release.txt

                           MODFLOW-2005 Release Notes

     This file describes changes introduced into MODFLOW-2005 with each
official release; these changes may substantially affect users. In this
file, packages are referred to by their 3-or 4-character abbreviation. 
For information and references related to these packages, see mf2005.txt
("Summary of MODFLOW-2005").

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

o Version 1.11.0 08/08/2013
    GEF2SWI27 -- This is the Seawater Intrusion (SWI2) Package, which has
       been added.
    GWF2STR7 -- Added free format input option, which is used when the BAS
       Package FREE option is specified.
    UTL7 -- The ULSTRD list reading utility subroutine was modified to
         allow lists to be read from binary files.  See file the revised
         ULSTRD input instructions in file RevisedMF2005Input.pdf .
    GWF2WEL7 -- WEL Package is no longer deactivated when there are 0
       wells.
    PCGN -- Removed non-standard KIND statements.

o Version 1.10.0 03/06/2013
    OBS2BAS7, OBS2CHD7, OBS2DRN7, OBS2GHB7, OBS2RIV7, OBS2STR7 -- Added 
       NOPRINT option to turn off the output of data in the Listing File.
       See the input instructions in OBS.pdf .
    GWF2MNW27 -- a number of problems were fixed as described in
       readme_MNW2.txt .
    PCGN2 -- Corrected logic error that resulted in excessive inner
       interations in the first outer iteration of a time step.  This
       correction reduces execution time.
    GWF2BAS7 -- In the Name File for DATA and DATA(BINARY) files, the
       "OLD" option indicates that the file must already exist; however,
       the file was previously opened with the READWRITE action specifier.
       A modification has been made so that such files are opened with the
       READ action specifier, which allows other programs to read the files
       while MODFLOW is running.
    GWF2DRT7 -- Modified the open statement for OPEN/CLOSE files to
       specify that these files are opened for READ access rather than
       the defult READWRITE access.
    GWF2SFR7, GWF2LAK7, GWF2UZF1, GWF2GAG7 -- See file
       LAK_SFR_UZF_updates_MF2005.txt for a description of changes.

o Version 1.9.01 05/01/2012
    GWF2BAS7 -- Fixed bug that caused MODFLOW to incorrectly continue
       execution when solver closure criteria are not met and the
       percent budget error is negative.  The bug occurred even when the
       new STOPERROR option was not being used.
      
o Version 1.9.0 03/30/2012
    GWF2BAS7 -- Added an option, STOPERROR, to specify a budget criterion
       that allows a simulation to continue running even if the solver
       closure criteria are not met.  "STOPERROR" is an optional keyword
       that can be specified in the options list (input item 1) of the Basic
       (BAS) Package input file.  The real number, STOPER, must follow
       the keyword.  STOPER is a percent discrepancy that is compared to the
       budget percent discrepancy when the solver convergence criteria are
       not met.  Execution will continue unless the budget percent
       discrepancy is greater than STOPER. 
       Added information in the listing file about the precision of
       variables.  This shows whether the code was compiled used mixed
       double and single precision or full double precision. Increased the
       number of digits used for printing the number of time steps in
       some format statements.
       Increased the number of digits used for printing the time step from
       3 to 5 in several places.
    GWF2STR7 -- Added support for compact budget and auxiliary data.  For
       example, this allows the specification of IFACE for use with
       MODPATH.  The auxiliary data are defined as in the other packages,
       such as the RIV Package, that allow auxiliary data.
    GWF2FHB7 -- Added the functionality to write the FHB IAUX input variable
       for flow boundaries into the budget file as the MODPATH IFACE
       variable.  This happens automatically if COMPACT BUDGET AUXILIARY
       is specified in the Output Control file.
    GWF2LPF7 -- Added an option to turn off the checking that a value is 
       defined for all cells when parameters are used to define layer data.
       This option is implemented by specifying the keyword "NOPARCHECK" as
       one of the options in input Item 1 of the LPF input file.
    GWF2SFR7 --  A number of changes were made, including some new options.
       The changes, including modified input instructions, are described 
       in file LAK_SFR_UZF_updates_MF2005.txt. Input files for the prior
       release 1.8 of MODFLOW-2005 continue to work.  Consolidated SFR
       input instructions are included in file:
                    Updated_SFR2_input_instructions_MF2005.pdf .
    GWF2LAK7 -- A number of changes were made, including a new option to
       specify lake bathymetry data through external files. The changes,
       including modified input instructions, are described in file
       LAK_SFR_UZF_updates_MF2005.txt. Input files for the prior release
       1.8 of MODFLOW-2005 continue to work.
    GWF2UZF7 -- A number of changes were made, including some new options.
       The changes, including modified input instructions, are described
       in file LAK_SFR_UZF_updates_MF2005.txt. Input files for the prior
       release 1.8 of MODFLOW-2005 continue to work.
    PCGN2 -- Added the PCGN solver.
    GWF2MNW27 -- A bug was fixed that affected simulations when both MNW2
       and the HUF Package were used in the same simulation in conjunction
       with the partial penetration correction. The variable KY is now
       declared as a Double Precision variable instead of being implicitly
       assumed (incorrectly) to be an Integer variable.  A number of minor
       changes were made in Format statements to produce a cleaner output
       file.  In Subroutines GWF2MNW27BCF and GWF2MNW27HUF, corrections
       were made to assure the correct check is made for steady-state or
       transient conditions and to prevent a divide by zero error if a cell
       is dry. A bug was fixed for the calculation of angles theta and omega
       for slanted wells with an orientation into the southwest directional
       quadrant.  Fixed a bug that caused erroneous values to be written to
       the compact budget file (specifically, for inactive MNW wells),
       although the numerical solution was accurate, as were the budget
       numbers written in the main listing file.
    LMT7 -- Updated the code to support MNW2. Data handling was updated to
       support use in the Local Grid Refinement (LGR) version of MODFLOW.
       The input file is unchanged
    GWF2GHB7 -- Fixed bug that prevented NO PRINT option from working.
    OBS2BAS7 -- Fixed a problem with multi-layer head observations.
       Observations involving an interpolation to a single neighboring cell
       were incorrectly eliminated.
    GMG7 -- Fixed a problem that caused MODFLOW to abort in some rare
       conditions.
    SIP7 -- Modified SIP to avoid failure in the unusual situation that head
       change is 0 at all cells for an iteration.
    PCG7 -- Fixed a memory access error when the polnomial preconditioner
       is used. Added IHCOFADD option. When an active cell is surrounded
       by dry cells, the cell normally converts to dry.  The new option
       causes the cell to convert to dry only if storage and head-dependent
       boundary flow are also 0.  IHCOFADD is a 4th integer input item read
       on the first input line.  A non-zero value activates the option.  An
       unspecified or 0 value turns the option off.
    DE47 -- Modified code to allow a solution to occur for a single-cell
       model.
    GWF2SUB7 -- Fixed an uninitialized variable that caused MODFLOW to abort
       in some situations.
    GWF2HUF7 -- Fixed a bug that caused flow across some cell faces to be
       incorrectly saved in the budget file, which affected Modpath. Fixed
       A bug that caused an array to go out of bounds in some situations.
       Fixed a bug that caused excessive time to be spent substituting
       parameter values for arrays.

o Version 1.8.0 12/18/2009
    Added MNW2 Package.  This is an alternative to the original MNW
       Package, which is referred to as MNW1.  MNW1 remains in
       MODFLOW-2005, but both packages cannot be used in the same
       simulation.
    GWF2SFR7 -- Runoff generated by the UZF Package was not being added
       to the assigned stream reaches within the Formulate routine of the
       SFR2 Package; however, this runoff was being added to stream
       reaches within the Budget routine, which caused mass balance
       errors. The bug has been corrected.
    GWF2UZF1 -- Fixed a problem in which UZF was obtaining 0 for the
       vertical K when the top layer is inactive.  UZF will
       now obtain vertical K from the uppermost active layer.
    GWF2LAK7 -- Two minor bugs were corrected -- see readme_LAK.pdf.

o Version 1.7.0 9/23/2009
    GWF2BAS7 -- Added MXITER to the GLOBAL Module so that a different
       value can be used for each grid when using Local-Grid Refinement
       (LGR).  This change has no impact if LGR is not being used.
    Added observations from the Streamflow-Routing Package (STR) to the
       Observation Process.
    GWF2ETS7 -- Added option (NESTOP=3) to cause ET to be applied to the
       uppermost active cell in each horizontal location.
    GWF2SFR7 --  A bug was fixed that caused the model to fail to
       converge or to produce erroneous results in simulations with
       transient streamflow routing when the ICALC=3 option was used.
       Another bug was found in the calculations of mid-point flow, which
       is printed to the gage output. This erroneous streamflow
       calculation did not affect anything other than the printed
       streamflow at the mid-point of a stream reach to the gage file.
       See file readme_SFR.pdf in the doc\Updates directory for the full
       history of SFR changes and information about updated SFR input
       instructions.
    GWF2UZF1.f -- A bug was fixed that affected the value of the
       UZF input variable VKS. The error occurred if the vertical
       hydraulic conductivity for UZF was specified in the LPF input
       file and if the LPF input variable LAYVKA was not set to 0, such
       that the LPF input variable VKA is the ratio of horizontal
       to vertical hydraulic conductivity.  A bug was fixed in which UZF
       was not allowing recharge and discharge to be simulated for dry
       lake cells when the LAK Package was being used.  Another bug was
       fixed that, in some cases, caused water content profiles to be
       incorrectly printed in separate files. This bug did not affect
       simulation results.  Finally, the options for writing unsaturated
       flow budget files were changed.  See file readme_UZF.pdf in the
       doc\Updates directory for the full history of UZF changes.
    GWF2LAK7.f -- To allow the user to better assess the reliability of
       the lake calculations, time-step and cumulative mass-balance errors
       (as percent discrepancy) are calculated for each lake and have been
       added to the lake budget output information in the main listing file
       and to the gage output file for a lake.  The Lake Package was also 
       modified to always write IFACE values when saving data to a compact
       budget file. This will facilitate enhanced  compatibility and
       consistency with MODPATH.  Modifications were made to the code to
       better evaluate the lake volume and changes to lake volume for each
       time step and to allow the lake to drain and fill on the basis of
       surface water and groundwater inflows and outflows.  See file
       readme_LAK.pdf in the doc\Updates directory for the full history of
       LAK changes.
    GWF2GAG7.f -- Two new output options have been added to the Stream and
       Lake Gaging (GAGE) Package. An option has been added for Stream
       output to list selected budget components summed over all stream
       reaches when unsaturated flow is simulated (OUTTYPE = 8) and an
       option has been added for Lake output to print volumetric flow rates
       at a Lake gage (OUTTYPE = 4). See file Gage7_input_instructions.pdf
       in the doc\Updates directory for complete descriptions of the options.

o Version 1.6.02 6/5/2009
    OBS2BAS7 -- Fixed a bug that incorrectly caused some multi-layer
       head observations to be eliminated because dry cells were being
       checked in the wrong layer.
    HUF2 -- Fixed a bug that sometimes caused the interpolated head in 
       hydrogeologic units to be incorrectly calculated.
    OBS2 -- Additional digits included in the output of simulated
       equivalents.
    GWF2BAS7 -- Increased maximum number of clusters and instances for 
       defining parameters.
      
o Version 1.6.01 3/4/2009
    GWF2SFR7 -- Fixed the 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 variable, which is
       documented in the readme_SFR.txt file.
      
o Version 1.6.00 1/23/2009
   GWF2BAS7 -- Changed the message printed when the solver does not meet
       convergence criteria. Old message: "FAILED TO CONVERGE ...". New 
       message: "FAILED TO MEET SOLVER CONVERGENCE CRITERIA ...".  The
       maximum number of parameters has been increased from 999 to 2000.
   Main program -- Fixed bug that caused numerical error messages from SIP,
       PCG, and DE4 solvers to print multiple times.
   PCG7 -- Added statement to write locations of isolated cells that are
       converted to no flow.
       The code was modified to set DAMPPCG to 1.0 if the user specifies it
       as 0.0. Similarly, DAMPPCGT is set to 1.0 if the user specifies it as
       0.0 
   GWF2SWT7 and GWF2SUB7 -- Fixed the problem in which a divide-by-zero
      error occurred when these packages were used with a steady-state
      stress period with PERLEN specified as 0.0 .
   GWF2HUF7 -- Fixed bug in which error messages identifying problems
       with vertical conductance calculations specified reversed row and
       column indices.
       A bug was fixed to allow proper calculation of SC1. Previously,
       the method of computing SC1 allowed the portion of an HGU that is
       above the topmost active cell or below the bottommost active cell 
       to be included in the HGU thickness within those cells.
   GWF2SFR7 -- Added a check for values of streambed thickness that are
       zero.  Removed duplicate declaration of variables NHUF and HGUVANI.
       Added definitions of NUMTIM and WEIGHT to the readme_SFR.txt file.
   GWF2LAK7 -- Reactivated the capability to use LAK with the HUF PAckage.
   GWF2UZF1 -- Removed duplicate declaration of LAYTYP.
   GMG7 -- Fixed bug that caused a file unit error when IADAMPGMG was 1 or 2.
   Added HYDMOD -- This saves data for producing hydrographs.
   Added LMT7 -- This is the link to the MT3DMS transport code.
   OBS2BAS7 -- Fixed a bug that caused incorrect values for multi-layer
       head oservations.  Incorrect weights were being used in some
       situations.
   GWF2BCF7 -- Fixed problem in which input items 1 and 2 were read with
       free format even when fixed format was specified.
   GWF2LPF7 -- Added the NOVFC option, which turns off the vertical flow
       correction under dewatered conditions.  This option turns off the
       vertical flow calculation described on p. 5-8 of USGS Techniques
       and Methods Report 6-A16 and the vertical conductance correction
       described on p. 5-18 of that report.  To activate the NOVFC option,
       use the keyword NOVFC as the Options Variable at the end of Item 1
       in the LPF Package input file (see Options variable on pages 8-28
       and 8-29 of TM 6-A16).

o Version 1.5.00 4/28/2008
   PCG7 -- Added capability to use different damping factors for transient
       and steady-state stress periods. See readme_PCG.txt.
   GWF2LPF7, GWF2BCF7, GWF2HUF7 -- Set HNEW=HNOFLO when a cell initially
       has all transmissive terms as 0 rather than setting HNEW=888.88 .
   GWF2BAS7 --  Added variable HDRY to module GWFBASMODULE.  The LPF, BCF,
       HUF, MNW, UZF, and SFR Packages were modified to access HDRY through
       GWFBASMODULE.
       Added the ability to change the reference time step when computing
       drawdown, which was also an option in MODFLOW-2000.  This is done
       through the Output Control option. For each time step for which
       output is desired, "DDREFERENCE" can be optionally specified at the
       end of any "PERIOD n STEP n" line, and indicates that the heads
       calculated at the end of the associated stress period and time step
       are to be used as the reference heads for calculating drawdown for
       all subsequent time steps up to the next occurrence of DDREFERENCE.
       By default, the initial heads will be used for calculating drawdown.
       For example, if the user specifies the following input line:
          PERIOD 2 STEP 1 DDREFERENCE
       then heads calculated at the end of time step 1 in stress period 2
       will be used as the reference heads for calculating drawdown until
       DDREFERENCE occurs in another "PERIOD n STEP n" line.
   GWF2GAG7 -- Removed duplicate reference to variable RNF in the
       USE GWFLAKMODULE statement in SGWF2GAG7LO.
   OBS2BAS7 -- Fixed a problem where a head observation was incorrectly
       omitted when some of the neighboring cells used in the horizontal
       spatial interpolation were dry.
   GWF2SFR7FM -- Fixed precision problem that caused convergence problems
       for steady-state time steps.  Updated to the version used in GSFLOW.
       See readme_SFR.txt.
   GWF2LAK7 and GWF2UZF1 -- Updated to the version used in GSFLOW.  UZF
       has a small change in input data.  See readme_LAK.txt and
       readme_UZF.pdf.
   GWF2CHD7, GWF2GHB7, GWF2RIV7, GWF2DRN7 -- Fixed bug that caused the
       program to stop when the NOPRINT option is used with parameters.
   GWF2HUF7 -- A bug was fixed to allow proper handling of SY parameters.
       HUF was also modified to calculate vertical hydraulic conductivity
       and specific yield for all cells in the uppermost cells at the
       beginning of the simulation as required for use with UZF. See
       readme_HUF.txt.

o Version 1.4.00  11/02/2007
   Added SUB-WT Package
   GMG -- Added adaptive damping option as documented in "GMG_Damping.pdf"
       and "Banta_damping_paper.pdf" in the doc directory.
   GWF2LAK7 -- Corrected precision declaration for functions FINTERP,
       DERIVTERP, and OUTFLWTERP.

o Version 1.3.01
   GWF2BAS7 -- MXPAR, the maximum number of parameters, increased from
       500 to 999.

o Version 1.3
   GWF2GAG7 -- Removed duplicate reference to RNF in USE statement in
       subroutine SGWF2GAG7LO.  Modifications to format statements.
   GWF2UZF1 -- Fixed memory allocation problem when using UZF to simulate
       discharge to land surface while not simulating unsaturated flow.
       The calculation was changed for simulating head-dependent recharge
       and discharge when the ground-water head is near or above land
       surface.
   GWF2SFR7 -- Fixed logic for reading mixed parameter and nonparameter
       input data.
   GWF2SFR7 -- Fixed problem where FLOWC was uninitialized when ICALC=0.
       Added ability for SFR to be used with HUF.
   GWF2RCH7, GWF2EVT7, GWF2ETS7 -- Added a check to not use the layer
       indicator value if the indicator value is 0.
   OBS2BAS7 -- Changed format for saving observations in a disk file to
       write less digits..
   OBS2BAS7 -- Fixed problem with head-change observations at cells that
       have an initally dry simulated value, but values at later time are
       wet.  The later values were being computed based on the dry value,
       and now all of the values at later times will be dry.

o Version 1.2.01  10/24/2006
   GWF2SFR7 -- A bug was discovered in SFR7 when NSTRM is postive or when
       NSTRM is negative and ISFROPT is 0. The error  occurs because record
       6 is not read after the first stress period. This causes the read
       sequence following stress period 2 to be incorrect. Many different
       problems can occur due to this bug, including stopping of the model.

o Version 1.2  10/16/2006
   Added SFR, LAK, UZF, and GAG Packages
   GWF2MNW7 -- Converted PLOSS to double precision
   DE47 -- Added missing arguments in the call from MAIN to DE47AP
   KDEP capability in GWF2HUF2 -- Corrected memory allocation for GS array
          when IFKDEP is 0.
   GWF2DRT7 -- A bug that caused a budget error when a drain-return cell 
       is inactive has been fixed.  Now, if the return cell is inactive
       (IBOUND=0) or constant-head (IBOUND<0), no return flow takes place,
       and all drain flow exits the model.  Also a bug that caused an error
       reading non-parameter data was fixed.
   GWF2SUB7 -- Modified to allow comment lines to be inserted into the SUB
       input file anywhere except where arrays are to be read by one of the
       array-reader subroutines (U2DREL or U2DINT).

Note to users of the Hydraulic-Conductivity Depth-Dependence (KDEP) capability:
The memory allocation error for the GS array exists in the KDEP code
beginning with its first release in version 1.12 of MODFLOW-2000 (MF2K)
and continuing through version 1.15 of MF2K. The error was fixed beginning
with version 1.16. The error also occurs in versions 1.0 and 1.1 of
MODFLOW-2005.  The error has been found to cause problems in some (but not all)
models that specify input variable IFKDEP equal to 0. Variable IFKDEP is a flag
indicating the source of the array specifying reference-surface elevations used
for the depth-dependent hydraulic-conductivity calculations. When IFKDEP = 0,
the TOP array specified in the Discretization Package Input File is used; when
IFKDEP = 1, the array is specified in the KDEP input file (variable RS). In
some circumstances, specification of IFKDEP = 0 led to inadequate allocation
of memory for the reference surface.  The error could cause errors in some of
the budget calculations.  Models that specify IFKDEP = 1 should not be affected
by this error.  If users are uncertain whether their simulations using KDEP are
affected by this error, they are encouraged to run their data sets with MF2K
version 1.16 (or higher) or MODFLOW-2005 version 1.2 (or higher) and compare the
new results with those of the earlier version.


o Version 1.1  05/18/2006
   SGWF2LPF7DA -- Corrected deallocation statements for several variables
   hufutl7.f -- Removed some unused code
   De47.f -- Moved several variables into DE4MODULE to support Local Grid
             Refinement (LGR)
   GWF2BAS7AR -- added MFVNAM as an argument to allow different versions of
                 MODFLOW to print a different version name -- e.g. MODFLOW-LGR
                 as opposed to MODFLOW-2005.
   Added DRT, ETS, RES, and SUB packages
   Added Observation (OBS) Process
   GWF2MNW7RP -- Corrected HDRY value when HUF is used
              -- Fixed initialization problem with variable ICMN.
   GWF2MNW7 -- Added an 18th element to the WELL2 list to store a well
               identifier
   GWF2STR7 -- Increased the number of digits for output of streamflow terms
               in the Listing File.

o Version 1.00 01/15/2006:

This version is the initial release.

