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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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