Characterizing groundwater quality and seawater intrusion in coastal aquifers of Nagapattinam and Karaikal, South India using hydrogeochemistry and modeling techniques

A severe problem of water supply in eastern coastal India is the saline water intrusion into aquifers due to growing industrialization, urbanization, groundwater withdrawals and sea-level rise. The present study investigated the groundwater quality and sea intrusion in a coastal area of southern India using different techniques. A total of 122 groundwater samples were collected during May 2014 representing summer (SUM) and August 2014 representing southwest monsoon (SWM), and analyzed for 12 chemical parameters (Na+, K+, Ca2+, Mg2+, Cl-, SO42-, HCO3-, NO3-, F- PO4-, Si and TDS). Water quality index (WQI) was used to determine the groundwater quality. The WQI suggests that more samples during SWM are classified as poor quality than in SUM due to multiple factors seawater intrusion, ion exchange, excess withdrawal, sewages impact and agricultural activity. The spatial of Cl-, EC and WQI indicate that Cl- and EC related to poor quality groundwater. Saline water mixing index indicates greater percentage (35%) of samples during SWM, influenced by seawater intrusion noted toward western and eastern localities of the study area. The SEAWAT model attempted describes seawater intrusion noted along the eastern stretches of the study area owing to excess withdrawal and simulation for 50 years suggests further migration inland.