When ownership is enabled, a river model consists of owners that have a share of the total available water (resource). A distribution system is one where owners with surplus water share their allocated percentage with owners that cannot meet their requirements. Distribution Rules define how this resource can be shared amongst owners using priority levels and ratios.

Characteristics

The following apply to distribution rules in Source:

• Ownership must be enabled prior to defining distribution rules. This creates a ‘Default Distribution’ rule (shown in Figure 78) with a priority level of 1, which can be renamed, but not deleted;
• They have global scope. In other words, they are applicable throughout Source.
• Rules can be imported and exported using the buttons shown in Figure 79;
• They specify both the recipient (priority levels) and proportion (ratios) of water the recipient will receive;
• They do not define when (time) or how fast (flow rate) the recipient will receive water; and
• Once defined, they must be applied to the relevant node.

Priority Levels

Priority levels determine the order of distribution amongst owners that require water, which occurs from highest to lowest. Surpluses must fully meet requirements (deficits) at a higher priority level before the next lower priority level is considered. In other words, they will always be executed for each owner at priority level 1, then priority level 2, and so on. Also note the following:

• The maximum number of priority levels must be one less than the number of owners. If there are 6 owners, there can only be 5 permissible priority levels; and
• If a distribution rule is operating in priority 1 and an owner cannot receive the entire distribution allocated, the rule will move onto priority 2, and so on for the lower priority levels. Consider owners A, B, C, and D, each operating at priority levels 1, 2, 3 and 4 respectively. Now, assume that A gives its spare capacity to B. However, B does not require the entire allocation. Then, A can choose to give the remainder to C, before D.

An example of a priority level description is shown in Figure 78.

Distribution Ratios

Distribution Ratios specify the proportion of surplus water that will be distributed to other owners. An owner may distribute some or all of their water to one or several owners in varying proportions. The total amount of water, including that not distributed, must at all times, remain at but never exceed 100%. Figure 81 shows the error appearing when this criterion is not met.

Configuration in Source

Choose Edit > Ownership > Distribution Rules... to open the Distribution Rules dialog shown in Figure 79. Note that the table shows the distribution ratio for each owner. Initially, this is 0% for all except the default owner (Unassigned Water), who is assigned 100%.

To add a new distribution rule:

• Right click below Default Distribution and choose Add (Figure 80);
• You can specify the distribution ratios in several ways:
• Distribute the total allocation evenly among all owners. Enable an entire row by clicking on the column left of the Execution Order. This will highlight the entire row. Click on the Evenly Between Owners tab at the bottom; or
• Manually enter the proportion that each owner will be assigned. Click on the allocation percentage for a user and enter the required amount.
• To change the number of priority levels, click on the up or down buttons next to Number of levels (Figure 79).

The rules can be viewed in two different ways using the Owner View tab and the Execution Order View tab. These are described next.

Owner View

In this tab, you can specify which owner has a surplus (using the list of owners drop down menu) and assign the distribution ratio for all the other owners. This can be done for each priority level. Figure 81 shows the surplus owner as Frank Singsalot. Priority levels 1 and 2 have equally assigned ratios among the other owners. Priority level 3 has only two owners with assigned surplus water.

Execution Order View

The tab displays the distribution rule in a different format. Each row shows the distribution ratio for all the owners, with the first column showing the surplus owner. For example, the third row in Figure 82 shows that Rita Hayless is the surplus owner, and water has been distributed evenly among the other owners. You can view this for a particular priority level.

Borrow and payback

In a distribution system, borrow records the trading of water from owners with surplus to those with deficit. On the other hand, payback occurs when the water that was lent to a particular owner is paid back to its original owner. This borrow and payback amongst users is recorded in Source in the form of the Borrow-Payback Balance (Figure 83) table, which can be accessed by choosing Edit > Ownership > Borrow-Payback Balance....

Distribution rules in nodes

You can apply distribution rules to any node where there is a loss or gain from the river. These include:

• Inflow;
• Hydraulic connector;
• Link;
• Loss;
• Supply point;
• Splitter;
• Storage; and
• Transfer ownership.

Details of using distribution rules in each of the nodes is provided in the Ownership chapter.