sustainability Article Spatial Characterization of Seawater Intrusion in a Coastal Aquifer of Northeast Liaodong Bay, China Jun Ma 1 , Zhifang Zhou 1,*, Qiaona Guo 1, Shumei Zhu 1, Yunfeng Dai 2 and Qi Shen 1 1 School of Earth Sciences and Engineering, Hohai University, No. 8 Focheng West Road, Nanjing 211100, China;
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[email protected] Received: 21 October 2019; Accepted: 3 December 2019; Published: 9 December 2019 Abstract: The safety of groundwater resources in coastal areas is related to the sustainable development of the national economy and society. Seawater intrusion is a serious problem threatening the groundwater environment in coastal areas. Climate change, tidal effects and groundwater exploitation may destroy the balance between salt water and fresh water in coastal aquifers, leading to seawater intrusion. The threat of seawater intrusion has attracted close attention, especially in the coastal areas of northern China, and the accuracy and efficiency of seawater intrusion monitoring need to be improved. The aim of this study was to fill the blanks in seawater intrusion research in the coastal aquifer of the Daqing River Catchment, northeastern Liaodong Bay, China, and determine the extent and evolutionary characteristics of seawater intrusion in this area. In this study, historical chloride concentration data were used to trace the evolution of the salinization, and electrical resistivity tomography (ERT) was used to supplement the data in areas with limited hydrochemical data and to detect the saltwater/freshwater interface, especially in the area near the Xihai Sluice.