Interannual tidal range trend in Pearl River Delta

This paper analyzes the interannual tidal range trends and the abrupt change points of the 17 main hydrological stations in the Pearl River Delta since 1950s.Autocorrelation has been removed from the original sample using the Trend Free Pre-Whitening procedure before the non-parametric method Mann-Kendall test is applied.The results indicate that there is spatial variability of the annual tidal range in the Pearl River Delta.In the middle and upper reaches,the tidal ranges display significant increasing trend.The upper reach it goes,the more obvious the increasing trend is.While near the estuary,most stations show significant decreasing trend in the tidal range due to intensive human activities,such as land reclamations.The result of the Pettitt test indicates that the abrupt changes of most stations occurred in the 1980s,which is accordance with the period of large-scale sand excavation occurrences in the delta.This implies that sand excavation is the main factor leading to the tidal range variability.The increasing trend in the tidal range also indicates the increase of the tidal dynamics in the delta,which is also one of the reasons for the saline intrusion problem happening in the recent years.