Evaluation of aquifer vulnerability in a coal mining of India by using GIS-based DRASTIC model

The objective of this study is to estimate the aquifer vulnerability in the West Bokaro coalfield, Jharkhand, India, by using a geographic information system (GIS)-based DRASTIC model. The DRASTIC model incorporates seven hydrogeological data, i.e. depth of water table, net recharge, aquifer media, soil media, topography, impact of vadose zone and hydraulic conductivity. The model was validated by comparing the model output (vulnerability index map) with a statistical analysis and the actual SO42- and Fe concentrations in the groundwater of the study area. Thirty-three well samples were collected from the West Bokaro coalfield area. These were analyzed in the laboratory to measure the level of SO42- and Fe in the groundwater. The GIS-based DRASTIC result showed that 0.06 % of the area fell into the low-vulnerability zone and 10.8 % fell into the moderate vulnerability zone. About 87.7 % of the study area fell into the moderate to high-vulnerability zone, and 1.4 % of the study area was classified as the highly vulnerable zone. From the vulnerability map, it was observed that some of the western part and some of the middle part of the study area lay in the high-vulnerability zone, and therefore, they were more susceptible to aquifer pollution. The geogenic and anthropogenic activities are responsible for the high vulnerability in the study area. The shallow water level, topography, high net recharge and permeable vadose zone of the area served as the major influential parameters in mapping the vulnerability. The mining and related activities are also responsible for the high aquifer vulnerability of the area. The aquifer vulnerability maps generated in this study could also be used for the management of future water resources and environmental planning in all the mining regions.