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Figure 6. Minimum Flow Requirement node (Ownership)
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|---|---|---|---|---|
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Each owner’s share of water is conserved at a storage node where ownership has been enabled except when:
- Water is ceded to other owners according to distribution rules;
- An owner does not have sufficient storage capacity to hold their water, so it is internally spilled to other owners. This can be disabled if required using the Internal Spilling radio button. Internal spilling occurs when an owner’s volume of water in storage exceeds their current storage capacity and excess is transferred to another owner.
- Water is borrowed or lent to other owners so that demand can be met, which can be later paid back either at the same storage, at the nominated payback storage, or handled by the resource assessment process.
An owner’s volume of water in storage is adjusted for their share of inflows, regulated releases, external and internal spills, lateral losses and gains, and flows along wetland links. Inflows may be from upstream or wetland links. Regulated release ownership is determined by each owner’s downstream order.
Using Figure 7, you can choose which owner will be assigned 100% ownership of the storage, its inflows, losses/gains and releases when ownership is suspended using the Override Owner drop-down menu. When conditions in the specified function are met, the ownership system will be suspended. You must also specify each owner’s share of the storage capacity, as well as the initial share.
Figure 7. Storage node (Ownership)
'Use Airspace' - Temporary increase in storage capacity for owners
Suppose one of the storage owners wants to increase its storage capacity/ownership as long there is adequate airspace in the storage and does not impact the actions of other owners. By this way the storage capacity can be fully utilised. This can be achieved by enabling the newly created 'Use Airspace' functionality when 'Internal Spilling' is selected as illustrated in Figure 8.
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Table 1. Node configurations
| Node | Total (ML/d) | Red (%) | Blue (%) | Yellow (%) |
|---|---|---|---|---|
| Inflow | 1000 | 60 | 20 | 20 |
| Minimum Flow Requirement | 500 | 50 | 10 | 40 |
The model simulation yielded the following results (Figure 11) for each owner in terms of storage volume, internal and external spills when 'Use Airspace' is enabled for the owner Blue. Though the capacity share of Blue is 40,000 ML, its capacity increases to 40150 ML on the first time step due to the availability of airspace (as Yellow is not yet full). Meanwhile, as Red already reaches its full capacity on 1/01/2022, it passes 250 ML (out of 600 ML inflow) to its downstream demand the remaining (350 ML) is internally spilled to Yellow. This keeps on occurring until 21/01/2022, when there is no airspace left and that is when Blue starts external spilling to allow Yellow to attain its capacity share. It can be seen that when Blue uses the 'Use Airspace' option, it does not spill internally and the internal spills are occurring only between non-use airspace owners.
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