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An example set of Restriction Curves is shown in the following figure as implemented in Source. The stored water volume is expressed as a proportion of the stored volume at full supply level; in the figure, when stored water volumes are declining and this value the proportion of full supply volume becomes equal to or less than 0.6, Restriction Level 0 changes to Restriction Level 1 . When (blue dotted line). Subsequently, when stored water volume rises to 0.7 or above the Restriction Level returns to 0 (solid red line). Hence, a "falling" Restriction Curve is used to indicate when the associated Restriction Level will be adopted if yesterday's Restriction Level was above the line (lower Level number, less severe restriction) and a "rising" Restriction Curve indicates when the associated Restriction Level will be adopted when yesterday's Restriction Level was below the line (higher Level number, more severe restriction). 'Rising' and 'falling' refer to the change in the stored water volume not the Restriction Level. The falling Restriction Curve for Restriction Level 0 is redundant and is not used.
The figure above also demonstrates shows that the critical values of stored water volume for changing Restriction Levels are allowed to change on a monthly basis. For example, a water storage might be expected to have lower levels at the end of a dry season because of water use through this season – and lower levels can be tolerated when an upcoming wet season is expected to provide inflows to the water storage and reduction in water demand. An
An example consistent with the restrictions above is provided in the figure below. This figure shows that the change in Restriction Level (shown on the y axis on the right) goes from Level 0 to Level 1 at 60% storage and from Level 1 to Level 2 occurs at 45% storage as storage volumes are getting lower and then returns from Level 2 to Level 1 at 55% storage and Level 1 to Level 0 at 70% storage.
The Restriction Curves approach provides a look-up table for Restriction Level that is dependent on the antecedent stored water volume conditions. When applying the Restriction Curves in a Source model the Restriction Level is used to adjust the time series demand for water supply.
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