Mf2005.txt

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

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

NAME
     modflow - Modular three-dimensional finite-difference ground-water
               model

ABSTRACT
     MODFLOW is a three-dimensional finite-difference ground-water 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.  Harbaugh (2005) documents a general update to MODFLOW, which
     is called MODFLOW-2005 in order to distinguish it from earlier
     versions.

     MODFLOW-2005 simulates steady and nonsteady flow in an irregularly
     shaped flow system in which aquifer layers can be confined,
     unconfined, or a combination of confined and unconfined.  Flow from
     external stresses, such as flow to wells, areal recharge,
     evapotranspiration, flow to drains, and flow through river beds,
     can be simulated.  Hydraulic conductivities or transmissivities for
     any layer may differ spatially and be anisotropic (restricted to
     having the principal directions aligned with the grid axes), and the
     storage coefficient may be heterogeneous.  Specified head and
     specified flux boundaries can be simulated as can a head dependent
     flux across the model's outer boundary that allows water to be
     supplied to a boundary block in the modeled area at a rate
     proportional to the current head difference between a "source" of
     water outside the modeled area and the boundary block.

     In addition to simulating ground-water flow, the scope of
     MODFLOW-2005 has been expanded to incorporate related capabilities
     such as solute transport and ground-water management; however, this
     distribution incorporates only the ground-water flow parts of MODFLOW.


METHOD
     The ground-water flow equation is solved using the finite-difference
     approximation.  The flow region is subdivided into blocks in which
     the medium properties are assumed to be uniform.  In plan view the
     blocks are made from a grid of mutually perpendicular lines that may
     be variably spaced.  Model layers can have varying thickness.  A flow
     equation is written for each block, called a cell.  Several solvers
     are provided for solving the resulting matrix problem; the user can
     choose the best solver for the particular problem.  Flow-rate and
     cumulative-volume balances from each type of inflow and outflow are
     computed for each time step.


HISTORY

      MODFLOW-2005 Version 1.12.00 02/03/2017 -- Added Surface Water
         Routing (SWR) Package. Added FIXEDZETA option for the SWI2
         Package.  Updated the LMT Package to save flows for the
         MT3D-USGS program.  Fixed several problems in MNW2, SFR, LAK, 
         UZF, and GMG. Corrected spelling errors in source code for
         many packages.  See release.txt for a full description of changes.

      MODFLOW-2005 Version 1.11.00 08/08/2013 -- Added Seawater Intrusion
         (SWI2) Package. Added free format input option to STR Package.
         The ULSTRD list reading utility subroutine was modified to allow
         lists to be read from binary files. See release.txt for a full
         description of changes.

      MODFLOW-2005 Version 1.10.00 03/06/2013 -- Added a NOPRINT option for
         observations. Fixed several problems in MNW2, SFR, LAK, and UZF.
         See release.txt for a full description of changes.

      MODFLOW-2005 Version 1.9.01 05/01/2012 -- Fixed bug that caused MODFLOW
         to continue execution when solver closure criteria are not met and
         the percent budget error is negative.

      MODFLOW-2005 Version 1.9 03/30/2012 -- Added support for writing
         MODPATH IFACE values in the MODFLOW budget file for STR, FHB, and
         SFR Packages. Added the PCGN solver.  Many small changes
         were also made, which are documented in the release.txt file.

      MODFLOW-2005 Version 1.8 12/18/2009 -- Added MNW2 Package and made
         minor changes.  All of the changes are documented in the
         release.txt file.

      MODFLOW-2005 Version 1.7 9/23/2009 -- Added observation capability
         for the STR Package. Fixed problems with SFR, LAK, and UZF
         Packages.  All of the changes are documented in the release.txt
         file.

      MODFLOW-2005 Version 1.6.02 6/5/2009 - Fixed problem with
         multi-layer head observations in the OBS Process and computation
         of interpolated head in hydrogeologic units in the HUF Package.
         Also made other minor changes, which are documented in the
         release.txt file.

      MODFLOW-2005 Version 1.6.01 3/4/2009 - Fixed SFR problem in which
         the new NUMTIM and WEIGHT variables that are read when using
         the transient routing option (IRTFLG>0) were ignored.  Also
         added the FLWTOL input variable to SFR.

      MODFLOW-2005 Version 1.6 1/23/2009 - Added HYDMOD and LMT Packages.
         Added NOVFC option to LPF Package. Added a full double-precision
         executable version of MODFLOW for downloading (see readme.txt
         file). Also fixed several miscellaneous problems.  All of the
         changes are documented in the release.txt file.

      MODFLOW-2005 Version 1.5 4/28/2008 - Updated SFR, UZF, and LAK
         Packages to the versions used in the GSFLOW coupled ground-water
         and surface-water model. Also added the capability to use
         different damping factors in the PCG Package for transient and
         steady-state stress periods.  Added option "DDREFERENCE"
         to the Output Control Files, which was an option implemented
         in MODFLOW-2000.  Also fixed several miscellaneous problems.
         All of the changes are documented in the release.txt file.

      MODFLOW-2005 Version 1.4 11/2/2007 - Added SWT Package, added
         adaptive damping to GMG, and fixed minor problems (see
         release.txt file).

      MODFLOW-2005 Version 1.3.01 8/2/2007 - Checks added to prevent
         using HUF with UZF Package or the unsaturated flow part of
         SFR Package.

      MODFLOW-2005 Version 1.3 8/1/2007 - Fixed several minor problems
         (see release.txt file).

      MODFLOW-2005 Version 1.2.01 10/24/2006 - Fixed bug in SFR.

      MODFLOW-2005 Version 1.2 10/16/2006 - SFR, LAK, UZF, and GAG
         packages were added.

      MODFLOW-2005 Version 1.1 05/18/2006 - DRT, ETS, RES, and SUB
         packages were added.  Observations (OBS Process) as
         implemented in MODFLOW-2000 were also added.

      MODFLOW-2005 Version 1.0 01/15/2006 - Initial release.


DATA REQUIREMENTS
     In order to use MODFLOW, initial conditions, hydraulic properties,
     and stresses must be specified for every model cell in the finite-
     difference grid. Input data are read from files.


SYSTEM REQUIREMENTS
     MODFLOW-2005 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.


FUNTIONALITY
     This version of MODFLOW includes the following functionality that is
     documented in Harbaugh (2005).

         BAS -- Basic Package
         BCF -- Block-Centered Flow Package
         LPF -- Layer-Property Flow Package
         HFB -- Horizontal Flow Barrier Package
         CHD -- Time-Variant Specified-Head Option
         RIV -- River Package
         DRN -- Drain Package
         WEL -- Well Package
         GHB -- General Head Boundary Package
         RCH -- Recharge Package
         EVT -- Evapotranspiration Package
         SIP -- Strongly Implicit Procedure Package
         PCG -- Preconditioned Conjugate Gradient Package
         DE4 -- Direct solver

      The following functionality is also included. This functionality is
      documented in separate reports for use in earlier versions of MODFLOW.
      Conversion of this functionality to work with MODFLOW-2005 is
      documented in separate files that are provided with the MODFLOW-2005
      distribution.
         STR -- Streamflow-Routing Package
         FHB -- Flow and Head Boundary Package
         IBS -- Interbed Storage Package
         GMG -- Geometric MultiGrid Solver Package
         HUF -- Hydrogeologic-Unit Flow Package
         MNW1 -- Version 1 of Multi-Node Well Package
         MNW2 -- Version 2 of the Multi-Node Well Package
         ETS -- Evapotranspiration with a Segmented Function Package
         DRT -- Drains with Return Flow Package
         RES -- Reservoir Package
         SUB -- Subsidence Package
         OBS -- Observation Process
         SFR -- Streamflow-Routing Package
         LAK -- Lake Package
         UZF -- Unsaturated Zone Package
         GAG -- Gage Package
         SWT -- Subsidence and Aquifer-System Compaction Package
         LMT -- Link to the MT3DMS contaminant-transport model
         HYDMOD -- Hydrograph capability
         PCGN -- Preconditioned Conjugate Gradient solver with
                 improved nonlinear control
         SWI2 -- Seawater Intrusion Package
         SWR -- Surface Water Routing Process

Unlike MODFLOW-2000, MODFLOW-2005 does not support a parameter-estimation
process. Users of MODFLOW-2005 are encouraged to take advantage of
'clip-on' parameter-estimation programs such as PEST++. PEST++ and
supporting documentation are available at:
         http://wi.water.usgs.gov/models/pestplusplus/


DOCUMENTATION

  The basic documentation for MODFLOW-2005 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 STR Package is documented in:

Prudic, D.E., 1989, Documentation of a computer program to simulate
stream-aquifer relations using a modular, finite-difference, ground-water
flow model: U.S. Geological Survey Open-File Report 88-729, 113 p.

  The FHB Package is documented in:

Leake, S.A., and Lilly, M.R., 1997, Documentation of a computer program
(FHB1) for assignment of transient specified-flow and specified-head
boundaries in applications of the modular finite- difference ground-water
flow model (MODFLOW): U.S. Geological Survey Open-File Report 97-571, 50 p.

  The IBS Package is documented in:

Leake, S.A. and Prudic, D.E., 1991, Documentation of a computer program
to simulate aquifer-system compaction using the modular
finite-difference ground-water flow model: U.S. Geological Survey
Techniques of Water-Resources Investigations, Book 6, Chapter A2, 68 p.

  The GMG Package is documented in:

Wilson, J.D. and Naff, R.L., 2004, The U.S. Geological Survey modular
ground-water model -- GMG linear equation solver package documentation:  
U.S. Geological Survey Open-File Report 2004-1261, 47 p.

  The HUF Package is documented in:

Anderman, E.R., and Hill, M.C., 2000, MODFLOW-2000, the U.S. Geological
Survey modular ground-water model -- Documentation of the Hydrogeologic-
Unit Flow (HUF) Package: U.S. Geological Survey Open-File Report 00-342,
89 p.
     
Anderman, E.R., Kipp, K.L., Hill, M.C., Valstar, Johan, and Neupauer,
R.M., 2002, MODFLOW-2000, the U.S. Geological Survey modular ground-water
model -- Documentation of the Model-Layer Variable-Direction Horizontal
Anisotropy (LVDA) capability of the Hydrogeologic-Unit Flow (HUF) Package:
U.S. Geological Survey Open-File Report 02-409, 60 p.

Anderman, E.R., and Hill, M.C., 2003, MODFLOW-2000, the U.S. Geological
Survey modular ground-water model -- Three additions to the
Hydrogeologic-Unit Flow (HUF) Package: Alternative storage for the
uppermost active cells, Flows in hydrogeologic units, and the
Hydraulic-coductivity depth-dependence (KDEP) capability:U.S. Geological
Survey Open-File Report 03-347, 36 p.

  The MNW1 Package is documented in:

Halford, K.J. and Hanson, R.T., 2002, User guide for the drawdown-limited,
multi-node well (MNW) package for the U.S. Geological Survey's modular
three-dimensional finite-difference ground-water flow model, versions
MODFLOW-96 and MODFLOW-2000: U.S. Geological Survey Open-File Report
02-293, 33 p.

  The MNW2 Package is documented in:

Konikow, L.F., Hornberger, G.Z., Halford, K.J. and Hanson, R.T., 2009,
Revised multi-node well (MNW2) package for MODFLOW ground-water flow
model: U.S. Geological Survey Techniques and Methods 6-A30, 67 p.

  The DRT and ETS Packages are documented in:

Banta, E.R., 2000, MODFLOW-2000, the U.S. Geological Survey modular
ground-water model -- documentation of packages for simulating
evapotranspiration with a segmented function (ETS1) and drains with return
flow (DRT1): U.S. Geological Survey Open-File Report 00-466, 127 p.

  The RES Package is documented in:

Fenske, J.P., Leake, S.A., and Prudic, D.E., 1996, Documentation of a
computer program (RES1) to simulate leakage from reservoirs using the
modular finite-difference ground-water flow model (MODFLOW): U.S.
Geological Survey Open-File Report 96-364, 51 p.

  The SUB Package is documented in:

Hoffmann, Jorn, Leake, S.A., Galloway, D.L., and Wilson, A.M., 2003,
MODFLOW-2000 ground-water model -- User guide to the Subsidence and
Aquifer-System Compaction (SUB) Package: U.S. Geological Survey Open-File
Report 03-233, 46 p.

  The OBS Process is documented in:
  
Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, E.R., 2000,
MODFLOW-2000, the U.S. Geological Survey modular ground-water model --
User guide to the Observation, Sensitivity, and Parameter-Estimation
Processes and three post-processing programs: U.S. Geological Survey
Open-File Report 00-184, 209 p.

See file obs.pdf for documentation of the OBS Process in MODFLOW-2005,
including input instructions.

  The SFR Package is documented in:

Prudic, D.E., Konikow, L.F., and Banta, E.R., A new Streamflow-Routing
(SFR1) Package to simulate stream-aquifer interaction with MODFLOW-2000:
U.S. Geological Survey Open File Report 2004-1042, 95 p.

Niswonger, R.G., and Prudic, D.E., 2005, Documentation of the
Streamflow-Routing (SFR2) Package to include unsaturated flow beneath
streams -- a modification to SFR1: U.S. Geological Techniques and Methods
Book 6, Chapter A13, 47 p.

  The UZF Package is documented in:

Niswonger, R.G., Prudic, D.E., and Regan, R.S., 2006, Documentation of
the Unsaturated-Zone Flow (UZF1) Package for modeling unsaturated flow
between the land surface and the water table with MODFLOW-2005: U.S.
Geological Techniques and Methods Book 6, Chapter A19, 62 p.
  
  The LAK Package is documented in:
  
Merritt, M.L., and Konikow, L.F., 2000, Documentation of a computer
program to simulate lake-aquifer interaction using the MODFLOW ground-water
flow model and the MOC3D solute-transport model: Water-Resources
Investigations Report 00-4167, 146 p.

  The GAG Package is documented as part of the above SFR and LAK
  documentation.

  The SWT Package is documented in:
  
Leake, S.A. and Galloway, D.L., 2007, MODFLOW ground-water model -- User
guide to the Subsidence and Aquifer-System Compaction Package (SUB-WT) for
water-table aquifers: U.S. Geological Survey Techniques and Methods 6-A23,
42 p.

  The LMT Package is documented in:
  
Zheng, Chunmiao, Hill, M.C., and Hsieh, P.A., 2001, MODFLOW-2000, the U.S.
Geological Survey modular ground-water model - User guide to the LMT6
package, the linkage with MT3DMS for multi-species mass transport modeling:
U.S. Geological Survey Open-File Report 01-82, 43 p.

   HYDMOD is documented in:

Hanson, R.T. and Leake, S.A., 1999, Documentation of HYDMOD, a program for
extracting and processing time-series data from the U.S. Geological
Survey's modular three-dimensional finite-difference ground-water flow
model: U.S. Geological Survey Open-File Report 98-564, 57 p.

A separate file, hydmod7.pdf, documents the conversion for MODFLOW-2005.

   The PCGN Package is documented in:

Naff, Richard L.; Banta, Edward R., 2008, The U.S. Geological Survey Modular
Ground-Water Model - PCGN: A Preconditioned Conjugate Gradient Solver with
Improved Nonlinear Control: U.S. Geological Survey Open-File Report
2008-1331, 35 p.

   The SWI2 Package is documented in:

Bakker, M., Schaars, F., Hughes, J.D., Langevin, C.D., Dausman, A.M., 2013, 
Documentation of the seawater intrusion (SWI2) package for MODFLOW: 
U.S. Geological Survey Techniques and Methods, book 6, chap. A46, 47 p.

   The SWR Package is documented in:
Hughes, J.D., Langevin, C.D., Chartier, K.L., and White, J.T., 2012,
Documentation of the Surface-Water Routing (SWR1) Process for modeling
surface-water flow with the U.S. Geological Survey Modular Ground-Water
Model (MODFLOW-2005): U.S. Geological Survey Techniques and Methods, book 6,
chap. A40 (Version 1.0), 113 p.
Available online at http://pubs.usgs.gov/tm/6a40/


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    (703) 648-5001
    ogw_webmaster@usgs.gov

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