Ownership at nodes and links

This section describes how to configure ownership at each of the nodes and links in Source.

Controlled splitter node

Ownership information is required at splitter nodes to determine the proportion of each owner’s water to be directed to each outlet (as shown in Figure 1). Ownership of unallocated flows from a splitter can be distributed according to owned amounts or by selecting different proportions to the owned amounts. The following parameters are optional:

• High flow threshold - the threshold above which high flow losses occur; and
• Don’t Borrow to Meet - if enabled, the model will attempt to get as close as possible to the specified proportions without borrowing water.

Gauge node

For the Gauge node, you must specify the sharing method (either as percentage or a unit share) and whether ownership must be reset using the Reset Ownership checkbox (Figure 2).

Figure 2. Gauge node (Ownership)

Inflow node

The Sharing Method is a volumetric entitlement for sharing water amongst owners (Figure 3) as either a proportion (by selecting Fixed Percentage) or as a function (by selecting Owner Flow Function) using the Function Editor. In the former, the proportion refers to a percentage of the total for all owners. For example, if Owner 1 is allocated 60 and Owner 2 is allocated 50, the first owner's proportion will be a percentage of the total proportions (ie.60/(60+50))%.

Figure 3. Inflow node (Ownership)

Loss node

Click the Ownership tab in the node’s feature editor (Figure 4) to choose the sharing method and specify the proportion for each owner. The High Flow Threshold checkbox refers to the threshold above which high flow losses occur, for which you can specify a threshold flow rate.

Maximum Order Constraint node

Specify the maximum order constraint via a function using the Function Editor. Also include the proportion for each constraint/owner sharing level (Figure 5).

Figure 5. Maximum Order Constraint node (Ownership)

Minimum Flow Requirement node

If there are multiple owners, the additional orders to meet minimum flow requirement (or total shortfall) are shared according to the owners' share of the minimum flow requirement.  That is, the orders for each owner will increase by their share of the Minimum Flow Requirement - Owner's Downstream Orders (or owner's shortfall).  The minimum value an owner's shortfall can be is zero, so if their share of the Minimum Flow Requirement is less than their Downstream Orders, the total owners shortfall will be less than the total shortfall.  In this case the owner's orders will be increased by the Owner's Shortfall / the Total Owners Shortfall x Total Shortfall - a larger amount.

The owner's share can be specified as Proportional (shared equally) or Fixed (enter the proportion for each owner in the Minimum Order Sharing table of Figure 6).

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.

As per the figure, 'Use Airspace' option is enabled for the owner 'Blue' . Therefore, Blue can exceed its capacity share of 40,000 ML temporarily instead of internal spilling when there is enough airspace in the storage. The owner which enables the 'Use Airspace' can increase its capacity when the non airspace owners ('Red' and 'Yellow') are not using full share of capacity and the airspace owner ( here Blue) receives inflows. In this case the owner Yellow has no initial storage and hence an airspace is available for Blue to fill above its capacity provided  inflows of Red and Yellow are below 10,000 ML. As mentioned above, the capacity increase of Blue 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. It is to be noted that the owner which uses the 'Use Airspace' functionality would be the first to spill externally. 

                                          Figure 8. Internal Spilling with 'Use Airspace' option

The proportional losses sharing method used in 'Use Airspace' functionality is based on 'Owner Working Volume Proportion' approach which is different to that of the original and default approach ('Owner Capacity Share Proportion') . Therefore, in order to use the 'Use Airspace' functionality, the user has to select the working volume method from the Edit>Scenario Options>Storages>Storage Options>Proportional losses sharing method as shown in Figure 9. 

Figure 9. Proportional losses sharing methods in Storage Options

Example

An example model is shown in the Figure 10, in which the 'Use Airspace' functionality is enabled for the owner Blue in the 'Storage 1' as in Figure 8. The total inflows, minimum flow requirement and respective shares of each owner are given in Table 1 below. The storage ownership is same as in Figure 8. 

Figure 10. Example model with 'Use Airspace' option enabled for one owner

Table 1. Node configurations 

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. 

Figure 11. The example model simulation results 

Further details and calculation methods are elaborated here. 

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 12). 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.

The Adjustment option (Figure 14) allows the user to adjust the ownership mass balance on storage nodes post timestep. This is useful because often there are decisions that move ownership about as a result of management/policy decisions based on what happened that day, and so provides the option to adjust the End of day volume.

The adjustments are done post-flow phase, with a borrow if the adjustment would otherwise cause an owned volume to be negative.

Figure 14. Storage node (Ownership, Adjustment)