The Head, Drawdown, and GWT panes of the MODFLOW Output Control dialog box are similar in appearance. They are used to control how the head, drawdown, and concentration data computed by MODFLOW will be printed in the main listing file or saved to an external file. The heads will be saved in a file with the extension ."fhd" if it is a formatted text file and ."bhd" if it is a binary file. The drawdowns will be save in a file with the extension ."fdn" if it is a formatted text file and ."bdn" if it is a binary file. Concentration data is saved in a binary file with the extension .conc.
The Save in external file checkbox activates the saving of heads, drawdowns, or concentrations in an external file.
The Print in listing file checkbox activates the printing of heads, drawdowns, or concentrations in the listing file.
Togther Frequency and N control when heads, drawdowns, or budget terms will be saved. For Frequency there are two choices
•First N times steps and each N'th time step thereafter
(The head, drawdown, concentration, or budget term for the last time step in the stress period is also printed or saved.)
•Last time step of each N'th stress period
(The head, drawdown, concentration, or budget term for the last stress period is also printed or saved.)
The first choice is the default for Frequency. The default for N is 1. If the defaults are used, the head, drawdown, concentration, or budget term will be printed or saved at the end of every time step. If the output files become very large, it may be convenient to change either Frequency or N or both. Typically, head, drawdown, concentration, and the budget will change most rapidly during the first few time steps of a stress period. Therefore ModelMuse is designed so that if data is being printed or saved for every stress period, it will always be printed or saved for the first N time steps so that these crucial time steps can be checked.
The External file type controls whether the heads, drawdowns, and concentrations will be saved in a text or binary file. Text files are easily read by humans and many computer programs. However, they take up more disk space and the values that are printed may have been rounded. Binary files require specialized programs to read but they take up less disk space and rounding is not an issue.
The External file format controls how the numbers in a formatted text file are printed. It is rarely necessary to use anything other than the default format. The user can consult a Fortran reference to understand the meaning of the various options. A preview of the Fortran Edit Descriptor is shown to the right of the controls for the External file format.
The Listing file format allows the user to control how heads or drawdowns are printed in the listing file. The user must choose between strip and wrap. With strip, the data are divided into strips 10 columns wide and the values in each strip are printed together. This facilitates visual inspection of the data. With wrap, the data for each row are printed together. However, only ten columns of data are printed on each line of text in the output file. The user must also choose among several predefined Fortran format specifiers. A Fortran reference may be consulted for the meanings of the Fortran format specifiers.
