MAGNET is a groundwater flow and mass transport model. It consists of two parts, the mathematical model and a graphical user interface (GUI). The model is a computer program that solves using numerical methods the equations that describe groundwater flow and mass (contaminant) transport. The GUI is a user-friendly computer interface that facilitates putting the physical and chemical information that the model needs into computer-readable form. It also organizes the input and output information in a format that is amenable to presentation in a graphical format (e.g. contours of equal concentration or water levels).