Assessment of groundwater vulnerability to seawater intrusion using multiple approaches

Saltwater intrusion is the critical concern commonly confronted in coastal aquifers around the world. This study assessed the principal physicochemical parameters influencing groundwater quality in the coastal areas of Visakhapatnam City by investigating the potential origins of seawater intrusion. First is an integrated approach wherein a primary survey was conducted to establish the quality and quantity of groundwater in the coastal areas of Visakhapatnam City. The groundwater vulnerability to seawater intrusion was analysed using four different methods. This study evaluated ionic molar ratios using multivariate statistical techniques, including hierarchical cluster analysis (HCA) and principal component analysis (PCA), GALDIT model. Hydrochemical evolution diagrams further support the analysis to assess the extent of seawater intrusion in the study area. Ionic ratios suggest that there are early signs of seawater intrusion into groundwater. From PCA, PC 1, the salinisation factor was evaluated for each season based on the variance percentage. Hierarchical cluster analysis grouped the 20 groundwater quality parameters into two key clusters. In the second cluster, the TDS and EC were the dominant parameters in all the seasons. The GALDIT model showed that about 10 (i.e. 33.33%) in pre-monsoon and 7 (i.e. 23.3%) out of 30 sampling stations fell under moderately vulnerable seawater intrusion while the rest fall under low-risk zones. The study with hydrochemical evolution diagrams indicates that Chepaluppada, Mangamaripeta and Jalaripeta in the pre-monsoon and Chepalappada, Timmapuram and Beach Road in the post-monsoon seasons are prone for seawater intrusion.