Comparison of indicators for the assessment of saltwater intrusion in coastal aquifers——taking aquifers in Pearl River Estuary as an example

Saltwater intrusion (SWI) represents a threat to coastal aquifers worldwide by rendering groundwater quality not viable for its intended purposes.Therefore, understanding and assessing the impact of SWI effectively is indispensable for the aquifer management and the health of residents.Nowadays, SWI assessment from hydrogeochemical aspect generally includes single factor and multiple indexes.In the study, taking aquifers in Pearl River Estuary as an example, the paper comprehensively expounds the hydrochemical indicators and their principles including the methods which are seldom used in China.Then the effectiveness, time consumed and economic cost of the variable indicators are compared and the associated practical problems are evaluated.The results indicate that Cl^- and TDS indicators are simple ways that could be used as effective direct single factors in the SWI evaluation, especially for large-scale.Meanwhile, the Ca²⁺ related indicators are not sensitive to separate the freshwater and saltwater in the study domain.Among the complex factors, SAR, BEX and GQI_SWI are highly correlated with Cl^- and could illustrate the ion exchange in the SWI process.The research provides a comprehensive review of most of the indicators which commonly used in assessing the dynamics of SWI and compares their potential impacts.The paper as well as provides an effective way for informed impact assessment and planning for sustainable exploitation of coastal aquifers.