Abstract
Seawater intrusion and degradation of fresh water into saline water is one of the major natural disasters in coastal regions. The study area Thoothukudi district is situated on the east coast of India and faces saline water vulnerability threats from both natural and anthropogenic activities. The district has many chemical industries, heavy water plants, and salt pans along the coast, besides, the city is becoming an important trade center for import and export. The development of industrial activities emphasizes the need for periodical assessment and monitoring of fresh groundwater potential sources and saline water intrude zones for sustainable management. To assess groundwater potential, saline water intrusion, and fresh-saline water interface, the geophysical electrical resistivity technique is widely adopted to understand subsurface geological formation. In this attempt, saline water intruded zones are demarcated using electrical resistivity scanning technique from Vaippar River to Tambaraparani River of Thoothukudi district, Tamil Nadu, India. The study area is located between the North latitude of 8° 30′ to 9° 10′ and the East Longitude of 77° 50′ to 78° 20′ and the extent is about 550sqkm. Geologically, the area comprises subrecent to recent age of coastal sand, clay, kankar, and clayey sand, tertiary calcareous sandstone with and without shells, and archean hornblende biotite gneiss, quartzite. Major geomorphologic units are pediplain, coastal, and alluvial plans. The multielectrode electrical resistivity scanning was carried out at 29 locations using the SSR-MP-AT-ME model resistivity meter. The scanning was carried out for a length of 100m using 50 electrodes at an interspacing of 2m. The obtained resistivity data were transferred using IGIS scan software and analyzed using surfer software. Geoelectric layers were distinguished from resistivity variation and saline water zones were delineated resistivity of ≤ 10ohmm. Iso-resistivity maps and overlay analysis of water level, rainfall, geology, and land-use patterns were done in GIS. The study indicates intrusion of saline water exists in the study area and the interface is about 10km from the coast. Regulating salt pans, exploring water from deep aquifers, and implementing groundwater recharge structures will control saline water movement and improve freshwater resources.
Published Version
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