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Water Software > Groundwater Software > MODFLOW and Related Programs > GRIDGEN

GRIDGEN: program for generating unstructured finite-volume grids

Overview of GRIDGEN

GRIDGEN is a computer program for creating layered quadtree grids for use with numerical models, such as the MODFLOW-USG program for simulation of groundwater flow.

[Image: Cover of GRIDGEN documentation report. ]

The program begins by reading a three-dimensional base grid, which can have variable row and column widths and spatially variable cell top and bottom elevations. From this base grid, GRIDGEN will continuously divide into four any cell intersecting user-provided refinement features (points, lines, and polygons) until the desired level of refinement is reached. GRIDGEN will then smooth, or balance, the grid so that no two adjacent cells, including overlying and underlying cells, differ by more than a user-specified level tolerance. Once these gridding processes are completed, GRIDGEN saves a tree structure file so that the layered quadtree grid can be quickly reconstructed as needed. Once a tree structure file has been created, GRIDGEN can then be used to

(1) export the layered quadtree grid as a shapefile,
(2) export grid connectivity and cell information as ASCII text files for use with MODFLOW-USG or other numerical models, and
(3) intersect the grid with shapefiles of points, lines, or polygons, and save intersection output as ASCII text files and shapefiles.

The GRIDGEN program is demonstrated by creating a layered quadtree grid for the Biscayne aquifer in Miami-Dade County, Florida, using hydrologic features to control where refinement is added.

GRIDGEN Information and Downloads


The current release is GRIDGEN v.1.0.02 (1/6/2017).

Software Downloads

Documentation of GRIDGEN

Superseded Versions

The following versions of GRIDGEN have been superseded and are not actively supported by the USGS. The software versions below are provided online for historical reference only, and may contain outdated information or broken links.

How to Cite

This USGS software has two citations associated with it.

  1. The report citation is for the original report or article documenting the underlying theory, methods, instructions, and (or) applications at the time the initial version of the software was released. This digital object identifier (DOI) is for the report.
  2. The software release citation is for the software/code itself (now referred to by USGS as a "Software Release") and references a specific version of the code and associated release date. This DOI links to the code.

In instances where an author is citing use of this software, it would be appropriate to cite both the report documenting the code and the specific software release version that was used.

Report Citation for GRIDGEN

Lien, Jyh-Ming, Liu, Guilin, and Langevin, C.D., 2015, GRIDGEN version 1.0 -- A computer program for generating unstructured finite-volume grids: U.S. Geological Survey Open-File Report 2014-1109, 39 p.,

Software/Code Citation for GRIDGEN v1.0.02

Lien, Jyh-Ming, Liu, Guilin, and Langevin, C.D., 2017, GRIDGEN version 1.0.02 -- A computer program for generating unstructured finite-volume grids: U.S. Geological Survey Software Release, 06 January 2017,

Point of Contact

Support is provided for correcting bugs and clarification of how GRIDGEN is intended to work. Only limited assistance can be provided for applying GRIDGEN to specific problems by contacting the point of contact listed below:

Jyh-Ming Lien []
Department of Computer Science
George Mason University, MSN 4A5
Fairfax, VA, 22030, USA

Christian Langevin
U.S. Geological Survey (USGS) Office of Groundwater
411 National Center
12201 Sunrise Valley Drive
Reston, VA 20192

Other USGS Groundwater Software

The USGS develops groundwater, water-quality, surface-water, and other water-resources software for use by the USGS in fulfilling its mission. Most of this software is available online for download at no charge.

Disclaimers and Notices

This software has been approved for release by the U.S. Geological Survey (USGS). Although the software has been subjected to rigorous review, the USGS reserves the right to update the software as needed pursuant to further analysis and review. No warranty, expressed or implied, is made by the USGS or the U.S. Government as to the functionality of the software and related material nor shall the fact of release constitute any such warranty. Furthermore, the software is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use. Also refer to the USGS Water Resources Software User Rights Notice for complete use, copyright, and distribution information.

Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.

See also, USGS policy on linking to non-Federal web sites.

Software License and Purchase Information

This software is a product of the U.S. Geological Survey, which is part of the U.S. Government.


This software is freely distributed. There is no fee to download and (or) use this software.


Users do not need a license or permission from the USGS to use this software. Users can download and install as many copies of the software as they need.

Public Domain:

As a work of the United States Government, this USGS product is in the public domain within the United States. You can copy, modify, distribute, and perform the work, even for commercial purposes, all without asking permission. Additionally, USGS waives copyright and related rights in the work worldwide through CC0 1.0 Universal Public Domain Dedication ( [Link exits USGS]).

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Page Last Modified: Thursday, 05-Jan-2017 15:29:40 EST