A new, unsteady analytical solution is presented to simulate the spatio-temporal variation in salinity in convergent, well-mixed estuaries. A first application in the Pearl River estuary shows it to be an efficient approach for predicting salt intrusion dynamics with satisfying accuracy. The model can be used to decide on water-fetching methods related to drinking-water supply. The model explains and quantifies the time difference between salinity at high water slack and the maximum salinity.

In this work, Van der Burgh's coefficient, K, is determined in the dry and wet seasons in a salt plug estuary to examine the contributions of tidal versus density-driven salt transport mechanisms. Gravitational circulation was entirely dominant over tidal dispersion in the wet season, whereas density-induced inverse and positive gravitational circulation facilitated an inverse and a positive estuarine circulation seaward and landward from the salt plug area during the dry season, respectively.