珠江三角洲河网地形和径流条件变化对潮动力格局的影响

Effects of changes in river network topography and runoff on tidal dynamic pattern in Pearl River Delta

针对上游建库及航道疏浚等人类干预引发的河床不均匀下切与径流年内分配调整导致珠江三角洲河网内径流、潮汐、河口地形间相互作用随之变化的问题,基于连续小波变换方法,结合实测水文资料与河网一维水动力模型,对比分析了地形与径流变化前后河网潮动力格局的调整,并将一维圣维南方程中的非线性摩擦项分解为径流成分、径潮作用成分、潮汐成分,量化了各成分对于潮动力格局调整的贡献。结果表明:地形与径流变化后,洪季各潮族动力均显著增强,枯季高频潮族动力衰减更迅速,枯季径流量增加对潮汐的调制作用在大部分河道抵消了地形下切造成的潮汐动力增强;河网上游非线性摩擦项中径潮作用成分对于潮动力格局调整的贡献增大,径潮非线性作用增强。

The uneven undercutting of the riverbed and the adjustment of the intra-annual runoff distribution caused by human interventions,including upstream reservoir construction and channel dredging,have led to changes in the interactions between runoff,tide,and estuarine topography in the Pearl River Delta river network.Based on the continuous wavelet transform method,measured hydrological data and the one-dimensional hydrodynamic model of the river network were applied to comparatively analyzing the adjustment of tidal dynamic pattern in the river network before and after the changes in topography and runoff,and the nonlinear friction term in the one-dimensional Saint-Venant equation was decomposed into runoff component,runoff-tidal component,and tidal component to further quantify the contribution of each component to the adjustment of tidal dynamic pattern.The results show that,with the changes in runoff and topography,the tidal dynamics of different tidal species significantly increases in the flood season,the tidal dynamics of high-frequency tidal species decays more rapidly in the dry season,and the tidal modulation effect caused by runoff increase in the dry season offsets the tidal dynamic enhancement caused by topographic downcutting in most river channels;the contribution of the runoff-tide interaction component in the nonlinear friction term to the adjustment of tidal dynamic pattern in the upstream river network increases with the changes in runoff and topography,and the runoff-tide nonlinear action is enhanced.