Chapter 1 Introduction Graphic Groundwater is a graphical interface for the United States Geological Survey (USGS) groundwater modeling programs. This version of Graphic Groundwater runs under Microsoft Windows environments and supports the modular three-dimensional finite-difference groundwater flow model (MODFLOW; McDonald and Harbaugh, 1988) and some features of the particle tracking program (MODPATH; Pollock, 1989; 1994). The program is designed to simplify model development and data input for groundwater modeling, to let you develop maps and diagrams within Graphic Groundwater, and to provide graphic and text files which can be processed outside Graphic Groundwater. This introductory chapter describes the hardware and software requirements for running Graphic Groundwater, as well as how to install the program on your computer. Other chapters help you create a simple groundwater flow model; define each command; explain powerful graphics features and how the program takes advantage of the Windows operating system; and describe technical aspects of Graphic Groundwater.