Cognizance about sea water intrusion by chemical analysis in coastal aquifer of southeast coast of India

Water is an unavoidable natural resource on this planet that can be used for a variety of purposes, including drinking, domestic, agricultural, and industrial activities. Throughout the world, the human population is high along the coastal regions where groundwater acts as a major source for all their needs. The excess withdrawal of groundwater to serve such a huge population in coastal aquifers led to seawater intrusion. This research work focuses on tracing the signature of seawater ingress into the coastal aquifers of the southeast coast of the Puducherry region lying along the southwest coast of the Bay of Bengal. To study the effect of seawater intrusion in coastal aquifers, 48 groundwater samples were collected in three seasons, namely, Pre-Monsoon (PRM, N = 16), Monsoon (MON, N = 16), and Post-Monsoon (POM, N = 16). The collected water samples were analyzed for hydrochemical parameters such as pH, Electrical Conductivity (EC), Total Dissolved Solids (TDS), Sodium (Na + ), Potassium (K + ), Calcium (Ca 2+ ), Magnesium (Mg 2+ ), Chloride (Cl − ), Sulphate (SO 4 2− ), Bicarbonate (HCO − 3 ), Total Hardness (TH), and Total Alkalinity (TA). According to the analysis, it is found that Na + and Cl − are the dominant cation and anion in groundwater samples of the study area, respectively. The mixing of seawater with freshwater in the study area was evaluated using the Piper diagram, Chadha’s plot, and groundwater quality index for seawater intrusion (GQI Sea ). Based on the ratio of Na + /Cl − , it is found that 25%, 13%, and 19% of samples in PRM, MON, and POM show a strong signature of seawater ingress. The plot of Simpson’s ratio vs. distance shows that the groundwater of the study area has been affected by seawater intrusion for about 3 km from the sea shore.