About Restriction Curves
Once a system is in a certain state, an action occursRestriction curves allow you to control your model's behaviour based on when it enters a certain state. For instance, if dam water supply levels volumes drop below 50%, a set of water restrictions are 60%, restrictions on water supply may be imposed for a period of time to reduce the use of a declining resource. Restrictions are usually lifted when dam water volumes exceed another dam volume higher than the volume at which the restriction was applied. In this way a particular restriction is not lifted until there is some significant recovery in stored water volume above the volume at which the restriction was applied.
Restrictions or triggers can also be used to trigger events such as releases from a certain storage, desalination supply rates or environmental flows based on salinity levels. The aim of the trigger/ restriction curves is curve is to provide generate a Restriction Level time series that tracks what level of restriction the system is in. The restriction level time series generated from a run can be used to determine performance metrics and is an important result in itself. This This Restriction Level time series can then be used to modify some other variable such as demand or inflow (desalination) as well as being a measure of the standard of service delivered. For detailed information, refer to the Source Scientific Reference Guide.
As shown in Figure 1, trigger/a restriction levels might curve might have different values depending on whether the system is rising (denotes a filling system) or falling (a falling system). The number in the legend refers to the restriction level (0 for no restrictions, 1 for restriction level 1, 2 for restriction level 2 and so on).
For detailed information, refer to the Source Scientific Reference Guide.
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Note: A set of restriction curves isRestriction curves are associated with a scenario. |
Figure 1. Restriction Curve Explorer
Creating Restriction Curves
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You can model restrictions in Source with the Restriction Curve Explorer by choosing . Right click your scenario and choose Add Restriction/Trigger Level Curve to create a new restriction curve.
Configuration
You can also create multiple restriction curves sets, each referenced by a unique auto-generated index number, named Index. The first set of restriction curves curve has an index of 0 and the next 1, etc. Each set of restriction curves can curve can be used to trigger a different type of event. For example, one set can be used for water resources restrictions, a second set for environmental flows and a third for desalination trigger levels.
Initial Level refers to the restriction level that the system starts in. This could be very important when modelling a scenario run with a short time series. For instance, if a model run started during a drought, the initial restriction level would need to be set to reflect this.
Triggers
Specify the following values in the triggers table:
- Restriction Level – what level of restrictions the model is in;
- Return value – what value to modify the system with. You can write a function in Inflow or Water User node feature editor (Function Editor menu item) to modify demand and reference the return value in the function (see below);
- Falling value – the trigger value for entering that restriction level from a lower restriction level; and
- Rising value – the trigger value for entering that restriction level from a higher restriction level.
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| Note: You must enter values The falling restriction curve for Restriction Level 0 to remove ambiguity and redundancy in curves. Also, the model cannot rise out of is redundant and is not used (there is no less severe restriction than Level 0). However, you need to enter rising values for Level 0, or the model cannot leave Restriction Level 1 and enter Level 0 unless there is a Level 0 Rising Value.. |
To delete a restriction level and its associated values (ie. a row in the Triggers table), click on the narrow grey bar to the left of the row that you wish to delete (the row will turn blue) and press Delete on your keyboard.
You can also rename or delete the restriction curve using the contextual menu.
Importing and exporting curves
Once you have designed your restriction curve you can export this as a .xml file. This curve can then be imported into a different project to ensure consistency and reduce set up time. Use the Export and Import buttons respectively.
Using Restriction Curves
To delete link a restriction curve , click on the Restriction Level (in the Triggers table) that you wish to delete and press Delete on your keyboard.
Using Restriction Curves
Once you have created a restriction curve, you to your model, you need to set up several functions and modelled variables in the Function Manager. This process is detailed in Table 1, with example functions shown that use the Restriction Curve in Figure 1.
| Create a restriction curve in the Restriction Curve Explorer as described above in Creating Restriction Curves. Ensure that the trigger values are appropriate for the variable that you want to use to modify the system. | The restriction curve in Figure 1 was created, with the trigger value being a proportion between 0 and 1, representing the amount of water present in a storage in proportion to the storage's full supply volume. |
| In Function Manager create a variable that will be used to trigger entering or leaving a restriction level. That is, it will be compared to the Rising and Falling trigger values in your Restriction Curve. | $StoreProp = $vStoreVol / $vFSV where: $vStoreVol is a modelled variable equal to the Storage Volume, and; $vFSV is a modelled variable equal to the Full Supply Volume. |