The purpose of the user defined variables is to be able to identify and measure any relevant simulation quantity and to store it as a specific item into the result files. The user defined variables are defined by a mathematical expression, which can contain double numbers, analytic functions or arithmetic operations.
The 'User defined variables' table is in the User-defined-variables tree page, under 'Variable definition' page as shown in Figure 9.15.
Figure 9.15 User defined variables dialog in User Interface
To add a variable definition, click on the '+'-button, to remove a variable, click on the '-'-button. The user must specify the variable's definition, given by the following parameters:
1. Name is used for identification and as name in the result file's output item.
2. EUM type: to specify the quantity type of the result item.
3. Unit, in which the user defined variable will be stored in the result item.
4. TS Type: the time series step type with the options:
a. Instantaneous
b. Accumulated
c. Step accumulated
d. Mean Step accumulated
e. Reverse mean step accumulated.
5. Expression: the mathematical expression defines the value of the output in the result file. It can be formed by:
a. External time series: any dfs0 file with allowed EUM type and unit.
b. Sensors from the list of sensors of the basin model.
c. A large list of mathematical functions.
d. Any arithmetical operation for which no formulation error exists.
e. Connectors as logical operators for which no logical error is present.
