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### Parameter handling

Depending on the selected models, a various amount of parameters are used to run a simulation. These parameters are sorted according to their relation (to a substance, catchment or model). GREAT-ER provides several dialogs to enter or modify the parameters.

To display the required parameters according to the selected model's complexity modes, GREAT-ER aids users with a colour coding within the dialogs: parameters colour-coded green are definitely not used by the current model selection. Nevertheless, it is possible to edit these parameters. Black parameters might be used within the current model selection.

Additionally, GREAT-ER is delivered with an expert knowledge data base on the parameters to avoid wrong data entries: Values are compared against two ranges: a warning range and an error range. The warning range specifies the usual range of a parameter. If an entry exceeds the parameter warning range, a dialog will point out this possible mistake. Nevertheless, it is possible to run a simulation with such settings. In contrast, the error range defines the logical range of a parameter. Values outside this range are impossible and will lead to errors. If a entry exceeds the error range it is not possible to leave the dialog until a value within the warning range has been entered. A dialog will give a error message and hints on the logical range of the parameter. Finally, for better documentation and transparancy of simulation results a separate comment can be entered for each parameter. This comment should mention the data source and might contain additional information on laboratory practices, etc.

Next: Starting GREAT-ER Up: Basic Concepts Previous: Model system