Three-dimensional numerical simulation of fully coupled groundwater flow and land deformation due to groundwater pumping in an unsaturated fluvial aquifer system

A series of three-dimensional numerical simulations using a hydrogeomechanical numerical model is performed to analyze and predict fully coupled groundwater flow and land deformation due to groundwater pumping in an unsaturated fluvial aquifer system, which has irregular lateral boundaries. The aquifer system is composed of a loam layer underlain by a sand layer on bedrock. A steady-state numerical simulation is performed first to obtain initial spatial distributions of pressure head, hydraulic head, and groundwater flow velocity before groundwater pumping, and its results are illustrated and validated reasonably with respect to field measurements of hydraulic head. A transient-state numerical simulation is then performed to obtain spatial and temporal distributions of pressure head, hydraulic head, groundwater flow velocity, and land displacement vector during groundwater pumping, and its results are also illustrated and validated reasonably with respect to field measurements of both hydraulic head and vertical displacement. These numerical simulation results show that hydrogeomechanical numerical modeling can be a useful tool for analyzing and predicting long-term groundwater level fluctuation and land deformation due to groundwater pumping in actual three-dimensional aquifer systems.