Seawater Intrusion-Retreat Processes and Groundwater Evolution in Intruded Coastal Aquifers with Land Reclamation: A Case Study of Eastern Jiangsu, China

Abstract

The hydrogeochemical analysis and numerical simulation were conducted to explore the impact of land reclamation on submarine groundwater discharge and groundwater evolution in the seawater intrusion-retreat processes in eastern Jiangsu, China. The hydrogeochemical results indicated that the origin of salt in most groundwater is saltwater mixing, and weathering-dissolution of minerals enriches the salt in fresh groundwater. The evolution path of coastal groundwater in Jiangsu is Ca-Na-HCO3-Cl → Ca-Na-Cl-HCO3 → Na-Ca-Cl-HCO3 → Na-Mg-HCO3 → Na-Mg-HCO3-Cl → Na-Cl-HCO3 → Na-Cl, and the difference in groundwater evolution in different regions is obvious. The numerical simulation revealed that the land reclamation has blocked groundwater exchange and restrained the seawater intrusion. The sensitive analysis indicated that the permeability and the slope of the land reclamation have dominated the salinity distribution. And the aquifer heterogeneity promotes groundwater evolution and leads to the irregular salinity distribution of the groundwater. Moreover, the groundwater evolution in the shallow aquifer with the land reclamation shows that the residual seawater is gradually desalinating and discharged into the sea. The land reclamation is salinized by saltwater discharge and seawater intrusion together and then subsides into a stable saltwater wedge. The groundwater salinity distribution in Jiangsu is not fit seawater intrusion, which is caused by the coastline changes due to anthropogenic land reclamation and natural activities.

Effects of Land Reclamation on a Subterranean Estuary

“…While such a role of the low‐ K sr reclamation soil becomes weaker for large tidal amplitudes (e.g., A = 1.5 and 2.0 m), as the intrusion lengths are larger than those in the other two cases. Several studies have reported that land reclamation would mitigate seawater intrusion by moving the saltwater‐freshwater interface seaward (Abd‐Elhamid et al., 2020; Chen & Jiao, 2007; Xiong et al., 2022). However, the findings from Figure 6b indicate that seawater intrusion may not be necessarily alleviated by land reclamation, particularly when the reclamation soil is less permeable and the tidal amplitude is large.…”

“…However, in situations of large tidal amplitudes (e.g., A = 2.0 m), the seaward retreat of SW is more prominent in the aquifer reclaimed by more permeable soils. The comparison in Figure 6b demonstrates rather close seawater intrusion Chen & Jiao, 2007; Xiong et al, 2022). However, the findings from Figure 6b indicate that seawater intrusion may not be necessarily alleviated by land reclamation, particularly when the reclamation soil is less permeable and the tidal amplitude is large.…”

Analysis of the Seawater Intrusion Process Based on Multiple Monitoring Methods: Study in the Southern Coastal Plain of Laizhou Bay, China

“…The monitoring target of seawater intrusion is the change in the intrusion transition zone or interface, with indirect reflection factors including changes in vegetation cover, degree of soil salinity, etc., and direct reflection factors including the chemical characteristics of groundwater, groundwater table (or water head), etc. [21,22]. Monitoring methods mainly include the Water Chemical Sampling Analysis Method, Isotope Hydrogeochemical Method, Fixed-point Well Monitoring Method, and Geophysical Monitoring Method (Table 1) [23][24][25][26][27].…”