Effects of Typhoon on Saltwater Intrusion in a High Discharge Estuary

Abstract

Basic models of salinity intrusion (e.g., Monismith et al., 2002) suggest that the steady state intrusion length depends on the river discharge and the downgradient salt flux caused by estuarine circulation and tides. However, subsequent studies (Aristizabal & Chant, 2013;Ralston et al., 2008) have highlighted that complex bathymetry also plays a significant role in determining saltwater intrusion length and rarely are estuaries in steady state (Lerczak et al., 2006). In addition to river discharge and tides, along-channel (i.e., axial) wind stress also influences saltwater intrusion, stratification, and exchange flow (Chen & Sanford, 2009;Geyer, 1997;Hansen & Rattray, 1965;Scully et al., 2005). Yet, the response of the estuarine salt field to cyclone-scale winds and different river discharges remains scarcely studied. Here, we employ a numerical model to examine how the passage of typhoon Kong-rey (2018) caused a strong saltwater intrusion event in the Changjiang, as well as the underlying dynamics of the intrusion. In the following sections, we discuss the mechanisms that control saltwater intrusion in estuaries, especially under strong winds. Next, we introduce the saltwater intrusion case in the Changjiang Estuary. Mechanisms of Saltwater IntrusionIn estuaries, the interaction between river discharge and tides results in a longitudinal density gradient that drives the exchange flow. Through a steady balance between pressure gradient and frictional forces, Hansen

Impacts of Extratropical Cyclone Fiona on a sensitive coastal lagoon ecosystem

“…For example, elevated freshwater discharge to transitional coastal waters can decrease salinity, deplete dissolved oxygen (DO), dilute or enhance nutrient levels, increase suspended sediment and organic matter, and mix formerly stratified zones (Steichen et al 2020; González‐De Zayas et al 2021; Walker et al 2021). On the marine side, seawater intrusion can be triggered during coastal storms due to storm surges, landward Ekman transport, and wind‐sheared salt flux (Li et al 2022). The intruded seawater increases the salinity and alters coastal water temperatures through heat advection (Kurylyk et al 2023).…”

Satellite-Derived Indicators of Drought Severity and Water Storage in Estuarine Reservoirs: A Case Study of Qingcaosha Reservoir, China

“…Estuarine reservoir storage might be unstable due to continuous saltwater intrusion occurring during the dry season, when the river discharge is low or the oceanic dynamic condition is anomalously strong [10][11][12]. However, saltwater intrusions also occur, even during flood seasons under the influences of abnormally extreme drought [13,14] and typhoons [15,16]. For instance, 2022 was reported as a year of drought [17], when continuous drought occurred in the Changjiang River Basin.…”