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Introduction
Groundwater is the major source of freshwater that caters to the domestic water demand arising due to escalating population and modern agricultural practices in many developing countries. Groundwater is generated through a large number of borewells, tube wells and dug wells, which are spread in the agricultural fields, residential areas, and industrial areas. The heavy withdrawal of groundwater has resulted in lowering of groundwater levels, which in turn has caused deterioration in groundwater quality. The continuing groundwater exploitation has not only resulted in lowering of groundwater levels but also increased the wide variation in the zone of fluctuation. The withdrawal has led to several quality-related problems. The geological structures play a major role in the groundwater flow and quality-related problems. The geologic structures like dykes, lineaments, and fractures act as both carriers as well as barriers for groundwater flow. There have been many studies/ technical reports showing the role of dykes in controlling the groundwater flow in an area (Nilsen et al.2003; Al-Taj 2008; Perrin et al.2011). Several researchers have used spatial distribution of geology, geomorphology, landuse, drainage, and lineaments to identify groundwater potential zones (Srinivasa and Jugran 2003; Nag 2005; Mondal et al.2007; Vasanthavigar et al. 2011). Many researchers have also reported that dykes that behave as barriers have quality-related problems in the upstream side (Srinivasa and Jugran 2003; Nag 2005; Mondal et al. 2007). One such study was carried out in the northern part of Tirunelveli district, south India where groundwater flow and quality is mainly controlled by the geological structures. Few hydrogeological studies have been carried out by researchers of Central Ground Water Board from time to time to appraise the groundwater scenario of the area (Vardaraj 1984; Kunhambu 1990; Sampath Kumar 1994; Senthilkumar 2010). The present study was carried out to investigate the effects of geological structures on groundwater movement and quality.
Methodology
Detailed hydrogeological survey was carried out during May 2010. In order to understand the hydrogeological setting of the region, the available geological maps and existing reports were studied. As there were some data gaps, an intensive geological investigation was carried out in the study area, to study the nature of the rock, topographical expressions, intensity and depth of weathering, and demarcation of...