小浪底水库运用以来黄河下游河道冲淤的时空规律与模拟

Temporal and spatial laws and simulations of erosion and deposition in the Lower Yellow River since the operation of the Xiaolangdi Reservoir

1999年小浪底水库投入运用以来,黄河下游河道发生持续冲刷,其时空变化过程复杂。基于滞后响应模型单步模式推导得到了黄河下游累计冲淤量的计算公式,2000—2020年计算值与实测值之间的决定系数R2达0.99。当前,黄河下游处于持续冲刷之中,冲刷速度逐渐变慢,当前时段的平衡值与计算值的差异减小,河床冲刷正在逐渐趋向于平衡。基于悬移质泥沙不平衡输沙方程得到了黄河下游主槽单位河长累计冲刷量空间分布的计算公式,2003—2015年计算值与实测值之间的决定系数R2在0.98~0.99之间,相对误差多年平均值为6.2%。结果表明,在当前黄河下游来沙减少,河道发生持续冲刷的背景下,就多年平均情况而言,累计淤积量调整完成一半所需的时间约为3.0 a,完成95%所需的时间约为13.0 a;且随着冲刷的持续发展,黄河下游累计冲刷量的空间分布在逐渐趋于均匀。本文的结果可为分析黄河下游复杂时空变化过程提供参考。

This study focuses on the Lower Yellow River(LYR),which has experienced continuous erosion since the operation of Xiaolangdi Reservoir in 1999,and its complex spatiotemporal variation process.Using the single-step mode of the Delayed Response Model(DRM),we derive a calculation formula for the accumulated erosion and deposition volume in the LYR.The coefficient of determination R2 between the simulated and observed values from 2000 to 2020 is 0.99.Currently,the LYR is undergoing continuous erosion,but the erosion rate is gradually slowing down,and the difference between the equilibrium value and the calculated value of accumulated erosion and deposition volume gradually decreases,which means that the riverbed erosion is approaching equilibrium.Additionally,we derive a formula for the spatial distribution of main channel accumulated erosion volume per unit river length in the LYR based on the non-equilibrium suspended sediment transport equation.The coefficient of determination between the fitted value and observed value from 2003 to 2015 is about 0.98-0.99,with a relative error of approximately 6.2%.Our findings suggest that under the current conditions of decreasing sediment inflow and continuous scouring,it takes around 3.0 years for the riverbed to achieve half of the erosion and deposition adjustment and approximately 13.0 years to achieve 95%of the adjustment.Moreover,the spatial distribution of accumulated erosion volume in the LYR tends to become more uniform with the continuous development of erosion.These results provide valuable reference for analyzing the complex spatio-temporal variation process of the LYR.