Past, present, and future of global seawater intrusion research: A bibliometric analysis

Abstract Seawater intrusion (SWI) is becoming one of the major environmental issues in more and more coastal areas around the world. Understanding the current SWI situation and forming research consensus are of great significance for further studies and coastal water resources management. In this study, we analyzed the SWI-associated literature available from the Science of Citation Index Expanded (SCIE) bibliographic database by using CiteSpace to further excavate existing research achievement. We explored a new method for identifying global geographic distributions of 501 coastal cities where SWI has been reported. It can be found that SWI is more likely to occur in well-recharged major basins (recharge rate 100–300 mm/a) or local shallow aquifers with high population density. According to current reports, about 32% of the coastal metropolitan cities (population > 1 million within 150 km from coastline) have been threatened. There was a 20-fold increase rate in the number of papers related to SWI compared to that in general science and technology. The United States of America, China, Australia were the top 3 contributors in SWI scope, contributed 46.4% of the total number of articles. More than 600 researches were supported by Chinese funds, which made China become the second contributor. But the number of citations per Chinese article was the lowest among the top 10 contributors. By co-citation analysis, we identified top 5% articles, and elaborated the background knowledge by taking Top 10 co-cited articles as example. A series of keywords with high co-occurrence were identified. Their meanings and relations were stated and graphically illustrated. As a keyword, SWI frequently appears in the following five research directions: analysis of the location or morphology of fresh and salt water interface, the prediction of groundwater quality, the geothermal circulation and tectonic activities, the coastal mangrove wetlands protection, and the management of water resources in coastal zones. We critically evaluated the bibliometric results and reviewed future opportunities and challenges for this field. With the development of new technology and the accumulation, the improvement of coastal environment will certainly benefit from the study of SWI.