Import MODFLOW Packages – Basic Package The Import MODFLOW Packages – Basic Package command displays the standard Windows Open File dialog box. Only files with a bas file extension are shown. The file must be in text format and in the standard input format for the MODFLOW basic package. Select a file and click on the Open button. Graphic Groundwater will then import the MODFLOW basic package file which contains information on an existing MODFLOW model. This command must be followed by the Import MODFLOW Packages – Block Centered Package. Consult Chapter 4 for more information on this command.