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Authors: Sorab Panday · Motomu Ibaraki · Christian D. Langevin · Richard G. Niswonger · Joseph D. Hughes
Resource type:Model Program Resource
Created:Aug 28, 2017 at 8:08 p.m.
Last updated: Aug 29, 2017 at 5:59 p.m. by YOUNGDON CHOI


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.

Subject Keywords

control volume finite difference formulation,MODFLOW,MODFLOW-USG

How to cite

Panday, S., M. Ibaraki, C. D. Langevin, R. G. Niswonger, J. D. Hughes (2017). MODFLOW_USG Model, https://water.usgs.gov/ogw/mfusg/, accessed 8/29/2017, replicated in HydroShare at: http://www.hydroshare.org/resource/da538bc6d38b407599888397e6ea6419

This resource is shared under the Creative Commons Attribution CC BY.


Sharing status:

  • Public Resource  Public
  • Sharable Resource  Shareable


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The people or organizations that created the intellectual content of the resource.

Name Organization Address Phone Author Identifiers
Sorab Panday GIS ENVIRONMENTAL 4590 MacArthur Blvd #285, Newport Beach, CA 92660 949-679-1070
Motomu Ibaraki The OHIO State University 275 Mendenhall Lab 125 South Oval Mall Columbus OH, 43210 614 292-7528
Christian D. Langevin USGS 12201 Sunrise Valley Dr Reston, VA 20192 703-648-4169
Richard G. Niswonger USGS 345 Middlefield Road Menlo Park, CA 94025 650-329-4534
Joseph D. Hughes USGS 12201 Sunrise Valley Dr Reston, VA 20192 703-648-5805
isCopiedFrom: https://water.usgs.gov/ogw/mfusg/
Content files
Computational Engine
Release Notes

Programming Language Fortran 90 with some Fortran 2003 extensions
Operating System Microsoft Windows XP or 7
Software Repository https://github.com/mwtoews/MODFLOW-USG/tree/6425740f3a5d725cf9de0f66ca63656724233957
Release Date 03/21/2014
Version 1.2
Website https://water.usgs.gov/ogw/mfusg/


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