A hydrogeochemical appraisal and multivariate statistical analysis of seawater intrusion in point calimere wetland, lower Cauvery region, India

Seawater intrusion is a major threat to the water quality in the coastal aquifers. A hydrogeochemical survey was conducted in and around the Point Calimere wetland with an objective to delineating the impact and sources of groundwater salinization. These objectives were met by a combined hydrochemical and multivariate statistical approach. Groundwater samples showed an alkaline nature throughout the area. It was substantiated by the observed positive correlation of TDS with Na, Mg and Cl and a negative correlation with HCO3. Ionic changes during the saline water-freshwater mixing were analyzed. It was detected that the mixing rate of seawater with the fresh groundwater was 31%. A negative e.(change) was observed for the samples collected near the coast as well as salt pans. The sources of salinity identified through factor analysis exhibited a clear segregation between freshwater and saline water. The presence of Ca and SO4 in the factor 2 shows the dissolution of gypsum minerals. The dendrogram generated through cluster analysis classified the total groundwater samples into two groups which agrees with the results obtained from the hydrochemical and factor analysis. The wells that are near the coast and salt pans, which are grouped under cluster 1, have influence of saline intrusion.