Decadal variability of tidal dynamics in the Pearl River Delta: Spatial patterns, causes, and implications for estuarine water management

Abstract

AbstractIn this study, we examine the decadal variability of tidal dynamics in terms of the tidal range in the Pearl River Delta (PRD) from the 1950s to 2016. The Mann–Kendall trend test and Empirical Orthogonal Function (EOF) method are employed to identify the long‐term trends and spatial patterns of the annual tidal range series observed at 26 stations over the whole PRD, respectively. The results show that most stations display an increasing tidal range trend, except for some stations near estuarine outlets, which corresponds to the 1st EOF mode characterized by a rapid increase of the tidal range since the 1990s. This means that the cumulative impacts of human interventions reached their peak in the 1990s, exceeding the threshold of tidal dynamics in the PRD. To quantify human‐induced alternations of the tidal range, the tidal regime shift was subsequently explored by comparing the tidal ranges of the pre‐ and post‐1992 periods reconstructed from the EOF decomposition. The mechanism causing the tidal regime shift in the PRD can be attributed to the substantially reduced residual water level slope (hence, the effective bottom friction) that greatly enhances the tidal dynamics. Our study describes the shift of spatial–temporal tidal dynamics patterns in detail, which is particularly useful to guide effective and sustainable water management in the PRD and other river deltas that are subjected to intensive human interventions.