This book explains how to design a groundwater model using the accompanying customized DesignMod software. DesignMod does not require a digitizer, but instead uses the mouse and rich graphical features of the Windows environment. It enables the user to draw and redraw easily and quickly cross sections and plan views with site base map information, contour, and zonation pattern overlays. Discretization, aggregation, averaging, and approximation guidelines for designing groundwater models with DesignMod are provided as a handy reference. DesignMod also can be used to manipulate and view model database array files. Many exercises with step-by-step program operation documentation are provided for beginning and intermediate modelers.