MODFLOW is a modular hydrologcial model that allows users to simulate and project groundwater condition and groundwater/surface-water interaction to inform management and policy decisions for the sustainable and productive use of these water resources.


MODFLOW is the USGS's modular hydrologic model. MODFLOW is a popular open-source groundwater flow model considered an international standard for simulating and predicting groundwater conditions and groundwater/surface-water interactions. The model has been in use for over 30 years with continued refinement driven by the growing need to understand surface and ground water interactions.

MODFLOW was originally developed and released solely as a groundwater-flow simulation code when first published in 1984. The models modular structure has provided a robust framework for integration of additional simulation capabilities that build on and enhance its original scope. The family of MODFLOW-related programs now includes capabilities to simulate coupled groundwater/surface-water systems, solute transport, variable-density flow (including saltwater), aquifer-system compaction and land subsidence, parameter estimation, and groundwater management.

The newest version of MODFLOW (Version 6 - August 2018) provides both a Groundwater Flow Model (GFM) and a Modelling Framework. The MODFLOW 6 Framework allows developers to add both new models and interactions between the models. It provides a platform for supporting multiple models of different types within the same simulation i.e. the linking of regional scale groundwater models with a regional scale model, or the linking of surface water models with ground water models.

The GWF Model for MODFLOW 6 is based on a generalized control-volume finite-difference (CVFD) approach in which a cell can be hydraulically connected to any number of surrounding cells. The model allows you to develop a numerical representation (groundwater model) of the hydrogeological environment given defined spatial extents. Users can define the model grid using:
1.    a regular MODFLOW grid consisting of layers, rows, and columns,
2.    a layered grid defined by (x, y) vertex pairs, or
3.    a general unstructured grid based on concepts developed for MODFLOW-USG.

Conceptually the GWF Model is divided into “packages,” as was done in previous MODFLOW versions. A package is the part of the model that deals with a single aspect of simulation. Packages included with the GWF Model include those related to internal calculations of groundwater flow (discretization, initial conditions, hydraulic conductance, and storage), stress packages (constant heads, wells, recharge, rivers, general head boundaries, drains, and evapotranspiration), and advanced stress packages (streamflow routing, lakes, multi-aquifer wells, and unsaturated zone flow). An additional package is also available for moving water available in one package into the individual features of the advanced stress packages.

MODFLOW 6 is a new object-oriented program and underlying Framework was developed to provide a platform for supporting multiple models and multiple types of models within the same simulation.

Within the MODFLOW Framwork models can be independent of one another with no interaction, they can exchange information with one another, or they can be tightly coupled at the matrix level by adding them to the same numerical solution. The transfer of information between models is isolated to exchange objects in the programming, which allow models to be developed and used independently of one another.

Also within this new framework, a regional-scale groundwater model may be coupled with multiple local-scale groundwater models. Or, a surface-water flow model could be coupled to multiple groundwater flow models. The framework naturally allows for future extensions to include the simulation of solute transport.

For additional overview information see "New to MODFLOW? Start Here!" page on USGS Website.


Latest Version MODFLOW 6.0.3 released August 2018
State of Development Released and updated

Development Contact


Main Developers

  • U.S. Geological Survey (USGS)


Outcome Areas Environmental
Management Domains Freshwater
Subdomains Water Quantity/Flows, Water Quality
Intended End Users
  • Researcher
  • Regional Council Scientist
Steady State or Dynamic Unknown

Input & Output Data


Open/Closed Source Open Source

User Information

Operating Systems MS Windows
Software Needed Command Line free to download - but these codes are often then run in commercial third-party user interfaces such as Groundwater Vistas, GMS or Visual MODFLOW.
User Interface No user interface
Ease of Use Moderate
Use in Policy Process Plan (Policy Formulation), Review (Issue Identification)

Documentation for the MODFLOW 6 Groundwater flow model

Documentation for MODFLOW6 framework

Technical Considerations

Programming Language FORTRAN
Analytical Techniques Input/output
Model Structure

MODFLOW Structure

Keywords Groundwater flow, groundwater surface-water interactions, solute transport, aquifer


USGS home page of MODFLOW:

Documentation for the MODFLOW 6 framework: 

What is MODFLOW?:

Key References

Barlow, P.M., and Harbaugh, A.W., 2006, USGS Directions in MODFLOW Development (Ground Water) (80KB PDF)

Harbaugh, A.W., 2005, MODFLOW-2005, The U.S. Geological Survey modular ground-water model – the Ground-Water Flow Process (TM 6-A16)


Also see USGS Groundwater Information - Publication Page for more

Associated Case Studies

MODFLOW - West Melton Aquifer

The aim of this study was to provide background information on the groundwater system below Christchurch and its sources with a primary focus on the relationship between groundwater takes and the reliability of base flows in the Avon and Heathcote rivers.


Other Key Case Studies

Mid-Mataura Groundwater Model, Southland  (2007) Phreatos Limited. Report prepared for Environment Southland

Kaelin, N et al 2017 Evaluation of potential impacts of the Rangitata South Irrigation Scheme on groundwater Environment Canterbury Report R16/3

A simple steady state groundwater model (MODFLOW) was built to assess the effects of the Rangitata South Irrigation Scheme on groundwater levels and intermittent stream flows