[GRASSLIST:1372] Re: (no subject)

[Roger S. Miller]

On Sat, 17 Jan 1998, Rick Gagne wrote:

> >All(?) MODFLOW post-processors use its unformatted sequential access
> >output files.  The structure of FORTRAN unformatted sequential access
> >files isn't well-specified, and can differ from compiler to compiler --
> >I've run across 3 or 4 variations.  Generally MODFLOW and any program
> >that is used to postprocess MODFLOW output need to be compiled with the
> >same compiler, or a *whole* lot of work might be needed to interpret
> >from one file structure to another, and from one floating-point format
> >to another.
>
> Are work-arounds possible to allow a close mariage of MODFLOW with GRASS?

I think the commercial MODFLOW interfaces get around the problem by 1)
packaging a precompiled version of MODFLOW with their product and 2)
providing a run-time environment that controls all input and output,
including formatting.  The user really doesn't need to know much about
MODFLOW.  I think it would be possible to distribute a compiled version of
MODFLOW with a GRASS binary distribution, but I doubt that anyone is going
to write an all-encompassing software coccoon for GIS users to run MODFLOW
in GRASS.

A somewhat less intimate relationship is more realistic.  Simple interface
routines between MODFLOW and GRASS files should not be much of a problem.
MODFLOW requires two different types of input -- lists for site-specific
data and arrays for distributed data.  Lists (wells, rivers and so on) can
be stored in database tables and exported either to a MODFLOW format or to
a GRASS sites format for analysis and/or illustrations.  Distributed data
like land use, hydraulic conductivity or aquifer base elevations are again
probably best stored in a database from where it would be exported to
GRASS, processed and formatted for MODFLOW.  Note the difference; list
data would be exported from the database program to MODFLOW and
distributed data woulb be exported from GRASS to MODFLOW.  The "interface"
would consist mostly of a few programs that formatted data going into and
coming out of MODFLOW.  The user would still have to be familiar with both
GRASS and MODFLOW to make it work.


Roger Miller
Lee Wilson and Associates