Analytical model captures intratidal variation in salinity in a convergent, well-mixed estuary

Abstract

Knowledge of the processes governing salt intrusion in estuaries is important, since it influences the ecoenvironment of estuaries as well as its water resource potential in many ways. Analytical models of salinity variation offer a simple and efficient method for studying salt intrusion in estuaries. In this paper, an unsteady analytical solution is presented to predict the spatio-temporal variation in salinity in convergent estuaries. It is derived from a one-dimensional advection-diffusion equation for salinity, adopting a constant mixing coefficient and a single-frequency tidal wave, which can directly reflect the influence of the tidal motion and the interaction between the tide and runoff. The deduced analytical solution is illustrated with an application to the Humen estuary of the Pearl River Delta (PRD) and proves to be an efficient and accurate approach for predicting the salt intrusion in convergent estuaries. The unsteady analytical solution is tested against observations from six study sites to validate its capability to predict intratidal variation in salt intrusion. The results show that the proposed unsteady analytical solution can be successfully used to reproduce the spatial distribution and temporal processes governing salinity dynamics in convergent, well-mixed estuaries. The proposed method provides a quick and convenient approach for deciding on waterfetching methods to make good use of water resources.

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

“…On the other hand, the presence of mangroves forests may have caused the overestimation of salinity during TA and HWS conditions; the mangroves trees (especially the Rhizophora species) may regulate the salinity content by absorbing salt water in their roots, leaves and propagules (Kiwoong et al 2016). Other authors when predicting salinity intrusion in ungauged estuaries in Malaysia and Hum estuary (Gisen 2015;Xu et al 2019) reached similar conclusions.…”

Assessing the Influence of Typhoons on Salt Intrusion in the Modaomen Estuary within the Pearl River Delta, China

“…Salt intrusion is influenced by various external factors, including river discharge, tides, and winds [6][7][8]. Of these, river discharge and tides have been extensively studied, as fundamental model outcomes indicate that the extent of steady-state intrusion is primarily reliant on these factors [9][10][11]. However, recent decades have witnessed a growing emphasis on the impact of wind on salt intrusion [12][13][14].…”

A Statistics‐Based Analytical Framework for Intratidal and Tidally Averaged Salinity Distribution in Estuaries

“…As salinity distribution curves along estuaries change with time, dynamics‐based models are best suited for diagnostic or prognostic purposes. Other efforts have been carried out to explore intratidal salinity distributions through analytical methods (i.e., simplified approaches) by using Fourier series expansions (Xu et al., 2019), and eigenfunction expansions (Dijkstra et al., 2022). However, these approximations disregard the salinity transport asymmetry (or mixing) within a tidal cycle, and at subtidal scales.…”