Groundwater is an important resource so it must be managed prudently. However, there are several difficulties associated with understanding a groundwater system. Its invisibility and highly heterogeneity nature has made it very difficult to accurately characterize the media in which the groundwater is stored. One way of improving our understanding of these highly complex systems is to build and experiment with models which replicate them. A model is a simplified representation of the complex natural world. For example, a road map is a kind of model (Wang and Anderson, 1982); it depicts a complex network of roads in a simplified manner for purposes of navigation. Similarly, a conceptual model of a groundwater system simplifies and summarizes what is known about the hydrogeology in the form of written text, flow charts, cross sections, block diagrams, and tables. A conceptual model is an expression of the past and current state of the system based on field information from the site, and knowledge available from similar sites. A more powerful groundwater model is one that quantitatively represents heads in space and time in a simplified representation of the complex hydrogeologic conditions in the subsurface. Broadly speaking, groundwater models can be divided into physical (laboratory) models and mathematical models. There are two principle drivers behind most modeling exercises. First, to gain an understanding of why a system behaves as it does and second to predict future behaviour (Fetter, 1988; Anderson and Woessner, 2002). Anderson and Woessner (2002) add a third dimension as a tool to provide solution and regulatory guidelines for improvements and corrective measures. Models can help the designer to understand a system’s behaviour through the iterative process by which the model is modified until the results generated match field results. It is important to clearly establish the purpose of the model.