Importing Data from MODFLOW or MODPATH Graphic Groundwater can import some types of MODFLOW and MODPATH input files. These files must be in the text input format described by McDonald and Harbaugh (1988) and Pollock (1989). Newer versions of MODFLOW support other input formats, but Graphic Groundwater does not. Basic model information necessary for Graphic Groundwater to construct a grid are contained in the input files for the Basic and Block-Centered Flow packages of MODFLOW. Therefore, both of these packages must be imported while in Grid mode. The Import MODFLOW Packages commands under the File menu displays the commands necessary to import these packages. The Basic package must be imported first. Once the Block-Centered flow package is successfully imported, Graphic Groundwater will shift to Model mode and display the grid. The stress input files (Drain, Evapotranspiration, General Head Boundary, Recharge, River, and Well packages) are imported in Model mode, with commands for each stress displayed by the Import MODFLOW Packages command under the File menu. You can import stress package input files into any grid as long as none of the stresses have columns, rows, or layers outside of the grid domain. MODPATH cell stress input files are similar to those for MODFLOW, but the MODPATH files contain an extra parameter at the end of every line, the discharge face (IFACE), a flag that indicates how budget terms are to be handled; as internal sources or sinks or assigned to specific cell faces (consult Pollock, 1989). Graphic Groundwater can read either MODPATH or MODFLOW cell stress input. The program can also import MODPATH or MODFLOW area stress files and extract information on how these stresses are distributed in a cell (the parameter ITOP in a MODPATH input file). The MODPATH main file often contains information not contained in any MODFLOW file, such as top and bottom elevations for model layers. Graphic Groundwater can read data from a MODPATH main input file, but only imports the type of grid (IGRID), number of confining beds (NCBL), the confining bed codes (NCON) for each layer, the model and confining layer thicknesses (DELZ and DELCB) if the grid is regular (IGRID=1), and the top and bottom elevations of model layers for irregular grids (IGRID=0). All other information is ignored. Graphic Groundwater cannot import data from other MODFLOW and MODPATH input files. These files either contain trivial information that can be easily entered into Graphic Groundwater, or the package features are not yet implemented in Graphic Groundwater. For example, it is easy to set the strongly implicit procedure or conjugate gradient procedure parameters in the Solver Packages Preferences window. Graphic Groundwater also makes it easy to set the location of particles for particle tracking.