Water exchange between the surface and subsurface is important for both water resource management and environmental protection. In this paper, we develop coupled surface and subsurface flow simulation capability in a parallel subsurface flow and reactive transport code PFLOTRAN. We sequentially couple the diffusion wave-based surface flow with the subsurface flow governed by the Richards equation in PFLOTRAN. These two flow domains are linked with a boundary condition switching method that ensures the continuity of pressure and flux at the surface-subsurface interface. We verify the coupled code against other existing hydrologic models and observation data using a number of numerical experiments. The coupled hydrological model exhibits good performance in strong parallel scaling tests. The new coupled surface and subsurface simulator significantly advance community simulation capability towards improving integrated hydrologic and biogeochemical understanding of complex systems such as watersheds and river corridors.

地表与地下之间的水交换对于水资源管理和环境保护都至关重要。在本文中，我们开发了平行地下流动和反应输运代码PFLOTRAN的地面和地下流动耦合模拟功能。我们依次将基于扩散波的表面流与由PFLOTRAN中的Richards方程控制的地下流耦合。这两个流动域与边界条件转换方法相关联，该方法确保表面和地下界面处压力和通量的连续性。我们使用许多数值实验，对照其他现有水文模型和观测数据验证了耦合代码。耦合水文模型在强大的并行缩放测试中表现出良好的性能。