Simulation of Groundwater Flow in an Unconfined Sloping Aquifer Using the Element-Free Galerkin Method

Numerical simulation of groundwater flows in real aquifers has been commonly based on Finite Difference (FDM) and Finite Element Methods (FEM). These mesh-based methods require a computational grid, which can be costly to generate in case of complex geometries and can significantly increase the computational cost when adaptive remeshing is required. This work presents the Element-Free Galerkin Method (EFGM) for solution of the groundwater equation and demonstrates its application to a real unconfined sloping aquifer. EFGM uses the Moving Least Square (MLS) method for approximating the unknown head and computing the EFGM shape function, leading to increased accuracy, stability in function approximation and higher convergence rate than mesh-based methods. In the present study, EFGM is initially applied to one- and two-dimensional hypothetical problems, and validated with analytical solutions. Subsequently, EFGM is applied to the simulation of groundwater flow in the Blue Lake Aquifer (BLA) in North California, and the simulation results are compared with those obtained using MODFLOW. The results demonstrate the potential of EFGM for analyzing real aquifer problems.