Many estuaries worldwide are subject to significant human interventions, such as dam construction, channel deepening, and land reclamation. However, the impact of these interventions on the spatiotemporal river-tide dynamics is insufficiently understood. In this study, we explored the seasonal changes in river-tide dynamics in the Modaomen Estuary of the Pearl River, where a significant increase in tidal range by approximately 0.14 m on average was observed after substantive channel deepening mainly due to human-induced sand excavations. Using the double mass curve approach with regard to the river discharge and the absolute value of tidal damping rate (or residual water level slope), we identified three stepwise phases (i.e. 1960–1990 representing the pre-human intervention period, 1991–2000 representing the transitional period, and 2001–2016 representing the post-human intervention period) corresponding to high to low residual water level slopes, and qualitatively matched the river-tide dynamics shift observed in the Modaomen Estuary. It was shown that the increase in tidal range was primarily due to the reduction in residual water level slope (and thus the weakening of the tidal damping effect) caused by the channel deepening along the Modaomen Estuary (with length of 124 km) where the residual water level slope was decreased by 46% from the pre-human period (1960–1990) to the post-human period (2001–2016), while the absolute value of the tidal damping rate was decreased by 32% due to the overall impacts from human interventions. Based on the regression coefficients obtained from the double mass curve approach, we showed that the river-tide dynamics in terms of tidal damping rate and residual water level slope were more sensitive to human interventions during the dry season than during the wet season, owing to the combined impacts of riverbed deepening and freshwater regulation by dam's operation. The underlying mechanism could be primarily attributed to the considerable seasonal variation in the lateral storage area (such as tidal flats or salt marshes). The results also showed that larger freshwater discharge is required to alter the critical value of maximum tidal damping (indicating the strongest damping effect along the channel) owing to the increase in tidal range due to substantial riverbed deepening and hence significant increase in channel storage. The method proposed in this study to quantify the overall impacts of human interventions on seasonal changes in river-tide dynamics is particularly useful for setting scientific guidelines for sustainable water management and conservation planning for engineering works in the Modaomen Estuary and other estuaries with significant human interventions.

全球许多河口都受到人类的重大干预，例如大坝建设，河道加深和土地开垦。但是，这些干预措施对时空河潮动态的影响尚不充分了解。在这项研究中，我们探索了珠江磨刀门河口河潮动态的季节变化，在该河道中，由于人为引起的砂土开挖，实质性通道加深后，潮汐范围平均平均增加了约0.14 m。 。使用关于河流流量和潮汐阻尼率（或剩余水位坡度）的绝对值的双重质量曲线方法，我们确定了三个阶段性阶段（即1960–1990代表人类干预之前的时期，1991–2000代表人类干预时期）过渡时期 （2001-2016年代表人类干预后的时期），对应于高到低的剩余水位斜率，并且定性地匹配了在墨刀门河口观察到的河潮动态变化。结果表明，潮汐范围的增加主要是由于沿莫道门河口（长度为124 km）的河道加深造成的残余水位斜率减小（因而减弱了潮汐阻尼作用）。从人类前期（1960–1990）到人类后期（2001–2016），水位斜率降低了46％，而潮汐阻尼率的绝对值由于总体影响而降低了32％来自人为干预。根据从双重质量曲线法获得的回归系数，我们发现，由于大坝运行对河床加深和淡水调节的综合影响，在干季期间，潮汐动力对潮汐阻尼率和剩余水位坡度的影响比干季对人类干预更为敏感。潜在的机制可能主要归因于侧向存储区域（例如，潮滩或盐沼）中相当大的季节性变化。结果还表明，由于大量河床加深导致潮汐范围增加，因此需要更大的淡水排放量来改变最大潮汐阻尼的临界值（表明沿河道的最强阻尼作用）。