Assessment of Groundwater Vulnerability Using GIS and DRASTIC for Upper Palar River Basin, Tamil Nadu

ABSTRACT Groundwater is one of the valuable resources and due to increase in the population, industrialization and agriculture practices, the groundwater stress has increased to a greater extent. Once the groundwater gets contaminated, remediation is very difficult. The steps to measure the groundwater vulnerability must be taken for sustainable groundwater protection and management planning. In this paper, the DRASTIC model is applied to find out and generate a small-scale map of groundwater vulnerability to assess the contamination in the upper Palar river basin, Tamil Nadu, India. A number of tanneries are located along the banks of the river basin. The quality of groundwater in and around river basin area has been affected very much due to the untreated effluent of the tanneries discharged directly to the river. The DRASTIC model consists of seven hydrogeological parameters including depth to water table, net recharge, aquifer media, soil media, topography, impact of vadose zone and hydraulic conductivity; each factor is assigned by weight and rating which depends upon the influence of the seven hydrological layers of the river basin area. The ArcGIS 10.3 software was used to create the groundwater vulnerability map by overlaying the seven layers, which is intended to show potential areas of groundwater contamination. The results of the study shows that, 50% of the study area falls under very high pollution potential zone, 20% under high pollution potential, 15% under moderate pollution potential, 10% under low pollution potential, and the remaining 5% of the area has no risk. The very high vulnerability class which is covered by the alluvium along the river course is most likely to pollution due to the very lower slope terrains in the direction of the central part, which allows better percolation of contaminants into the groundwater. The low vulnerability class lies in the area covered by the hard rock and clay loam soil in the upper reach of the Palar river which contains mountains and hard rock terrain.