龙羊峡水库对下游水沙条件变化的影响分析

为了研究龙羊峡水库对下游水沙条件变化的影响,以水库下游贵德水文站年径流量和年输沙量作为研究数据,采用互补集合经验模态分解方法对建库前后径流和泥沙进行多时间尺度分析,结合多时间尺度熵和纳什效率系数分析建库前后径流和泥沙各分解序列的复杂波动特征及各分量对原始序列的贡献程度。结果表明:水库运行对下游水沙变化均有显著影响,且对泥沙的影响大于径流,同时不同时间尺度下的水沙相关关系均发生改变;水库运行会加剧水沙系统的复杂性,但随着多时间尺度波动周期的增大,水沙各分解序列复杂性降低,可预测性升高;径流和泥沙的信息量集中在中高频分量上,综合考虑建库前后水沙波动周期的变化,建议黄河上游水沙监测和研究周期分别为4~7 a和3~4 a。

An Analysis of the Impact of the Longyangxia Reservoir on the Variation of Runoff and Sediment Load Conditions Downstream

In order to study the impact of the Longyangxia Reservoir on the variation of downstream runoff and sediment load conditions,the annual runoff and annual sediment load at the Guide Hydrological Station downstream of the reservoir are taken as the research data,and the complementary ensemble empirical mode decomposition method is used to analyze the runoff and sediment load at multi-time scales before and after the reservoir construction.Based on the multi-time scale entropy and Nash-Sutcliffe efficiency co-efficient the complex fluctuation characteristics of the runoff and sediment load decomposition sequences are analyzed before and after the reservoir construction and the contribution of each component to the original sequence.The results show that the reservoir operation has a significant impact on the variation of runoff and sediment load downstream of the reservoir,and the impact on sediment load is greater than that of runoff,and the correlation between runoff and sediment load changes at different time scales.The reservoir operation will aggravate the complexity of the runoff and sediment load system.However,with the increase in the multi-time scale fluctuation period,the complexity of runoff and sediment load decomposition sequence decreases and the predictability increases.The information content of runoff and sediment load is concentrated on the medium and high frequency components,and the periodic variation of runoff and sediment load fluctuations before and after the reservoir construction are considered comprehensively.It is recommended that the monitoring and research periods of runoff and sediment load in the upper reaches of the Yellow River should be 4~7 years and 3~4 years respectively.