Groundwater mixing dynamics play a crucial role in the biogeochemical processes of aquifer systems. As a fundamental component of the hydrologic cycle, evaporation is critical driver for the exchange of water and energy fluxes between the surface and subsurface. Thus, it affects groundwater flow and associated solute transport processes in aquifers. In this work, we developed a numerical model to simulate the effects of evaporation on groundwater flow and solute transport process, coupling surface aerodynamics and subsurface flow dynamics. Evaporation was simulated utilizing a bulk aerodynamic model. Groundwater flow and solute transport processes were simulated utilizing a two-dimensional finite element groundwater MARUN, taking into account variably saturated, density dependent conditions. Our results indicate that evaporation could generate significant upwelling groundwater flow and therefore cause solutes to migrate from deep sediment to the surface. As the solute reaches the surface, evaporation enhances the accumulation of the solute near the surface, resulting in a higher solute concentration than in deep sediments. In coastal aquifer systems, evaporation, interacting with density gradients and oceanic forcing (e.g., waves and tides), likely creates a complex driving mechanism that affects coastal groundwater flow and salinity dynamics.
