iMOD (since 2006) is an easy to use Graphical User Interface + an accelerated Deltares-version of MODFLOW with fast, flexible and consistent sub-domain modeling techniques.iMOD facilitates very large, high resolution MODFLOW groundwater modeling and geo-editing of the subsurface. Key features of iMOD are:
iMOD is open source since June 2014.The Fortran source code of the iMOD GUI and the accelerated Deltares-version of MODFLOW is available. You can include your own features and re-compile your executable (Winteracter and OpenGL libraries required).
Click here to download iMOD 5