Changing depth to water table and the associated stored water volume is a crucial component of the global hydrological cycle, with impacts on climate and sea level. However, long-term changes in global water-table distribution are not well understood. Coupled ground- and surface-water models are key to understanding the hydrologic evolution of post-glacial landscapes, the significance of terrestrial water storage, and the interrelationships between freshwater and climate. Here, I present the Water Table Model (WTM), which is capable of computing changes in water table elevation at large spatial scales and over long temporal scales. The WTM comprises groundwater and dynamic lake components to incorporate lakes into water-table elevation estimates. Sample results on both artificial and real-world topographies demonstrate the two-way coupling between dynamic surface-water and groundwater levels and flow.