Hydrochemical characterization and groundwater quality in Cauvery deltaic fluvial plains of Southern India

Groundwater sources are drastically changing in their quantity and quality depending on local and regional level natural and anthropogenic factors, influencing their suitability for drinking and irrigation purposes. The objective of this study is to characterize the hydrochemistry and assess the groundwater quality in the fluvial deltaic plains of Cauvery river basin, Tamil Nadu, India. A total of 50 georeferenced groundwater samples were collected across Needamangalam block of Thiruvarur district and analyzed for major ions and hydrochemical processes. The results showed an ionic sequence of Cl− > Na+ > HCO3− > Mg2+ > Ca2+ > CO32− > SO42− > K+ based on their relative proportions. The scatter diagram indicated that groundwater chemistry was mostly influenced by weathering dominance followed by evaporation and silicate weathering. The dominant hydro-chemical facies were Na+-Cl−-HCO3− type, Na+-Mg2+-Cl−-HCO3− type, Na+-Cl−-HCO3−-CO32− type and Na+-Mg2+-Cl−-HCO3−-CO32− type influenced by the ion-exchange reaction. Most of the groundwater samples are suitable for drinking and irrigation except few with higher Na+ and Cl− content caused by the mixing of salt from fluvio-marine sources or agriculture return flow. The high sodium content in irrigation water may affect the soil hydraulic and nutrient properties in the long run.