Risk analysis using stochastic reliability methods applied to Jinan district groundwater quality model

摘要

A landfill site may cause groundwater contamination when its leachate moves into the underlying aquifer through the unsaturated zone. To assess the risk of groundwater contamination quantitatively, we need a coupled groundwater flow and mass transport model of the site. Due to the complexity of natural geological formations, accurately modeling the contaminant transport process in a heterogeneous aquifer is very difficult. The uncertainty of model prediction may be caused by the uncertainties in model structure, model parameters, infiltration factors, discharge and precipitation rates, as well as boundary conditions. In this study, we use the Monte-Carlo Simulation (MCS) to assess the probability of failure for risk analysis. The sampling region is determined by the results of groundwater flow model calibration and sensitivity analysis. As a case study, the presented process is employed to assess the contamination risk of the Jinan basin, which is famous for its beautiful Well Complex. When a hypothetical landfill site was conducted in the upstream area of the basin, the arrival time to the city area is calculated by our calibrated model. The uncertainties of these calculation results are then estimated. It is found that the contaminant would arrive the springs located in the city center in a short time period about 80 years.