Mitigation of Seawater Intrusion by Managed Aquifer Recharge through Check Dams in Coastal Aquifers north of Chennai, India

The objective of the study is to assess the effect of a check dam across a non-perennial river in enhancing groundwater storage and mitigating seawater intrusion in the region north of Chennai, India. Water level in a check dam constructed as a measure of managed aquifer recharge and in the wells located around it was measured once a month from July 2010 to July 2012. Water samples from the dam and wells were also collected and analysed for electrical conductance and major ions once a month. The groundwater table has increased by 1.5 m after the construction of the check dam. The geochemical signatures of the groundwater samples from the wells located within 1.5 km from the check dam were more or less similar to that of the water in the dam. The check dams across Arani and Koratallai rivers has resulted in harvesting about 9% and 11% of runoff respectively. Raise in water table due to the storage in the check dams is expected to push the seawater-freshwater interface by about 2 km towards the sea in future. The check dams in this region have improved the groundwater quantity and quality with very minimal changes in the hydrological balance.