README FILE FOR LMT6
[Version 6.4: 2/26/2010]


LMT6 is a package for MODFLOW-2000 that enables it to produce 
the information needed by MT3DMS for multi-species mass transport 
modeling.  The LMT6 Package is documented in the USGS Open-File 
Report 01-82 (Zheng and others, 2001), available from
http://water.usgs.gov/nrp/gwsoftware/modflow.html.  


REVISION HISTORY


Version 6.0: 05-25-2001
-----------------------
Initial release.


Version 6.1: 05-01-2002
-----------------------
This version corrects an inconsistency between the Link-MT3DMS (LMT6)
package and MT3DMS 4.0.  This inconsistency causes an I/O error when
the flow-transport link file saved by LMT6 is read by MT3DMS.  The 
problem only occurs when the STR1 package is used in the flow model, 
and when the Extended header option is specified for saving the 
flow-transport link file.


Version 6.2: 07-15-2003
-----------------------
This version adds support for 3 sink/source packages for MODFLOW-2000,
i.e., Multi-Node Well (MNW1), Segmented Evapotranspiration (ETS1), 
and Drain with Return Flow (DRT1), and is compatible with version 2
of the HUF Package. In addition, this version corrects a minor problem
that causes a steady-state flow solution to be saved as transient 
(with zero storage) when the LPF1 Package is used.


Version 6.3: 05-10-2005
-----------------------
This version fixes a linkage problem with the Multi-Node Well (MNW1) 
package.  The dimension of the WELL2 array in the MNW1 package has 
been increased to 18 to provide the most reliable means of storing 
saving the unique MNW identifier needed by MT3DMS.  Also, the WELL2 
array has been declared as double precision since 4/05/2005.  This 
change was reflected in this version of the LMT6 package (requiring 
changes to both lmt6.f and the calling statments in lmt6.inc inserted 
to the mf2k main program).  In addition, LMT6.3 supports the 
Model-Layer Variable-Direction Horizontal Anisotropy (LVDA) 
capability of the HUF2 package. 


Version 6.4: 02-26-2010
-----------------------
This version fixes a minor problem in the linkage subroutine for 
the Drain with Return Flow (DRT1) package.  This problem caused
the output information for the return flow cell to be undefined when 
the host drain's level is lower than the head in the drain cell.  
This normally would not lead to an error because for most compilers 
undefined variables are set to zero automatically.


NOTES ON THE FLOW-TRANSPORT LINK FILE


The flow-transport link file produced by MODFLOW-2000 through the 
LMT6 Package can be saved in either an unformatted (binary) file 
or an ASCII text file with free format.  The former can be read by 
all versions of MT3DMS while the latter only by MT3DMS version 4.0 
or later.  Because an ASCII text file requires much more disk space 
than an equivalent unformatted (binary) file, the ASCII text file option 
is intended mainly for debugging purposes when the unformatted (binary) 
option fails to work properly.

The structure of unformatted (binary) files used in MODFLOW-2000 is 
controlled by a number of "specifiers" in the file 'openspec.inc' 
as part of MODFLOW-2000 distribution files.  These specifiers are 
used in the OPEN statement to open the flow-transport link file along 
with other input/output files.  If non-standard specifiers are used, 
such as ACCESS = 'TRANSPARENT' or FORM = 'BINARY', it may be necessary 
to use the same OPEN statement specifiers in the MT3DMS code for the 
flow-transport link file to be read by MT3DMS correctly.  For MT3DMS 
version 4.0 or later, the structure of unformatted files is specified 
in the source file 'filespec.inc', similar to 'openspec.inc' used by 
MODFLOW-2000. For MT3DMS version 3.5 or earlier, the file opening 
function is in the subroutine OPENFL of the Utility Package.