A Continuous Accounting continuous accounting resource assessment system can be created in Source to replicate the Resource resource assessment system used in the Gwydir and Namoi in NSW. There are a number of defining features of a continuous accounting system which differentiate it from continuous sharing and annual allocation systems:
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- Ability to simulate more than one type of resource allocation and accounting method in the one scenario and to link one system to another;
- Ability to specify data to calculate the initial balance of the usage limit;
- Better simulation of management during dry periods including the ability to:
- Restrict allocations to high security accounts during dry periods where the required reserve cannot be met;
- Define the TOL factor as a variable depending on account balances. This allows a higher factor to be defined when balances are low, as a higher proportion of the allocations will be required to cover transmission losses; and
- Represent the rules which may reduce the required high security reserve.
System configuration
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A continuous accounting system
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A Continuous Accounting system can be added to a particular scenario in a project using the Resource Assessment Explorer (Edit » Resource Assessment...). Right click on the scenario and choose Add Continuous Accounting from the contextual menu (as shown in Figure 11 here). The The parameters to configure are described in Table 21. Note that the Resource Allocation Table defines the allocation priority when there is more than one account type. It also defines the TOL allocations for each eligible system account type.
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1. Continuous accounting (Configuration)
Table
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1. Continuous Accounting, Configuration parameters
Item Name | Description | |
|---|---|---|
Owner | Volume of water available for the Resource Assessment System system based on the ownership share of any assigned storages. Ignore for ownership off case. | |
Debit Type | Determines how water is deducted from all accounts associated with this continuous accounting system; based on either order or extractions. | |
Start of Water Year | Day-month that the water year starts for the continuous accounting system. Relevant for high security accounts as they are treated as annual accounts. The water year is also applicable to usage limits for the general security accounts. | |
No further resource assessments from this date | Day-month after which no further resource assessments should be conducted. | |
Timesteps per Assessment | Defines number of time-steps between assessments. | |
Assigned Storages Table | Lists all storage scenarios. These can be included as resources for the Resource Assessment System if required. | |
Account Type | Lists the account types available by default in a continuous accounting system. | |
Allocation Priority | Determines the order in which account types will be credited during a resource allocation.TOL Share (also known as the TOL factor) | Proportion of allocations which are to be held in reserve for the transmission and operation loss (TOL) account. You can enter either a fixed or variable value via a lookup table (click on the linked TOL value and choose Linear TOL share). This table relates the total volume in accounts for that account type to the TOL factor. It uses interpolation between entries, but does not extrapolate beyond the last one. |
TOL Minshare | Defines minimum TOL account as a proportion of unused entitlement that must be maintained. If this minimum cannot be met, temporary borrowing from the general security accounts occurs to achieve the required minshare. |
When you add a continuous accounting system, the following account types are automatically loaded:
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Accounts
The Accounts tab (Figure 122) provides a summary of the accounts which that have been added to the High Security and General Security account types. Additional water user account information is also displayed for each General and High Security Account type. system. A description of the parameters in this tab are provided in Table 32.
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122. Continuous Accounting (Accounts)
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| Note: In IQQM, No. of shares Number of shares is named Licence Volume. Additionally, the Initial balance and Previous Usage parameters are parameter is not available. |
Table
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2. Continuous Accounting, Accounts parameters
Item Name | Description |
|---|---|
WU Name | Name of the water user - additional water users can be added using Add Account (Figure 13). |
Config | A read only field showing the type of demand model defined for the water user. |
Type | A read only field displaying the account type. |
No. account | |
Account host | The host that is attached to the account. |
Account type | The type of account |
Number of Shares | Defines the entitlement of the water user in terms of number of shares in the system. |
Initial balance | Initial account balance. If you are going to use the initial account function, you need to ensure that there is sufficient water in storages to cover the total initial balances as well as the required reserves and TOL balance. If the initial balances are set too high a warning message will be generated and the results may not follow the required logic. |
Previous Usage | Indicates if previous usage data has been loaded for the Water User Account. A time series file can be used. |
Trigger Priority
The Trigger priority tab (Figure 3) shows how triggers have been prioritised in the system.
Figure 3. Continuous Accounting, Trigger Priority
Storage Loss Reserve
The storage loss reserve (Figure 114) is a volume which is required to account for expected evaporation and seepage losses from the storage. The reserve is debited from the available resource prior to making any other allocations. It may be made a function of the current storage volume or area, which can be specified using an expression. A minimum percentage of the required reserve that must be maintained can also be specified; restrictions are applied to general security accounts (or lowest priority account type) to achieve the required minimum reserve.
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The following parameters must also be specified:
- Minimum to cover storage losses - Defines the percentage of required reserve below which borrowing occurs. This parameter is not available in IQQM, so it must be set to zero; and
- Storage Loss Reserve Requirement - the reserve required to cover storage evaporation and seepage losses. Note that in IQQM, this requirement is defined through the number of months that evaporation is take into account. In some cases the storage loss is combined into the carryover reserve.
Figure 4. Continuous Accounting (Storage loss reserve)
High Security Groups
High Security Groups (Figure 125) define the reserve which is required for high security users (may also be referred to as essential supplies). The high security reserve requirement may be defined using two groups - a higher and lower priority group. In the case where only one group is required, you can delete the other by right clicking on the item and choosing Delete. Additional groups may also be added (right click on the Continuous Accounting system and choose the desired system to be added). This can be specified as a fixed value or as an expression. The latter can be used where there are rules that vary the high security reserve requirement.
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125. Continuous Accounting (High Security Group)
High Security accounts are treated as annual accounts with no carryover. In other words, at the start of a water year (as defined at the system level page), all accounts have their existing balance deleted and a new allocation is made. Allocation to high security accounts can be defined using a time series file or simulated based on whether or not the reserve requirement has been met. The Allocation Rules table allows you to define restrictions on allocations to high security accounts if the reserve requirement has not been completely met. The high security shares held by each water user is defined in Accounts. For example, if 1ML is the total reserve, and only 20% of the required high security reserve has been met, then high security accounts will only be given 0.3ML per entitlement share. Table 43 describes the parameters that must be specified.
Table
43. Continuous Accounting, High Security Groups parameters
Item Name | Description |
|---|---|
High Security Reserve Requirement | Defines the required reserve. May be an expression. |
Required Reserve Below Which Borrowing Occurs | The percentage of required reserve below which borrowing occurs from general security accounts. |
Time series allocation to accounts | If selected, the Allocation to accounts field is enabled, which allows you to define the allocation using an expression. |
Simulate Allocations to accounts | Enables the Using Account Rules table. Account allocations are automatically calculated. |
Using Account Rules | Choosing Interpolate results in the allocation rate being determined based on interpolation between the specified rows. If you choose Thresholds, HS Reserve Met in the allocation table is treated as a threshold that has to be exceeded for the allocation rate to apply. |
HS reserve met | Defines the High Security reserve balance as a percentage of the High Security Reserve requirement. |
HS Allocation | Defines the allocation to accounts per share in that High Security group. |
Generic system share
The generic system share (GSS) is used to allocate water to another resource assessment system. Water user accounts cannot be added directly to the GSS account from within the Resource Assessment Explorer. The accounts associated with the GSS are configured as part of the linked system. The GSS is credited as part of the continuous accounting allocation method and is debited when accounts in the linked Resource assessment system are debited. If an allocation is made to the GSS, this volume is distributed to users as part of the resource assessment phase of the linked system. The configuration dialog is shown in Figure 136.
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136. Continuous Accounting (Generic system share)
The following parameters must be specified for a GSS:
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In the Resource Assessment Explorer, the Expression Function Editor dialog allows you to link two resource assessment systems using the Time of Evaluation tab. Normally, fields in the expression function editor are lagged by a time-step (that is, they get their value from the last time-step to use in the current time-step). Enabling the During Resource Assessment checkbox results in the resource assessment system linked parameters being executed within the current time-step. As long as the resource assessment system appears above another resource assessment system in the hierarchical list, the values will be up-to-date in the time-step. Conversely, if one resource assessment system appears below a linked resource assessment system, its values will be lagged by a time-step.
General Security
This item (Figure 147) allows you to define accounting rules for accounts. The general security shares held by each water user is defined using the Accounts tab. The parameters that must be specified are described in Table 54. In the example shown in Figure 177, allocations have been defined to general security account should be simulated using the in-built continuous accounting functionality. There has been no restriction set on the minimum or maximum balance volumes. If, for example, there is a maximum balance of 2ML per entitlement share. This means that if a water user has an entitlement of 200 shares, their maximum account balance is 400ML. Two usage limits have been defined. The first says that no more than 1.25 ML can be used per entitlement share in any water year. The second says that no more than 3ML can be used per entitlement share in any 3 three consecutive water years. These rules replicate the conditions for the Namoi river system.
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147. Continuous Accounting (General Security)
Table
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4. Continuous Accounting, General Security parameters
Item Name | Description |
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Time series Allocation | Allows you to define a time series file of volume to be allocated per unit share at that time-step. This volume is added to user’s accounts based on their number of shares. |
Simulate Allocation | Determines the allocations to general security accounts which assess water availability. |
Maximum Balance | Defines the maximum volume of water which can be held in an account. If an allocation results in this limit being exceeded, then the excess amount is redistributed to other accounts. |
Minimum Balance | If a minimum balance is defined, then order or extractions will not be allowed if it will cause the balance to drop below the minimum specified. This is not included in IQQM. |
Usage Limits | |
Period | Time period that the limit applies to - Moving Water Year or Moving Window. |
Quantity | Specify if the limit is Per Unit Share or an Absolute quantity. To replicate IQQM, set this parameter to Per Unit Share. |
Years / Window | For a moving water year, enter the number of years the usage limit applies to. For a moving window, define the number of days that the usage limit applies to. |
Quantity setting | Usage limit over the period that is to be applied to all accounts. |