Evaluation of Aquifer Vulnerability Using Drastic Model and GIS: A Case Study of Mysore City, Karnataka, India

Abstract

This investigation was carried out to determine the aquifer vulnerability using DRASTIC method which correlated well with the physico-chemical characteristics of groundwater in Mysore city. The main objective was to determine the susceptible zone for groundwater pollution by integrating hydrogeologic layers in Global Information System (GIS) environment. The methodology entailed documentation stage followed by field phase involving collection of 53 groundwater samples from the study area during pre and post monsoon seasons. The layers such as depth to water-level, recharge rate, aquifer media, soil permeability, topography, impact of vadose zone and hydraulic conductivity were integrated in the DRASTIC model using GIS spatial analysis tools and techniques. The aquifer analysis highlighted that the vulnerability range were with from < 70 and > 100. It was found that, when the net recharge is high, the vulnerability was also found very high. The nitrate concentration in groundwater was within the WHO permissible limit in the pre monsoon, in 95% of the samples. But, in the post monsoon season, 70% of the samples exceeded the permissible limit. A positive correlation was observed between groundwater vulnerability and concentration of nitrate in groundwater. GIS application of the DRASTIC model was found to be a suitable method for analyzing the groundwater vulnerability in a city environment like Mysore.