U.S. Geological Survey (USGS)                     modflow-lgr(1)

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NAME
     modflow-lgr - MODFLOW with Local Grid Refinement

ABSTRACT

     MODFLOW is a three-dimensional finite-difference groundwater
     model that was first published in 1984.  It has a modular
     structure that allows it to be easily modified to adapt the
     code for a particular application.  Many new capabilities have
     been added to the original model.  Mehl and Hill (2005) document
     an enhancement to MODFLOW, which is called Local Grid Refinement
     (LGR).  The combined code is called MODFLOW-LGR.  MODFLOW-LGR
     allows smaller parts of a larger model domain to be refined
     without refining the entire model.  Mehl and Hill (2007)
     expanded the original scope of MODFLOW-LGR to include multiple
     areas of refinement within a single model domain.  This version
     (2013) couples grids using the ghost-node method rather than the 
     shared node method


HISTORY

      MODFLOW-LGR Version 2.0 09/19/2013 - This is the initial release
	 of the ghost-node version of LGR2.  Grids are coupled at the
	 cell faces rather than at the shared nodes.  The Boundary Flow
	 and Head Package (BFH2) is also included.
	 This version is based on MODFLOW-2005 release 1.10.  

      MODFLOW-LGR Version 1.2 05/18/2010 - Added support for routing 
         of water across parent and child grids with streamflow routing
         simulated by the SFR Package.  See Mehl and Hill (2010) for 
         complete details.  Fixed a bug that prevented BFH from running
         stand-alone simulations.
         This version is based on MODFLOW-2005 release 1.8.
   
     MODFLOW-LGR Version 1.1.02 06/18/2009 - Fixed a bug that caused the 
         program to halt with a message indicating incorrect vertical 
         grid alignment when the grids were aligned correctly.
         This version is based on MODFLOW-2005 release 1.6.02.

      MODFLOW-LGR Version 1.1.1 04/15/2008 - Fixed a bug that caused
         incorrect printing of head at the location of maximum head 
         change in simulations with multiple children.

      MODFLOW-LGR Version 1.1 07/15/2007 - Added support for multiple
         non-overlapping child grids.

      MODFLOW-LGR Version 1.0 03/01/2006 - Initial release.


DATA REQUIREMENTS
     In order to use the LGR capability in MODFLOW-LGR, two model
     datasets are required.  The first dataset defines the larger
     model domain, and the second defines the smaller part to be
     refined.


SYSTEM REQUIREMENTS

     MODFLOW-LGR is written primarily in Fortran 90. Only the GMG
     solver package is written in C.  The code has been used on
     UNIX-based computers and personal computers running various
     forms of the Microsoft Windows operating system.


DOCUMENTATION

  The basic documentation for MODFLOW-2005 (on which LGR is based) is
  contained in:

Harbaugh, A.W., 2005, MODFLOW-2005, the U.S. Geological Survey modular
ground-water model -- the Ground-Water Flow Process: U.S. Geological Survey
Techniques and Methods 6-A16, variously p.

  The addition of LGR to MODFLOW-2005 is documented in:

Mehl, S.W., and Hill, M.C., 2013, MODFLOW–LGR --Documentation of ghost node local 
grid refinement (LGR2) for multiple areas and the boundary flow and head (BFH2) 
package: U.S. Geological Survey Techniques and Methods book 6, chap. A44, 43 p., 
http://pubs.usgs.gov/tm/6a44/.

Mehl, S.W. and Hill, M.C., 2005, MODFLOW-2005, the U.S. Geological Survey modular
ground-water model -- documentation of shared node local grid refinement (LGR)
and the Boundary Flow and Head (BFH) Package: U.S. Geological Survey Techniques
and Methods 6-A12, 68 p.

Mehl, S.W. and Hill, M.C., 2007, MODFLOW-2005, the U.S. Geological Survey modular
ground-water model -- documentation of the multiple-refined-areas capability of
local grid refinement (LGR) and the Boundary Flow and Head (BFH) Package: U.S.
Geological Survey Techniques and Methods 6-A21

Mehl, S.W. and Hill, M.C., 2010, MODFLOW-LGR -- Modifications to the Streamflow-
Routing Package (SFR2) to Route Streamflow through Locally Refined Grids: U.S.
Geological Survey Techniques and Methods 6-A34, 15 p.


CONTACT
    U.S. Geological Survey
    Office of Ground Water
    411 National Center
    Reston, VA 20192

    http://water.usgs.gov/ogw/