Application of Visual MODFLOW in Groundwater Flow Modeling at the Left Crescent of the Ganga River, Varanasi, India

Abstract

Groundwater flow modeling is a significant tool for conceptualizing the hydro-geological processes and forecasting the groundwater pollution. To simulate the groundwater flow direction and pollutant fate, Visual MODFLOW and MODPATH are used popularly. Present study focuses on the application of Visual MODFLOW to study the groundwater flow direction, groundwater flow path lines and to predict the leachate contamination from the open unsecured MSW dumping site at the left crescent of the Ganga River in Varanasi, India. Simulation of the model is done for one year by giving input value to the flow setting and transport setting database of the software to know the groundwater flow direction and flow velocity in the study area. Linear isotherm (equilibrium-controlled) with no kinetic reactions is assumed for contaminants transport modeling. The simulated result indicates that the groundwater is flowing from higher heads (water table) to lower heads (towards Ganga River) in the study area. The maximum velocity of groundwater flow is calculated to be 5.7E-06 m/s (5.7 × 10−7 m/s). Simulated groundwater table was ranged from minimum 58 m to maximum 74.93 m. This result is validated with the field monitoring data of water table which was also observed to be between 61.96 m and 78.85 m. TDS transport model results indicate the movement of TDS pollutant towards the groundwater flow direction. TDS transport modeling showing a distinct pollutant path line from MSW dumping site to nearest observed heads (wells) and its path lines are congruent with the groundwater flow direction. This study would be helpful for site-suitability index for landfill strategy makers and the government authorities to safeguard groundwater pollution from potential risk from the landfill. © Springer Nature Singapore Pte Ltd. 2021.