Abstract The spectrum of tidal and subtidal water level variations in river deltas responds to river discharge variation, ocean tides, and human activities of many kinds. It remains a contemporary challenge to identify the main sources of changes in tidal dynamics in deltas, because of nonlinear interactions between tides and the river discharge in a changing setting. Understanding the main forcing factors controlling the evolution of mean water levels and the associated amplitudes and phases of tidal constituents can help to understand the causes of floods and the occurrence of low flows hindering navigation. Here, a nonstationary harmonic analysis tool (NS_TIDE) is applied to hydrological data from 14 stations in the Pearl River Delta (PRD) spanning the period 1961–2012. The water levels and main tidal constituent properties are decomposed into contributions of external forcing by river discharges and ocean tides, providing insight into the nonstationary tidal-fluvial processes. Significant temporal trends in mean water levels and tidal properties are observed in the PRD. Results indicate that there is spatial variability in the response of mean water levels and tidal properties to river discharge variation in the delta. The abrupt changes in bathymetry in the delta due to intensive sand excavation are likely responsible for the observed spatial variations in tidal response, which reduce the flood-dominant tidal asymmetry in this area.

中文翻译：

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珠江三角洲河流流量和海潮趋势对水位动态的影响

摘要 河流三角洲的潮汐和潮下水位变化谱响应河流流量变化、海洋潮汐和多种人类活动。由于在不断变化的环境中潮汐和河流流量之间的非线性相互作用，确定三角洲潮汐动力学变化的主要来源仍然是当代的挑战。了解控制平均水位演变的主要强迫因素以及潮汐成分的相关幅度和相位有助于了解洪水的原因和阻碍航行的低流量的发生。在这里，非平稳谐波分析工具 (NS_TIDE) 应用于珠江三角洲 (PRD) 1961-2012 年期间 14 个站点的水文数据。水位和主要潮汐成分特性被分解为河流排放和海洋潮汐的外部强迫的贡献，提供对非平稳潮汐过程的深入了解。在珠三角观察到平均水位和潮汐特性的显着时间趋势。结果表明，平均水位和潮汐特性对三角洲河流流量变化的响应存在空间变异性。由于大量挖沙导致三角洲水深的突然变化可能是观察到的潮汐响应空间变化的原因，这减少了该地区以洪水为主的潮汐不对称性。在珠三角观察到平均水位和潮汐特性的显着时间趋势。结果表明，平均水位和潮汐特性对三角洲河流流量变化的响应存在空间变异性。由于大量挖沙导致三角洲水深的突然变化可能是观察到的潮汐响应空间变化的原因，这减少了该地区以洪水为主的潮汐不对称性。在珠三角观察到平均水位和潮汐特性的显着时间趋势。结果表明，平均水位和潮汐特性对三角洲河流流量变化的响应存在空间变异性。由于大量挖沙导致三角洲水深的突然变化可能是观察到的潮汐响应空间变化的原因，这减少了该地区以洪水为主的潮汐不对称性。