Introduction. Equations and Numerical Methods. The Conceptual Model and Grid Design. Boundaries. Sources and Sinks. Profile Models. Special Needs for Transient Simulations. Model Execution and the Calibration Process. Documenting and Reporting Your Modeling Study. Postaudits: How Good Are Predictions? Particle Tracking of Groundwater Flow and Advective Transport of Contaminants. Advanced Topics. Chapter References. Index.