Author(s): Zhibo Zhang; Zhi Li
Linked Author(s): Zhi Li
Keywords: Subsurface contaminant simulation Fully integrated numerical model Model verification
Abstract: The unsaturated zone serves as a critical nexus for the exchange of water and energy between atmospheric water, surface water, and groundwater, acting as the source of sustenance for terrestrial plants and a conduit for surface pollutants to infiltrate groundwater. It holds significant importance within the entire hydrological cycle system. The movement of soil moisture is extremely complex, making it crucial to accurately describe the laws of water and solute transport in saturated and unsaturated zones, and to efficiently assess the impact of soil water and solutes on the groundwater environment. Simulations of soil water and solute transport in the unsaturated zone primarily rely on numerical methods based on Richards equation and the convection-dispersion equation, as well as various simplified methods. However, the strong nonlinearity of Richards equation imposes strict requirements on spatial and temporal step sizes for numerical solutions, leading to high computational costs. Due to the differences in movement characteristics between saturated and unsaturated zones, there are relatively few models that adopt a fully coupled approach. High-performance computing (HPC) technology, as a powerful tool, has become an effective means of enhancing computational efficiency. This study, based on the existing high-performance groundwater dynamics model SERGHEI, develops a fully integrated model for saturated-unsaturated solute transport using a heterogeneous programming framework model, aiming to achieve efficient numerical simulation of the entire process of groundwater movement and solute transport. By combining classic examples from literature, the results were validated against existing groundwater solute transport models HYDRUS data, showing that the developed model can reasonably calculate water flow and solute transport processes even under complex boundary and variable soil conditions. Furthermore, simulation speed tests of the coupled model under conditions such as single-core, multi-core CPUs, and multiple GPUs indicate that the model can efficiently simulate water flow and solute migration at the regional scale with relatively low computational costs.
Year: 2025