Accurate salinity prediction can support the decision-making of water resources management to mitigate the threat of insufficient freshwater supply in densely populated estuaries. Statistical methods are low-cost and less time-consuming compared with numerical models and physical models for predicting estuarine salinity variations. This study proposed an alternative statistical model that can more accurately predict the salinity series in estuaries. The model incorporates an autoregressive model to characterize the memory effect of salinity and includes the changes of salinity driven by river discharge and tides. Furthermore, the Gamma distribution function was introduced to correct the hysteresis effects of river discharge, tides and salinity. Based on fixed corrections of long-term effects, dynamic corrections of short-term effects were added to weaken the hysteresis effects. Real-world model application to the Pearl River Estuary obtained satisfactory agreement between predicted and measured salinity peaks, indicating the accuracy of salinity forecast. Cross-validation and weekly salinity prediction under small, medium and large river discharges were also conducted to further test the reliability of the model. The statistical model provides a good reference for predicting salinity variations in estuaries.

In recent years, hydrogeologists have paid more and more attention to the discharge of submarine groundwater(SGD), which is a typical and important process of the interaction between seawater and groundwater in coastal areas, tidal flats and estuaries. As an important sources of water and chemical materials to ocean, SGD affects the global water cycle and coastal ecological environment. SGD also influence the transport path of pollutants from land to the sea. Therefore, it affects the local and global circulation of coastal groundwater and seawater. Since it usually occurs in aquifer, it is easily overlooked by the researchers. In addition, due to the uncertainty of SGD in time and space, it is difficult to be measured accurately. Aiming at recently study, this paper will discuss the research process, research method, research field and environmental significance of SGD on the coast of the Huanghai and the Bohai. Based on the analysis of the existing research results, some suggestions on improving SGD investigation are put forward.