Role of GIS in deciphering hydrogeochemical processes and quality in Pudukottai district, Tamil Nadu, India

This study addressed hydrogeochemical characterization and groundwater quality degradation for drinking and irrigation purposes in Pudukottai district using a geographic information system. Eighty-seven groundwater samples were collected from the bore and dug wells during the pre and post-monsoon season in 2019. The order of mean ionic abundance is as follows Cl⁻ > HCO₃⁻ > Na⁺ > SO₄²⁻ > Mg²⁺ > Ca²⁺ > K⁺ (325.5 > 182.2 > 181.4 > 83.2 > 51.1 > 35.8 > 9.1 > 8.6 > 0.9 > 0.3) and Cl⁻ > Na⁺ > HCO₃⁻ > SO₄²⁻ > Mg²⁺ > Ca²⁺ > K⁺ (415.7 > 230.3 > 198.2 > 82.9 > 53.8 > 43.4 > 14.9) in both seasons. Analytical results are presented in Piper, Gibbs, Na% vs. EC, USSL and PI plots used to evaluate the hydrogeochemical processes. The interaction between rock water and evaporation processes leads to variations in the hydrogeochemistry of the study area during pre and post monsoon. Almost 15% of the groundwater samples were not suitable for drinking according to the standard, which is common in the south-eastern region of the study area. From the results of Na%, SAR, RSC, MgC and KR, majority of the groundwater samples were suitable for irrigation purpose. The higher concentrations of EC, TDS, Cl⁻ and Na⁺ values were found in the southern region, which is due to seawater intrusion caused by excessive pumping in the coastal regions. Drinking water quality index (DWQI) and irrigation water quality index (IRWQI) are calculated to determine the suitability of groundwater for drinking and irrigation purposes. Scatter plots show that the dissolution of carbonate minerals by the reverse ion exchange process increases the ions content of groundwater. In addition, statistical analysis of correlation matrix, PCA and cluster analysis were carried out to understand the relationship between the parameters and factors affecting hydrogeochemistry. However, the study concludes that most of the district is suitable for both drinking and agricultural purposes and can be used for sustainable growth. It is also recommended that, artificial recharge structures be introduced to improve groundwater quality in this region.