Salt Intrusion as a Function of Estuary Length in Periodically Weakly Stratified Estuaries

Abstract

Salt water can intrude rivers through estuaries and affect freshwater intake for domestic, agricultural, and industrial uses in surrounding lands. Estuarine salt intrusion also creates horizontal and vertical density gradients, which drive a residual current (i.e., gravitational circulation, GC) and determine density stratification. Hence, salt intrusion modifies the fate and transport path of other waterborne materials (e.g., sediment, nutrients, pollutants) and strongly affects the healthy functioning of estuarine ecosystems.In recent decades, due to human activities (e.g., increasing upstream freshwater abstraction, channel deepening, sand mining) and climate change (e.g., extreme droughts, sea level rise), salt intrusion has been increasing in estuaries worldwide. Examples are the Pearl River and Yangtze estuaries,

Salinity Distribution in a Tropical River-Estuary Continuum through Numerical Modelling: Case of the Wouri-Nkam River Estuary, Cameroon

“…Similar findings have been obtained by many authors in different estuaries (Brockway et al 2006;Savenije 2009;Shaha and Cho 2009;Zhang et al 2010;Wei et al 2022).…”

“…In shallow water systems, any increase in the salinity of the water table may cause a corresponding increase in the saltwater infiltration in the soil through capillary rise (Prathapar et al 1992;Werner and Lockington 2004). Globally, climate change (extreme droughts and sea level rise) and anthropic activities (channel deepening, sand mining and freshwater extraction for domestic and/or agricultural use) may cause salinity incursions further upstream (Chen et al 2016;Wei et al 2022). For these reasons, it is important for water resources managers to know and regulate the minimum volume of river discharges into the estuary to prevent salt intrusion and sustain freshwater availability for domestic and industrial uses (Qiu and Zhu 2013).…”

“…By so doing, they will provide the primary estimates of saline intrusion strength and range before making any scientific, political or management decisions (Haddout et al 2016). In recent decades, salinity barriers were built to alleviate the hostile impact of saline water intrusion in estuaries, thus protecting the freshwater and maintaining the estuarine ecosystem in a healthy state (Wei et al 2022). However, these barriers need to be prudently planned for the reason that they are expensive and may have negative impacts on the migration of fish species (Harris et al 2016) and the sediment transport (Ridderinkhof et al 2014).…”

Assessment of changes in severity of compound drought and saltwater intrusion events based on a multi‐index approach in Pearl River estuary

“…Previous studies have shown that hydrological drought and saltwater intrusion in coastal areas are usually interdependent and that human activities, such as irrigation in coastal areas, reservoir regulation, and water transfer projects, directly influence the evolution of hydrological drought by altering the hydrological processes in the basin, which in turn may affect the evolution of compound drought‐saltwater intrusion (Wu et al, 2022). In this study, we focus only on runoff (SRI) and saltwater intrusion (SSI) because hydrological drought and saltwater intrusion are closely related to water supply in estuary (He et al, 2022; Wei et al, 2022). To address this limitation, more factors (e.g., precipitation, temperature, wind, tide, runoff and saltwater) should be included to complement the framework in future studies.…”

Fortnightly variability of horizontal salinity gradient affects exchange flow in the Sumjin River estuary

“…However, as these studies were conducted only at specific points, the fortnightly variation of exchange flow over the whole short estuary remains unclear. In the study of the short Blackwater estuary, a semi-analytical approach was used and the analysis focused on lateral changes in residual circulation, but did not examine spring-neap variation (Wei et al, 2022). Therefore, fortnightly variation of the vertical shear of exchange flow in the entire estuary is still poorly understood as the analysis has received little attention.…”