Simulation of Fluoride Migration in Groundwater of the Affected Areas of Shilabati Riverbank, West Bengal, India

To obtain insightful knowledge about the migration pathway of fluoride and the transport phenomenon in the subsurface environment, a three-dimensional conceptual contaminant fate and transport model was developed using numerical groundwater modelling software (Visual MODFLOW 6.0). The conceptual model relied on the measured hydro-geological data and boundary conditions related to hydraulic conductivity, storage coefficient, specific yield, general head, recharge and river boundary. The model calibration yields a linear correlation coefficient of 0.978 for flow model and 0.947 for the transport model. Sensitivity analysis of the calibrated model shows that migration of fluoride is more susceptible to changes in hydraulic conductivity than other input parameters. From the scenario analysis of the conceptual model, different rates of fluoride migration in different stratigraphic layers of the aquifer have been observed. The simulation results inferred that horizontal migration of fluoride had made the surroundings of the contaminated aquifer unsafe for drinking water and irrigation purposes. From both scenario and sensitivity analyses, it has been found that some common hydrologic phenomenon prevails in subsurface environment of the study area that leads to enrichment and migration of fluoride from the contaminated zone to the other part of the model domain along with groundwater flow.