Simulation of Groundwater Flow around a Waste Landfill Site

Waste landfill sites in Japan are constructed in mountainous regions because the Japanese population is concentrated in limited flat areas. Consequently, waste landfill locations necessarily correspond with water resources areas. Therefore, we need to evaluate previously the influences of contaminants leached from waste landfill sites when it is newly constructed. For this purpose, it is important to predict the groundwater movement accurately because the contaminants are diffused and advected in groundwater. In this study, we simulated the groundwater flow around a waste landfill site using MODFLOW which was a software package.The groundwater levels around a waste landfill site have been measured to verify the accuracy of simulation results. The target area, which was 750m*450m, was modeled by a GIS tool which was contained in GMS (Groundwater Modeling System). The cell size for finite difference was 15m*15m. The model parameters were adjusted, comparing the simulated groundwater levels with the measured ones. The results were as follows: The variations of groundwater levels were predicted reasonably using the relationship between the measured groundwater levels and rainfalls. The groundwater levels in the upper area were simulated within appropriate ranges and the variations of simulated groundwater levels showed the same tendency as those of the measured ones. On the other hand, the simulated water levels in the lower area were overestimated and over the soil surface. In the future study, we need to simulate the groundwater considering that the topography and layers of the site is very complicated, compared with the previous works used in the MODFLOW.