What is Ground-Water Flow Modeling?
Models are simplified descriptions of physical reality and can be verbal descriptions, graphical representations, physical models, or mathematical equations. Mathematical equations, such as the ground-water flow equation, can be solved efficiently by computer programs. The ground-water flow equations are solved on a computer by two main methods—by finite differences and finite elements. Both of these methods solve the ground-water flow equations for a conceptual model (fig. 3A) across a model grid. To model a ground-water system (fig. 3A), it is divided into discrete units, or cells, consisting of a grid system with one or more layers or dimensions (fig. 4). Finite-difference grids are regular rectangular grids (fig. 3B) and finite-element grids are irregular polygonal subdivisions (fig. 3C); these grid types reflect the mathematical techniques used to solve the ground-water flow equations. These grids can represent one-, two-, or three-dimensional systems (fig. 4). Computerized numeri
