Skip Links

USGS - science for a changing world

Open-File Report 2014–1109

Groundwater Resources Program

Prepared in cooperation with George Mason University

GRIDGEN Version 1.0: A Computer Program for Generating Unstructured Finite-Volume Grids

By Jyh-Ming Lien, Guilin Liu, and Christian D. Langevin

Thumbnail of and link to report PDF (1.93 MB)Abstract

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. 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.

First posted February 25, 2015

For additional information, contact:
Office of Groundwater
U.S.Geological Survey
411 National Center
12201 Sunrise Valley Drive
Reston, VA 20192

GRIDGEN Software -

Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge. More information about viewing, downloading, and printing report files can be found here.

Suggested citation:

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, 26 p.,

ISSN 2331-1258 (online)




Overview of the GRIDGEN Program

GRIDGEN Definition Blocks


Summary and Conclusions

References Cited

Accessibility FOIA Privacy Policies and Notices

Take Pride in America logo logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: GS Pubs Web Contact
Page Last Modified: Wednesday, 07-Dec-2016 20:06:35 EST