Groundwater vulnerability assessment using GIS-based DRASTIC model in the upper catchment of Dwarakeshwar river basin, West Bengal, India

In the recent years, ground water vulnerability or more specifically contamination of unconfined aquifer has been intensified due to multiple reasons. A GIS-based DRASTIC model was used for assessment of groundwater vulnerability on upper Dwarakeshwar river basin, India. Seven intrinsic hydro-geological parameters like depth of water table, net recharge, aquifer media, soil media, topography, the impact of vadose zone and hydraulic conductivity were considered to assess the magnitude of vulnerability. Different weights and ratings were assigned according to their relative significance and successfully running of the model. Data were collected from 34 different locations within the basin and DRASTIC Vulnerability Index (DVI) was applied to identify the ground water vulnerable zones. DVI values show the range from 90 to 170 and it was classified into five zones such as very low, low, moderate, high, and very high, respectively. Here, ArcGIS 10.4 software was used to design the various digital thematic maps. The GIS analysis shows that around 1.18%, 11.87%, 60.93%, 23.41%, and 2.61% areas fall under very low, low, moderate, high, and very high vulnerable zones respectively. Statistical analysis such as single parameter sensitivity analysis and map removal sensitivity analysis show that the depth of water table is the most sensitive parameter for groundwater contamination in the study area. Validation of this model was checked by K+ concentration in the groundwater sample of the study area which indicates very high correlation (R2 = 0.94) with the DRASTIC vulnerable zones. The overall analysis indicates that the near-surface aquifers are most vulnerable to the contamination in upper Dwarakeshwar river basin area. This scientific study will definitely assist to the regional planners and policy makers for sustainable ground water development and management.