Assessment of groundwater nitrate vulnerability using DRASTIC and modified DRASTIC in upper catchment of Sabarmati basin

Contamination from agriculture diffuse particularly nitrate is an important concern due to its impact on groundwater quality and human health. To ensure the protection of groundwater and effectively improve the quality of life, an overlay index-based method is proposed by taking into consideration of all pollution sources that causes potential risk to the resource in this study. A comparison had been presented between the original DRASTIC and DRASTIC-L (land use) to identify the suitability of model for probability of pollution occurrence which help in optimizing the drilling activities and safeguarding the resources. The outcome of the result is categorized into five vulnerability classes which shows that 25.9% of the total study area is extremely sensitive due to overdraft of groundwater and contamination from agriculture and industrial diffuse. The effectiveness of model was validated with correlation (r2) among water quality parameters and DRASTIC index (DI). Moreover, to exhibit better finding in terms of the specific vulnerability to agriculture contamination (NO3−) in the aquifers, DRASTIC-L was adopted in which above 50% samples exceeded WHO water quality permissible limit. The efficiency of both methods was quantitatively assessed based on the correlation of nitrate, which was improved from r2 of 0.40–0.57. The finding suggests that though the depth of water is relatively shallow as compared to central Gujarat, future overexploitation at vulnerable zones should be carefully monitored.