Delineation of groundwater potential zones along the coastal parts of Kanyakumari district, Tamilnadu

Electrical resistivity method is widely used in groundwater exploration studies because it is a fast and less expensive geophysical tool. The vertical electrical soundings were carried out at 21 sites along the coast of Agastheeswaram taluk between Muttom and Vattakkotai, Kanyakumari district, Tamil Nadu using the Schlumberger configuration. The field data were interpreted using the IPI2win software and the resistivity versus depth models for each location was prepared. Groundwater in this region occurs mainly under semi confined to confined conditions. The study was aimed at improving the success rate of boreholes. The results obtained from the interpreted data indicate three to four geoelectric layers. The thickness of the first and second layers lies between 1 to 4.7m and 1.1 to 13.3m respectively. The sounding locations showing resistivities between 18-100 ohm m are expected to be potential zones with potable water as revealed by TDS value of groundwater from the nearby wells. The areas affected by over exploitation and saline water intrusion into groundwater are also delineated by very low resistivity zones (between 1and 9.6 ohm m). The geoelectric sections prepared on the basis of VES results clearly delineated the fresh and saline water zones both laterally and vertically. The saline water intrusion can be reduced significantly by construction of barriers to prevent the intrusion of saline water from the nearby estuaries and salt pans. It is also necessary to construct structures to increase the groundwater level through artificial recharge. The saline water intrusion can also be reduced by adopting a suitable pumping pattern. Thus, these studies supported by available litholog data helped in suggesting suitable management techniques to prevent the groundwater degradation.