BP神经网络研究了黄河下游平滩面积、平滩流量与水沙条件的响应关系。结果表明:平滩面积、平滩流量受前期水沙因子的影响时间大致为4～6年。考虑流量和来沙系数两个主要因子,以5年滑动平均值拟合出平滩流量与两个因子的相关性公式,基本能反映平滩流量随水沙条件的年际变化过程;考虑平滩流量的多个影响因子,基于逐步回归方法和BP神经网络模型建立了平滩流量的预测模型,就总体预测精度而言,BP神经网络逐步回归模型汛期水沙拟合模型,但BPyL经网络对于平滩流量极值点的预测效果较差,需要更大范围数据的训练。
[Abstract]:The construction of reservoir has changed the condition of water and sediment entering the downstream channel and has a significant influence on the evolution of the downstream channel. Xiaolangdi Reservoir is a reservoir closest to the lower reaches of the Yellow River, which controls the process of water and sediment entering the lower Yellow River. After many years of initial application, Xiaolangdi Reservoir plays an important role in reducing the deposition of the lower reaches of the reservoir and stabilizing the appropriate scale of the middle water channel. Taking Xiaolangdi Reservoir as an example, this paper analyzes the variation of water and sediment in the lower reaches of the Yellow River and the evolution process of channel erosion and siltation since the initial operation of Xiaolangdi Reservoir, and studies the response of the evolution of the lower reaches of the river and the process of water and sediment. The main research results of this paper are summarized as follows: (1) within 15 years after the operation of Xiaolangdi Reservoir, the annual distribution of downstream water volume has changed obviously, the proportion of incoming water in flood season is obviously smaller than that in non-flood season, and the amount of sediment discharge is obviously reduced. During the period of water and sediment regulation, the maximum discharge of the reservoir formed flat head Hong Feng, and the duration of the middle water flow increased. The analysis of water and sediment trend shows that the amount of incoming water and sediment from the lower reaches of the Yellow River decreased significantly in the last 65 years from 1950 to 2015. After the operation of Xiaolangdi Reservoir, the change trend of annual runoff tended to be stable and the annual sediment discharge decreased significantly. Based on the analysis of multi-time scale of water and sediment, the annual runoff and sediment discharge of Huayuankou Station are mainly controlled by the scale of 22a and 9a, respectively. The periodicity of water and sediment sequence of Huayuankou station in the lower reaches of the Yellow River is basically the same as that of Tongguan station in the middle reaches of the Yellow River. The use of Xiaolangdi Reservoir (United Sanmenxia Reservoir) has little effect on the multi-time scale characteristics of the downstream water and sediment sequence. (2) the characteristics of the channel scouring and silting in the lower Yellow River during the operation and the water and sediment transfer of the Xiaolangdi Reservoir are analyzed statistically. The course of river channel cross section shape adjustment, section characteristic parameter and flat discharge evolution is analyzed. The results show that after the operation of Xiaolangdi Reservoir, the channel of the lower reaches of the Yellow River keeps relatively stable scour, and the amount of 18 times of water and sediment transfer only accounts for 14.69% of the total amount of the downstream scour, which is not the main part of the downstream scour. After 2007, the efficiency of water and sediment transfer and erosion gradually decreased; After the operation of Xiaolangdi Reservoir, the cross section of each typical reach is mainly cut down by scouring, and the local reach is accompanied by transverse widening. After the operation of Xiaolangdi Reservoir, the flat discharge has recovered to a certain extent, and the mean value of the four stations in the lower Yellow River has recovered above 4000m3/s at the end of 2007. (3) the flat area of the lower Yellow River has been studied by means of regression analysis (including stepwise regression), BP neural network). Response relationship between flat discharge and water and sediment conditions. The results show that the area and discharge of flat beach are affected by the factors of water and sediment in the early stage, and the influence time is about 4 ~ 6 years. Considering the two main factors of discharge and sediment supply coefficient, the correlation formula of flat beach discharge and two factors is fitted by the 5-year sliding average value, which can basically reflect the interannual variation process of flat beach discharge with water and sediment conditions. Based on the stepwise regression method and the BP neural network model, the prediction model of flat beach discharge is established considering several influencing factors of flat flow. In terms of the overall prediction accuracy, the BP neural network stepwise regression model is used to fit the water and sediment in flood season. However, the prediction effect of BPyL network for the maximum point of flat flow is poor, and the training of larger range of data is needed.
【学位授予单位】：中国水利水电科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV147

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