Within Source, "Restriction Curves" are an approach to controlling water supply within a model and are used to reduce the water volumes released to users when the volume in the storage is declining. For instance, if dam water volumes drop below 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. Thus In this way a particular Restriction restriction is not lifted until there is some significant recovery in stored water volume above the volume at which the restriction was applied.
The “Restriction Curves” approach uses Restriction Levels, for example:
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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; when stored water volumes are declining and the proportion of full supply volume becomes equal to or less than 0.6, Restriction Level 0 changes to Restriction Level 1 (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 put in place if Restriction Level the day before was above the line (curve (i.e. it had a lower Level number , and a less severe restriction) and a . A "rising" Restriction Curve indicates when the associated Restriction Level will be adopted when yesterday's put in place when Restriction Level on the preceding day was below the line curve (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 (there is no less severe restriction than Level 0).
The figure above also shows that the critical values of stored water volume for changing Restriction Levels are allowed to change on a monthly basis. For example, a lower levels in a water storage might be expected to have lower levels tolerated 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.
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