Characteristics and Influencing Factors of Storm Surge-Induced Salinity Augmentation in the Pearl River Estuary, South China

Abstract

The Pearl River Estuary (PRE) frequently experiences the impacts of typhoons, storm surges, and saltwater intrusion. While previous research has mainly focused on saltwater intrusion during the dry season, there is limited research on saltwater intrusion caused by storm surges in the PRE. In this study, we systematically investigate the effects of ten typical autumnal typhoons and associated storm surges on saltwater intrusion in the Modaomen Waterway using in situ data of water level, river discharge, and chloride concentrations from 2006 to 2022. We introduce the concept of Storm surge-Induced Salinity Augmentation (SISA) and analyze its characteristics and primary influencing factors. Our findings reveal that SISA primarily occurs in autumn, with reduced upstream river discharge and the dominance of high-salinity water in the estuary. SISA occurs immediately after storm surges and grows rapidly and violently, with a time lag of 2–4 h, but rapidly recedes after the typhoon passage due to heavy rainfall and high freshwater discharge. Typhoons with a westward trajectory have a greater influence, and the southeastern winds outside the estuary during typhoon events are the primary factors determining the intensity of SISA. Pre-typhoon river discharge affects the range and duration of saltwater intrusion. Moreover, the coupling effect of extreme river dryness, spring tide, and storm surges significantly enhances saltwater intrusion. Further research is needed to quantify the spatiotemporal characteristics of SISA accurately.