Assessment of groundwater quality in Kanyakumari district, Tamil Nadu, using ionic chemistry

Saline or alkali water also constitutes an important source of irrigation for agricultural production. A study was undertaken at the block level to evaluate major ion chemistry and suitability of water for irrigation purpose in Kanyakumari district, Tamil Nadu, India. A total of 215 groundwater samples were collected and analysed for major ions and the analytical data were interpreted according to established guidelines. The spatial map shows that calcium (Ca²⁺) is the most dominant cation with bicarbonate (HCO) and chloride (Cl−) as the dominant anions. The abundance of cations follows the order Ca > Mg > Na > K and that of anions HCO₃ > Cl > SO₄. The distribution of water samples in different water quality classes based on pH, EC, residual sodium carbonate and sodium adsorption ratio reveals good-quality underground irrigation water in most of the blocks, except Tholavai. In Thucklay, 100% of the groundwater can be used, whereas 89.7% can be used in Rajakamangalam, 81.25% in Munchirai, 80.95% in Thiruvattar and 73.7% in Kuruthencode. The Thovalai block had saline water (73.68%) and marginally saline water (26.32%). Saline water was found in about 25% of the area in the district and in situ rainwater conservation for leaching of salts accumulated through saline water irrigation is an important technology. Thus, farmers need to be trained regarding these aspects. Such areas require adequate drainage and also introduction of salt-tolerant crops.