A Quasi-Three-Dimensional Variably Saturated Groundwater Flow Model for Climate Modeling

Abstract

Abstract In this study, a quasi-three-dimensional, variably saturated groundwater flow model was developed by approximately dividing the three-dimensional soil water and groundwater flow into an unsaturated vertical soil water flow and a horizontal groundwater flow to simulate the interactions among soil water, groundwater, and vegetation. The developed model consists of a one-dimensional unsaturated soil water flow model with the water table as the moving boundary using an adaptive grid structure for a vertical soil column formed based on discrete grid cells in a horizontal domain, a two-dimensional groundwater flow model for the horizontal domain, and an interface model connecting the two components for the horizontal grid cells in the domain. Synthetic experiments by the model were conducted to test the sensitivities of the model parameters of river elevation, ground surface hydraulic conductivity, and surface flux, and the results from the experiments showed the robustness of the proposed model under different conditions. Comparison of the simulation by the model and that by a full three-dimensional scheme showed its feasibility and efficiency. A case of stream water conveyance in the lower reaches of the Tarim River was then applied to validate the developed model for simulation of the water table elevations at the Yingsu section. Finally, a numerical experiment by the model for the Tarim River basin was conducted to discuss the groundwater latent flow for large-scale high-relief topography with stream water conveyance. The results show that the model can simulate the water table reasonably well.