Delineation and quantification of groundwater resources affected by seawater intrusion along the east coast of India

Overextraction of groundwater from coastal aquifers results in seawater intrusion causes immense threat to groundwater resources. The objectives of this study are to delineate the coastal regions affected by seawater intrusion along the east coast of India and to estimate the quantum of groundwater resources affected by seawater intrusion. The groundwater level, quality, and quantity data of groundwater along with its draft along the east coast for the year 2017 were collected from India WRIS. About 86% of groundwater pumped is used for irrigation and 14% of groundwater pumped is used for domestic and industrial purposes along the east coastal regions. The groundwater is being over exploited in Chennai, Nagapattinam, Puducherry, and Thanjavur districts of Tamil Nadu. The groundwater level is lower than mean sea level in most of the regions of Tamil Nadu, Andhra Pradesh, and Odisha where seawater intrusion is expected. The geochemical signatures such as Na/Cl and Cl/HCO 3 indicate that 35% of groundwater samples are affected by the seawater intrusion along the east coast. It is estimated that about 10,248 Mm 3 of groundwater resources in the east coast of India are affected due to seawater intrusion, among which some parts of Tamil Nadu and Andhra Pradesh are highly affected. Around seven districts in the east coast of India are very much affected by incursion of seawater as inferred from groundwater level and geochemical signatures. Hence, it is necessary to regulate groundwater pumping and also to augment groundwater storage by suitable managed aquifer recharge methods.