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A Data Input Program (MFI) for the U.S. Geological Survey Modular Finite-Difference Ground-Water Flow Model
U.S. Geological Survey Water-Resources Investigations Report 94-468


MODFLOW uses preconnected files, which means that the method of specifying the file names that correspond to Fortran's numeric file units is determined by the computer vendor. On the Data General workstations on which MFI was developed, it is required that preconnected files be named "fort.n" where n is the unit number. Thus, prior to running MODFLOW, the "fort.n" files must be created from the actual data files that are specified within MFI. MFI does this by writing a Unix shell program that creates the files, executes MODFLOW, and then deletes the "fort.n" files. The shell program is the dataset name followed by ".sh". Thus, once all data are entered and MFI is exited, MODFLOW can be run by running the shell program. Modifications to MFI may be necessary in order to meet the requirements for preconnected files on other computers. The Program Documentation Section gives information about where the modifications would be made.

MODPATH obtains information about the files that it will use from the MODPATH name file. MFI creates the MODPATH name file, and its name is the dataset name followed by ".mpn".

Although MFI creates datasets of the proper form for MODFLOW and MODPATH, it is possible for incorrect data to be entered using MFI. MFI does a lot of data checking in order to reduce the chance for errors, but the checking is not exhaustive. Further, no amount of checking can detect data entry errors in which a reasonable, but incorrect, value is mistakenly entered. Some errors will cause MODFLOW or MODPATH to stop before completion while others will result in what might first appear to be normal execution, but the results are wrong. Thus, the output files from MODFLOW and MODPATH should always be examined to make sure that data have been defined as intended.

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