Quantifying Groundwater Availability and Hydrological Status Using Visual MODFLOW in Siliguri Planning Area, a Terai Region of Darjeeling Himalaya, India

The environmental water balance is threatened due to the massive extraction of freshwater resources for daily human consumption around the world. This study endeavors to incorporate Visual MODFLOW, remote sensing and GIS techniques to establish a computational simulation of groundwater flow and quantify groundwater availability in the Siliguri Planning Area, which is facing rapid urbanization and high population growth. The basic parameters of MODFLOW modeling, such as observation heads and wells, boundary conditions and layer properties, are prepared from data issued by different sources. A model was designed to enhance our understanding of the three-dimensional hydrogeologic system of aquifers and simulate current and future groundwater behavior. Model performance was evaluated using more statistical indicators, including mean absolute error (MAE = 0.386 m), root mean square error (RMSE = 0.466 m) and coefficient of determination (R 2 = 0.9826), which indicate good agreement between observed and simulated groundwater levels. Recharge is primarily controlled by monsoonal precipitation and LULC characteristics, with agricultural and vegetated areas contributing 60–70% of total recharge, while built-up areas contribute less than 20%. Temporal analysis indicates localized groundwater decline at a rate of 0.16–0.18 m/year in urbanized zones. The groundwater recharge in the study area ranges from 5000 to 10,000 hectare-meters (ham), while groundwater extraction ranges from 1000 to 1500 ham. Overall, the net groundwater availability across all layers is 10,430 hectare-meters (ham). The findings may help groundwater authorities and associated organizations better comprehend the possible state of groundwater resources and put adaptation plans into place to prevent the loss of the water resources.