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Suppose one of the storage owners wants to increase its storage capacity as long there is adequate airspace to share in the storage and does not impact the actions of other owners. This can be achieved by enabling the 'Share Use Airspace' option when 'Internal Spilling' is selected as illustrated in Figure 8. In the figure, the owner 'Blue' can exceed its capacity share of 40,000 ML temporarily instead of internal spilling, when there is enough airspace in the storage. The airspace owner volume can increase while when the non airspace owners ('Red' and 'Yellow') are not using full share of capacity and the airspace owner ('Blue') receives inflows. Also, its increase should not affect the storage capacity and internal spilling of the owners 'Red' and 'Yellow'. That means if Yellow reaches its capacity and still has inflows coming in, it should internally spill to Red, given Red has available airspace. If Red still has airspace available, Blue can utilize that space to increase its share, and excess water from Blue if any will spill externally.
Figure 8. Internal Spilling with 'Share Use Airspace' option
An example model is shown in the Figure 9, in which the owners Blue and Yellow have 1000 ML/d inflows each going in to the 'Storage 1'. The Storage 1 ownership is set as in Figure 8 with Blue having the 'Share Use Airspace' enabled. All the owners (Red, Blue and Yellow) have a downstream minimum flow requirement of 100 ML/d each. The model run results are illustrated in Figure 10. It can be seen that from day 12 Yellow internally spills to Red and Blue externally spills the blue net inflow. Then on day 25 they all reach their full capacity share and from then on yellow only spills 100 to red to keep it topped up and the excess water is externally spilled.
Figure 9. Example model with 'Share Airspace' option enabled for one owner
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Figure 10. The example model simulation run results
Other ownership parameters
Lateral losses and gains include rainfall, evaporation and groundwater infiltration. These fluxes are categorised into those that are shared in proportion to the share of water stored, or according to a fixed ratio, which can be configured (as shown in Figure 11). This window is the same for Rainfall and Evaporation, and is similar for each of the Outlet Paths. An additional parameter you must specify is the distribution system that the link falls in.
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Transfer of Ownership node
At this node, the total upstream owner constraint volumes are transferred to downstream owners in specified proportions (as shown here). It can be configured as either a boundary or an in-system node. Refer to Transfer of ownership node for details.
The original downstream order can be split between the new upstream owners specified at the boundary TO node (owner proportion here), and supplied using water belonging to the specified upstream owners. When flow resulting from the released order reaches the upstream boundary of the ordering location’s ownership system, its ownership is split between downstream owners according to Flow proportions (Figure 2).
Supply Point
Ownership options at a Supply Point are illustrated in Figure 14.
The Borrow and Payback system works so that the owners' flow best matches the proportions of their orders and tracks their borrowing. Extracted volumes are restricted to the owners' flow at the supply point and their capacity to meet their downstream order. Each owners' relative shortfall is not calculated based on a proportion of the overall shortfall, but rather the individual owner's ability to meet their own orders.
The overbank sharing method is used to determine the ownership of the water taken by the supply point when the overbank threshold has been exceeded. This can be specified as a fixed ratio or proportional. The proportional overbank sharing method will take the water in the ratio of ownership currently in the river.
Figure 14. Supply Point (Ownership)
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The water user node represents a demand in the model, where orders are generated and passed upstream. Figure 15 shows the proportions distributed and returned that must be specified for each owner, when non-account sharing has been selected.
Figure 15. Water User (Ownership)
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The intention of ownership at links is to define which owner is responsible for fluxes that occur on links. This is available for lagged flow routing and storage links.
Lagged flow routing
This dialog allows you to specify what proportion of catchment inflows are allocated to each owner. Enable the Override Catchment Inflow Proportions checkbox and specify the proportion in the table below.
Figure 16. Lagged flow routing link (Ownership)
Storage routing
These fluxes are defined as a function using the Function manager. Each link’s ownership system will always match the one for the upstream connected node. You can specify what proportion of flux to allocate to each owner using the checkboxes shown in Figure 17. Once enabled, specify the proportion in the table below.
Figure 17. Storage Routing link (Ownership)
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