User's guide of Proceessing Modflow 5.0

154 Processing Modflow
in the List of Calibration Parameters (UCODE) dialog box (Fig. 3.55). The options are
grouped under four tabs described below.
< Parameters: The table gives an overview of the initial values and properties of each
estimated parameter. The meaning of each column of the table is describen below.
- Number: While editing a certain aquifer property or excitation, you have the option to
define the extent of an estimated paramter by assigning a unique parameter number to the
cells of interest. That unique parameter number corresponds to the Number here.
- Active: The value of an estimated paramter will only be adjusted if Active is checked.
Otherwise the user-specified cell value will be used for the simulation. Normally, the
total number of active parameters should not exceed 10, although PMWIN allows 150
parameters.
- Description: A text describing the estimated parameter can be entered here (optional),
for example, “Transmissivity in layer 3”. A maximum of 120 characters is allowed.
- Start-value is a parameter's initial value.
- Minimum and Maximum are the reasonable minimum and maximum values for the
parameter. The values are used solely to determine how the final optimized values of this
parameter compares to a reasonable range of values. Do not specify the “log” of log-
transformed parameters; they are calculated by the program.
- Log-transform: Check this flag to log-transform the parameter. Typically log-
transformed parameters are those for which negative values are not reasonable (for
example hydraulic conductivity).
< Prior Information:
Fig. 3.55 The List of Calibration Parameters (UCODE) dialog box
Similar to PEST, prior information can be defined in the UCODE modeling environment.
3.6.6 UCODE (Inverse Modeling)