Modeling Flow and Solute Transport in Fractured Porous Media at Jinping I-Hydropower Station, China

Abstract

A model that couples the rock matrix and fracture flow is employed to simulate the flow and solute transport in fractured porous media. The porous matrix is represented using an equivalent continuum model, and discrete fractures are described using a discrete-fracture network model. Data on the fracture properties were collected from the study area to randomly generate the fractures. The model was calibrated and validated using the measured groundwater levels and tracer test data. The results indicate that the groundwater levels and concentrations simulated using the coupled model agree well with the observed data. In contrast, those obtained using the continuum model for the entire domain do not. In the fracture areas in which abnormal groundwater levels were observed (i.e., where the level was lower than the Yalong River stage), the coupled model effectively captures and replicates the primary geological and hydrogeological characteristics. Once again, the continuum model results do not. A sensitivity analysis of the parameters showed that an order of magnitude variation in the hydraulic conductivity corresponds to a 0.05–0.13% variation in groundwater levels, implying that changes in hydraulic conductivity have little effect on groundwater level. Additionally, a half order of magnitude increase or decrease in the dispersion parameters leads to a 0.6–4.26% variation in concentration. Thus, the response of the concentration to changes in dispersion parameters is not significant.