Delineation and Mapping of Groundwater Quality in Coastal Blocks of Tiruvallur District of Tamil Nadu Using GIS

An investigation was carried out to assess the quality of groundwater in coastal blocks of Tiruvallur district, Tamil Nadu. Approximately fifty groundwater samples were obtained from the coastline blocks in May 2022, particularly Minjur (25 Nos), Puzhal (7 Nos,) and Gummidipoondi (18 Nos). The groundwater samples were tested for physio-chemical (pH and EC) and chemical characteristics like cations-Ca2+, Mg2+, Na+, K+ and anions- CO32-, HCO3-, Cl-, and SO42- ; and the resultant properties were computed (SAR and RSC). The pH of Minjur, Puzhal, Gummidipoondi blocks ranged from 7.66 to 8.78, 7.77 to 8.36 and 7.35 to 8.76 respectively.The EC of Minjur ,Puzhal,Gummidipoondi were 0.3 to 3.56 dS m-1,0.76 to 2.91 dS m-1 and 0.2 to 2.07 dS m-1 respectively. The SAR of Minjur, Puzhal, and Gummidipoondi ranged from 1.60 to 11.73 ,1.67-10.01, 0.6 to 6.87 respectively. . The RSC of Minjur ,Puzhal, Gummidipoondi ranged from -4 to 8.4 meq l -1 ,-0.8 to 3.4 meq l -1, -4.4 to 4.8 meq l -1 respectively. In the Minjur block, the majority quality of groundwater was characterized as good quality water (32 per cent), salty water (24 per cent), and alkali water (36 per cent). While in the Puzhal block, the majority quality of groundwater was characterized as good quality water (28.57 per cent), saline water (14.28 per cent), and alkali water (57.14 per cent). In the Gummidipoondi block, the majority quality of groundwater was assessed as good quality water (38.8 percent), and alkali water (50 per cent).