User-Defined Stochastic Option

With GMS v4.0, we introduced a suite of tools for performing stochastic (Monte Carlo) MODFLOW simulations.  With version 5.0, we have enhanced these options to include several new features.  First of all, the parameters dialog has been modified to be more intuitive and user-friendly.  The parameters are now organized by column and the parameter properties are listed by row.  Second, once the sampling options are selected at the top of the dialog, the parameter values for each of the model instances are listed at the bottom of the dialog.

The Histogram button can be used to generate a frequency histogram for each parameter:

The new stochastic options also include a new sampling strategy: user-defined.  In some cases, it is useful to manually enter the parameter distributions.  For example, a user may wish to define the parameter sampling using an Excel spreadsheet and then copy in the parameter values.  When the user-defined option is selected, the bottom part of the Parameters Dialog is changed to an editable spreadsheet where a set of parameter values can be manually entered or pasted from the clipboard.  The user-defined option can also be used to set up a series of model runs in batch mode.  It is a simple and powerful way to define multiple model instances for any purpose