10.1 Introduction

The word ‘model’ is used frequently in hydrogeology as in all the natural sciences. It is used both as a noun (“… develop a model of a system…”) and as a verb (“… use an equation to model a system…”). This word means a lot of different things to a lot of different people; to some, it is a computer program that simulates a natural process, to others it a scaled‑down physical representation of an object—like a model car or a model solar system used in a classroom—and to some it refers to tall, attractive, exotic‑looking people that display the latest clothing styles on runways in Paris. We won’t be dealing with the latter in this section. However, the concept of models is something that has applications in all the sciences, and it is important that we define what it means in general and what it means to hydrogeologists in particular.

In this section, we discuss the idea of modeling groundwater flow systems at the highest level with the objective of providing the most general overview of the subject. At the end of the section, we present references and suggestions for additional training and education related to developing and using computer groundwater flow models.