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- When stored water volumes are declining and the proportion of stored water to full supply volume becomes equal to or less than 0.6 for the preceding day, the Restriction Level 0 changes to the more severe Restriction Level 1 (Figure 1, blue dotted line). Hence, a Falling restriction curve lists the monthly trigger values for entering that restriction level from a lower, less severe restriction level.
- When the proportion of stored water to full supply volume rises to 0.7 or above for the preceding day the Restriction Level returns from 1 to 0 (Figure 1, solid red line). Hence, a Rising Restriction Curve lists the monthly trigger values for entering that restriction level from a higher, more severe restriction level.
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Figure 1. Example Restriction Curves
The figure above Figure 1 also shows that the Falling and Rising trigger values of proportion of stored water volume for changing for switching Restriction Levels can change on a monthly basis. For example, lower levels in a water storage might be tolerated at the end of a dry season because of water use through this season – and an upcoming wet season is expected to provide inflows to the water storage and reduction in water demand.
An example consistent with the restrictions above is provided in the figure below. This figure Figure 2, which 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 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.
Figure 2. Example model using Restriction Levels