Assessment of groundwater vulnerability using modified DRASTIC model in Kharun Basin, Chhattisgarh, India

An application of remote sensing and geographic information system (GIS) has become one of the essential techniques in the field of hydrogeological science that helps in assessing, monitoring, conserving, and managing groundwater resources. In the present study, modified DRASTIC model has been used to access the groundwater vulnerable zone of Kharun Basin. The modification has been done by replacing hydraulic conductivity parameter to land use. The aim of this study is to determine susceptible zone for groundwater pollution by integrating hydrogeological layers in GIS environment. The final index map shows that the resulting index value varies from 86 to 191; further, the zones are divided into five classes. The results showed that out of the total area of 4191 km(2), an area of about 8, 197, 2730, 1229, and 27 km(2) lies in very low, low, moderate, high and very high vulnerable zones, respectively. Sensitivity analysis is also performed in this study, and it reveals that depth of water table, land use, and topography parameters cause large variations in vulnerability index as compared to other parameters. Moreover, land use and topography were found to be more effective parameters in assessing groundwater vulnerability than assumed by original model. Model validation shows a good correlation between nitrate sample and resulting DRASTI-LU index. This study produces a very valuable tool for policy makers as it reveals a very comprehensive indication of vulnerability to ground water contamination. The knowledge about high vulnerable zone is important for local authorities to manage and monitor groundwater resources.