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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

Using MFI with an Existing Dataset


MFI can work with MODFLOW files that were not originally created using MFI. To use existing MODFLOW data, the user must create an MFI name file. The name file must end with ".nam" and have a one to eight character prefix, which will be the MFI dataset name. The name file should include all files used by MODFLOW. Each line in the name file includes a file type, a file unit, and a file name. The file type is "LIST" for the listing file, "DATA" for a separate formatted file, "DATA(BINARY)" for a separate binary (unformatted) file, or the name of a primary option such as RCH. The order of entries does not matter. The "DATA(BINARY)" file type is used primarily for output files (head, drawdown, and budget). Units from 1 through 300 are allowed. The entries in the name file are read using free format, so spacing is not important as long as a comma or at least one space separates adjacent fields. An example name file is:

LIST 6 test.lst
BAS 1 test.bas
RCH 18 test.rch
OC 22 test.oc
PCG 23 test.pcg
DATA(BINARY) 50 test.hed
DATA 60 transmissivity.1
The MODFLOW input data also must adhere to two rules. First, for most parameters, a value of zero must be specifically represented with a zero character rather than using a field of all blanks. MFI will generally not interpret a blank field as a value, and the next non-blank field will be used instead. After this happens, the remaining data will be read incorrectly. Second, adjacent fields must be separated by one ore more spaces. Two fields that are not separated will typically be interpreted by MFI as a single value. As data are read, they are written to the log file; so the user can examine the log file in order to find where these errors have occurred.

MFI can also read MODPATH data that were created without MFI. In this situation, a MODPATH name file would already exist. This name file must be named with the MFI dataset name followed by ".mpn."


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