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In any time-step, the water user’s demand model generates a future minimum requirement and a future ‘opportunistic’ requirement. The water user’s demand delivery component makes orders for the minimum requirement and off-allocation requests for the opportunistic requirement. It also generates a minimum and opportunistic requirement for the current time-step, and these amounts may differ from those predicted earlier. The modeller specifies the rules as to how these demands are to be distributed when they are configuring the model.
Resource assessment systems (RAS) may be used to manage sources of water (both from the river and groundwater). Every RAS is associated with a water owner. In a scenario with no ownership specified, all RAS uses the ‘not specified’ owner. RAS can manage both regulated and unregulated water sources. A regulated RAS always manages off-allocation water via off-allocation account types.
Where one or more RASs is configured for the modelling scenario, the water user node can be configured to associate a supply point’s orders and extractions with one or more resource allocation accounts, known as ‘Account Sharing’. When this type of demand distribution is used, the modeller specifies the priority of accounts to be used, via the RAS or directly at the water user node. Accounts (and hence demand) are associated with an owner via the RAS. The volume of orders and off allocation requests that can be made at the supply point in any time-step is limited by the balances of its accounts at that time-step. A supply point may be associated with multiple accounts but at most one off-allocation ‘account’ per owner.
The other method of demand distribution is ‘Non-Account Sharing’. When this is selected, the water user’s demand is distributed to each owner at each connected supply point node either (a) on a proportional basis, or (b) using fixed proportions specified for each owner by the modeller.
Distribution Loss
Some water may be lost during delivery from extraction site to water user. Distribution loss can be modeled either as an absolute component or a percentage of supplied demand (not extracted volume at extraction site, but extracted volume minus loss). Therefore, total extracted volume = absolute loss component + proportion loss of supplied demand + supplied demand = absolute loss component + (1+proportion loss) * supplied demand
Note: Distribution loss will only be taken into account in resource assessment if "Usage from Account Host plus Distribution Losses" is selected in resource assessment system.
Order supply path
The account or owner will determine the water source and delivery path used for the order at the supply point.
- Account sharing water users: Orders can be provided from any storage associated with the ordering account’s RAS. The order system determines where to source water from according to storage levels and other constraints at each time-step during the model run. Off allocation requests are always supplied from the off-allocation sharing (OAS) nodes associated with the supply point’s off-allocation accounts (if it has any).
- Non-account sharing water users: Any storage the ordering owner has a share of water and outlet capacity in can supply orders.
When there are multiple supply path options, the water ordering system determines where to source water from according to storage levels and other constraints at each time-step during the model run. For more information on how the water ordering system directs orders to storages:
- Refer to Rules Based Ordering; or
- Refer to NetLP - SRG for this type of ordering.
Updating Account balance for Water 'Use'
When account sharing is used at a water user node, the node has accounts that are debited for water ‘usage’. This usage may be for water extraction or delivery at its supply point(s), depending on whether the use is extractive or not. The timing of debiting an account and the amount debited depends on whether its RAS type is ‘order debit’ or ‘use debit’, and on whether the associated supply point is extractive or not. Note that a groundwater or unregulated river supply point must be extractive and, if it is associated with an account, the account is use-debit.
The method of account balance update is outlined in Table 26 below.
Table 3. Updating account balances at supply points
| Supply point type | Account category | Account updates |
|---|---|---|
| Extractive | Order-debit | Account is debited for the volume of the associated ‘release’ from the nearest supply source (in terms of delivery time). This is done in the order phase of the time step in which the order is placed. If some of the flow ordered is not delivered, the account is refunded as the excess order is considered to be an operating error. |
Off allocation | Account is debited for the volume of off-allocation water extracted. | |
Use-debit | Account is debited for the volume of extraction for ‘regulated use’ for which orders have been placed using use-debit accounts. This excludes the use of overbank and off-allocation water to meet use-debit requirements. | |
| In-stream | All | The modeller can specify the total amount to deduct from all the supply point’s accounts and the timing of the deduction via a function. The default behaviour (when no function defined) will be as per extractive supply points - but the ‘extraction’ in this case is the part of the current requirement assigned to the account. |
The rationale for allowing the modeller to define an expression for account debiting at in-stream supply points is that these have differing applications. In-stream supply points can be used to place orders to ensure flow for a downstream location, such as a wetland, so account debiting should not necessarily occur at the time the flow arrives at the supply point but perhaps instead when the water arrives at the downstream location. There may also be variations to how accounts are debited - e.g.,. in the case of bulk water entitlements.
Input data
Details on data are provided in the Source User Guide for the Supply point node and in the ownership section Ownership at nodes and links.
Output data
Output may be displayed in the form of graphs, tables and statistics for the variables listed in Table 6.
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