Abstract
Abstract. Knowledge of the processes governing salt intrusion in estuaries is important, since it influences the eco-environment 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 water-fetching methods to make good use of water resources.
Highlights
Salt intrusion in a river connecting to the sea is largely controlled by the river flow (Keulegan, 1966)
It is noticed that the maximum salinity appears after high water slack (HWS) and the minimum salinity appears before low water slack (LWS)
The time lag between salinity extremes and slack water is determined by the strength of the river flow in a way that is consistent with the previous observations in which the maximum salinity appears after HWS and the minimum salinity appears before LWS
Summary
Salt intrusion in a river connecting to the sea is largely controlled by the river flow (Keulegan, 1966). The natural variability in river and tidal inputs to estuaries has been greatly disrupted as a result of the impact of global climate change and sea level rise as well as of local human activities, such as dam construction and channel dredging These changes cause salt intrusion to become a serious problem in estuaries. It influences water quality, agricultural development in lowland areas, water utilization in upstream catchments, and the aquatic environment in estuaries (Han et al, 2010; Mo et al, 2007; Savenije, 1992).
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