GMS includes a comprehensive graphical interface to the groundwater model MODFLOW 2000. MODFLOW is a 3D, cell-centered, finite difference, saturated flow model developed by the United States Geological Survey (McDonald & Harbaugh, 1988). MODFLOW can perform both steady state and transient analysis and has a wide variety of boundary conditions and input options.

GMS supports the Observation (OBS), Sensitivity (SEN), and Parameter Estimation (PES) processes in addition to the new Layer Property Flow (LPF), Hydrogeologic Unit Flow (HUF), and Direct Solver packages. All other popular packages are supported, such as the HFB and Stream packages. GMS reads and writes native MODFLOW files so you will always have a transferable model!

A special version of MODFLOW is distributed with GMS. Both the source code and executable are included. This version of MODFLOW is the same as the version distributed by the USGS except for a few minor changes primarily related to file input. These changes are clearly marked in the code.