USGS - science for a changing world

USGS Groundwater Information

*  Home *  Monthly Highlights *  Data & Information *  Publications *  Methods & Modeling *  Selected Topics *  Programs *  About *  Contact Us

New & Noteworthy

Featured Science

Press Releases

USGS Groundwater Watch

USGS maintains a network of active wells to provide basic statistics about groundwater levels.

 [Image: USGS active water level wells location map.]

USGS in Your State

USGS Water Science Centers are located in each state.

 [Map: There is a USGS Water Science Center office in each State.] Washington Oregon California Idaho Nevada Montana Wyoming Utah Colorado Arizona New Mexico North Dakota South Dakota Nebraska Kansas Oklahoma Texas Minnesota Iowa Missouri Arkansas Louisiana Wisconsin Illinois Mississippi Michigan Indiana Ohio Kentucky Tennessee Alabama Pennsylvania West Virginia Georgia Florida Caribbean Alaska Hawaii and Pacific Islands New York Vermont New Hampshire Maine Massachusetts South Carolina North Carolina Rhode Island Virginia Connecticut New Jersey Maryland-Delaware-D.C.

Other USGS Water Science Areas

Water Software > Groundwater Software > MODFLOW and Related Programs > MODFLOW-USG

MODFLOW-USG: An Unstructured Grid Version of MODFLOW for Simulating Groundwater Flow and Tightly Coupled Processes Using a Control Volume Finite-Difference Formulation

Overview of MODFLOW-USG

[Image: Cover of software documentation report. ]

A version of MODFLOW, called MODFLOW-USG (for UnStructured Grid), was developed to support a wide variety of structured and unstructured grid types, including nested grids and grids based on prismatic triangles, rectangles, hexagons, and other cell shapes. Flexibility in grid design can be used to focus resolution along rivers and around wells, for example, or to subdiscretize individual layers to better represent hydrostratigraphic units.

MODFLOW-USG is based on an underlying control volume finite difference (CVFD) formulation in which a cell can be connected to an arbitrary number of adjacent cells. To improve accuracy of the CVFD formulation for irregular grid-cell geometries or nested grids, a generalized Ghost Node Correction (GNC) Package was developed, which uses interpolated heads in the flow calculation between adjacent connected cells.

MODFLOW-USG includes a Groundwater Flow (GWF) Process, based on the GWF Process in MODFLOW-2005, as well as a new Connected Linear Network (CLN) Process to simulate the effects of multi-node wells, karst conduits, and tile drains, for example. The CLN Process is tightly coupled with the GWF Process in that the equations from both processes are formulated into one matrix equation and solved simultaneously. This robustness results from using an unstructured grid with unstructured matrix storage and solution schemes.

MODFLOW-USG also contains an optional Newton-Raphson formulation, based on the formulation in MODFLOW-NWT, for improving solution convergence and avoiding problems with the drying and rewetting of cells. Because the existing MODFLOW solvers were developed for structured and symmetric matrices, they were replaced with a new Sparse Matrix Solver (SMS) Package developed specifically for MODFLOW-USG. The SMS Package provides several methods for resolving nonlinearities and multiple symmetric and asymmetric linear solution schemes to solve the matrix arising from the flow equations and the Newton-Raphson formulation, respectively.

MODFLOW-USG Information and Downloads


Software Downloads

Suggestion Citation for MODFLOW-USG v1.3.00

Panday, Sorab, Langevin, C.D., Niswonger, R.G., Ibaraki, Motomu, and Hughes, J.D., 2015, MODFLOW-USG version 1.3.00: An unstructured grid version of MODFLOW for simulating groundwater flow and tightly coupled processes using a control volume finite-difference formulation: U.S. Geological Survey Software Release, 01 December 2015,

Documentation of MODFLOW-USG

Panday, Sorab, Langevin, C.D., Niswonger, R.G., Ibaraki, Motomu, and Hughes, J.D., 2013, MODFLOW-USG version 1: An unstructured grid version of MODFLOW for simulating groundwater flow and tightly coupled processes using a control volume finite-difference formulation: U.S. Geological Survey Techniques and Methods, book 6, chap. A45, 66 p.

Point of Contact

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

Sorab Panday (
GSI Environmental
12801 Worldgate Drive, Suite 500
Herndon, VA 20170

Christian Langevin
U.S. Geological Survey
Office of Groundwater
411 National Center
Reston, VA 20175

Related USGS Software Resources

MODFLOW-USG users may be interested in GRIDGEN, a utility for creating layered quadtree grids for use with MODFLOW-USG

Other USGS Groundwater Software

The USGS develops groundwater RSS, 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.

Note: Some or all of this information is presented in Portable Document Format (PDF); the latest version of Adobe Reader or similar software is required to view it. Download the latest version of the free Adobe Reader from the Adobe web site. [Link exits USGS] Visit [Link exits USGS] for free tools that allow visually impaired users to read PDF files.

USGS Home Water Climate and Land Use Change Core Science Systems Ecosystems Energy and Minerals Environmental Health Natural Hazards

Accessibility FOIA Privacy Policies and Notices logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Contact the USGS Office of Groundwater
Page Last Modified: Wednesday, 10-Feb-2016 19:17:01 EST