Global Land Surface Modeling Including Lateral Groundwater Flow

Abstract The groundwater system is an essential part of Earth's systems. However, most current land surface models (LSMs) for climate modeling do not explicitly account for the lateral groundwater flow process. In this study, schemes describing LSM‐lateral groundwater flow module coupling, model resolution conversion, and parallel simulation were designed and implemented to incorporate a lateral groundwater flow module into the Community Land Model 4.5. The depth to less permeable bedrock also was included in the large‐scale groundwater flow modeling. Model validation was performed using multiple observations from the 20‐year continuous groundwater table depth measurements at 67 stations in 10 countries, 1.6 million worldwide time‐averaged groundwater table depth measurements, previous knowledge about the locations of major aquifer systems, and inversed terrestrial water storage anomalies derived from satellite data. The simulated results show that the groundwater table pattern is a combined reflection of climatic and topographic factors across a range of spatial scales. Lateral groundwater flow significantly modified the equilibrium water table patterns in North Africa, the Arabian Peninsula, central Asia, and southern Australia, deepening the water tables by more than 6 m. The trend of deepening groundwater tables observed between 1970 and 2010, which was found to be 0.025 to 0.125 m/decade, was exacerbated by the lateral flow; however, the seasonal variability of the groundwater table depth was reduced by the buffering effect of the lateral flow.