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Subsections

- Scenario Database
- Active and Open Scenarios

### Scenario Concept

The collection of data needed to perform a simulation is called a 'scenario'.

Scenarios can be stored and loaded and thus offer the quick retrieval of a certain situation. A unique title for each scenario assists the search of a specific one in a long list.

Additionally, scenarios form the basis of the exchange of complete simulation data sets (see Export / Import, Section 3.1.8).

A scenario consists of the following data:

1.
  Title: A unique name for the scenario.

2.
  Catchment ID: The ID (name) of the catchment (e.g. Aire). The catchment data themselves are not part of a scenario. Such data (eg. river network) are fixed and cannot be edited.

3.
  Substance: The whole substance data set is stored within a scenario. It is possible to edit and 'play around' with substance properties to see the effect of the simulation results. This should not affect the carefully collected substances of the substance database.

4.
  Release Data: Although the positions and number of discharge sites within a catchment are not editable, the attributes of the discharge sites can be modified. For this the set of attributes is stored with the scenario. In contrary to the substance database, modified data sets can not be written back to the GREAT-ER catchment database.
5.
  Modified Flag: The flag is set to true if any element of the scenario has been changed since the last save and hence the scenario is different to the scenario in the database with the same title. The flag is displayed in the scenario's view window title bar (see below).

6.
  Model Parameter: The complete model parameter data set needed by the GREAT-ER model is stored within a scenario. The reason for this is as for substance, the difference being that there is no model parameter database.

The most important data of a scenario are collected in the title bar of the corresponding view window. This makes the title, catchment ID, substance ID, modified state of scenario/substance and the simulation state permanently visible and avoids confusion when managing several open scenarios.

#### Scenario Database

A GREAT-ER installation always has only one scenario database: As mentioned in the section on installation, the basis for the GREAT-ER scenario database is a directory. All scenarios are stored in separate subdirectories under this specific GREAT-ER scenario directory. Each subdirectory contains several tables (with data editable by the user, like discharge data) and all additional settings mentioned above.

Simulation results are also stored in this directory. It is suggested to store further analysis results under this subdirectory, too. This will increase the transparancy of simulation results if all coherent data are stored in one directory structure. But please note, that in this case deleting a scenario will also affect the results derived from this scenario!

From the described scenario database structure it is clear that the exchange of scenarios with other GREAT-ER users will not work via scenario database files, but with the export/import feature.

#### Active and Open Scenarios

In GREAT-ER you can have many open scenarios, only one of which can active at one time. The name of the active scenario is shown in the ARCVIEW title bar. Scenario-related operations always are performed on the active scenario (eg. Close Scenario, Edit Data Start Simulation, etc).

The view window that corresponds to the active scenario is usually visible at the front. If a catchment has yet not been specified, the overview of Europe is visible.

The active scenario can be set by creating a new scenario, selecting a scenario from the scenario database or the bottom list of the first menu and by activating the corresponding View window.

Next: Substance Database Up: Basic Concepts Previous: Basic Concepts