Introduction

Many regulated river systems support several resource assessment schemes to share the available resource (water) amongst users. In Source, a resource assessment system:

is associated with only one scenario in a project, whereas a scenario may be associated with one or more resource assessment systems;
can only have one owner, but any given owner or water user may be affected by more than one system; and
supports multiple account types.

Note that resource assessment only operates correctly in a regulated system.

Figure 1 shows the various contextual menus available for each level in the resource assessment hierarchy. Note that similar types of accounts or systems have the same contextual menu. For example, all off-allocation systems have the same contextual menu, and all account types follow a similar trend.

Figure 1. Resource Assessment Explorer

In practice there are a number of resource assessment methodologies used, which can be implemented in Source using a generic resource assessment tool, referred to as Simple Water Accounting. The next section provides details on configuring two types of resource assessment in Source - general and continuous sharing.

General Resource Assessment

For detailed information about resource assessment, refer to the Source Scientific Reference Guide. To enable General Resource Assessment:

Choose Edit » Resource Assessment... from the Source main menu t open the Resource Assessment Explorer (Figure 1);
Click the disclosure triangle to the left of the scenario name and choose Add Simple System from the contextual menu.

You can edit the system name by right clicking on the name and choosing Rename from the contextual menu. Type in the field and press the carriage-return.

Once a system has been added (Figure 2), provide the following details:

Set the System Owner. There can only be one owner per system; and
Set the Water Year Start date. The system will run for 365 days from the date set.

The Accounts and Triggers tabs provide an overview of these items that have been added (generally under Account Type).

You can also assign different storages to various resource assessment systems using the Assigned Storages panel on the right. Enable the storage that you wish to add to a particular resource assessment system.

You can also configure an off-allocation system, an account type or a trigger by right-clicking the system name and choosing one from the contextual menu.

Figure 2. Simple system

Adding an account type

A system may contain several account types, each consisting of many accounts that have common properties. With resource assessment, you can group accounts according to different levels of water security, or any other common criteria appropriate to a set of accounts.

To add a new account type, click on the Accounts tab (Figure 2). Then, click Add Account Type. If desired, you can edit the account type name to be more meaningful.

Figure 2. Simple system (Account type, Configuration)

When an account type is selected, the right hand panel displays two tabs - Configuration and Accounts. The former (shown in Figure 2) is a summary of operating information for each account type. In the Allocation panel, account allocations are made using either a time series or expression. Note that allocation data is interpreted as a cumulative volume allocated per unit share. This means that accounts are only credited if there is an increase in allocation volume since the previous time-step. An account is credited by calculating the increased volume multiplied by the number of shares that the account has in the resource assessment system. The latter lists all the accounts currently configured in the system (similar to the dialog shown in Figure number). The parameters in the Accounts table are explained in Table 3.

Adding an account

In the Resource Assessment Explorer window (shown in Figure 3), right-click on the Account Type in the left hand panel and choose Add Account from the contextual menu. This is applicable to all dialogs in the Resource Assessment Explorer where you can add or delete accounts.

You can configure the properties of an account using the panel displayed in Figure 3. Note that:

Each account can have only one water user associated with it;
You must enter the number of shares that the account has in the resource assessment system; and
You can specify an opening account balance.

Figure 3. Simple system (Account type, Add new account)

Usage limits

You can limit water usage for all accounts by absolute volume or a per-unit-share, which can cover a water year or movable time window (shown in Figure7). You can define any number of usage limits.

To add a usage limit, right click on Account Type and choose Add Usage Limit;
To delete a usage limit, right click on it, and choose Delete; and
You can also rename it using the contextual menu.

Note: The usage limit, regardless of its position in the hierarchy, requires the same parameters to be configured. Figure 4 is therefore the same for all invocations of usage limit.

Figure 4. Simple system (Account type, Usage limit)

Account type triggers

A trigger initiates or cancels certain actions for an account type and can be configured using the panel shown in Figure 5. To set up a trigger, right-click the account type on the left hand panel and choose Add trigger.

Triggers can be set to activate on a particular date, a year start or end or the passing (either raising or falling) through a specified storage water level. When a trigger is activated it will initiate a pre-defined action, which is defined in the panel on the right hand side of the Triggers window. Possible actions include:

Transferring a percentage of water to another account;
Levelling accounts;
Writing off accounts; and
Truncating or assigning accounts.

An account type can have several triggers, each designed to initiate a particular action.

Figure 5. Simple system (Account type, Trigger)

Continuous Sharing Resource Assessment

A Continuous Sharing Resource Assessment System is one in which the behaviour of a water user has as little effect as possible on other water users within that system. For detailed information about continuous sharing resource assessment, refer to the Source Scientific Reference Guide. To enable it in Source:

Choose Edit » Resource Assessment...;
Click + to the left of the project name (Figure 1) to reveal the project’s active scenarios; and
Right-click the scenario for which you wish to enable resource assessment and choose Add Continuous Sharing from the contextual menu (Figure 1).

You can rename the system using the same method for simple resource assessment systems. Refer to General Resource Assessment.

System Configuration

To configure a continuous sharing system, start by selecting the owner whose share is described by this system from the Owner pop-up menu (Figure 6) and define the start of the owner’s water year. The owner may be any one of the defined owners in the physical system being modelled. The other owners are assumed to use separate allocation systems, with all calculations occurring independently.

Figure 6. Continuous sharing, Configuration

The sharing of various system losses is based on long term averages. Over time, discrepancies will emerge which must be reconciled. You can control the frequency with which reconciliations occur using the Timesteps per Reconciliation field. The default is one time-step. Shortfalls identified during a reconciliation are treated as storage losses, gains as inflows. Losses and gains are shared based on account share sizes, but ignore account priorities.

The reconciliation process also resolves situations such as when multiple resource assessment systems draw upon the same water (whether such a configuration is accidental or deliberate).

The second step is to specify the percentage shares that the owner has in each storage known to the system. You use the Owner Shares tab in the relevant storage node feature editors to accomplish this.

Next, select each storage that should participate in the continuous sharing system in the Unassigned Storages list and move it into the Assigned Storages list by clicking the button with the right arrow. Note that a storage can be removed from the Assigned Storages list by selecting the storage and clicking the button with the left arrow.

As each storage is added to the Assigned Storages list, the owner’s share in that storage is added to the Total Conceptual Storage field, which is the sum of the active capacity for this owner of all of the assigned storages in the resource allocation system. You can not edit this value directly.

By default, 100% of all allocations are considered to be high priority but you can designate a lesser proportion by adjusting the High Priority Allocation field. The related fields of High Priority Storage, Medium Priority Allocation and Medium Priority Storage adjust dynamically in response.

You can adjust the Medium Priority Threshold field to determine how inflows are assigned to accounts. The field behaves as follows:

When storage is below the stipulated threshold, inflows are only assigned to high priority accounts; and
When storage is at or above the stipulated level, inflows are assigned to both high priority and medium priority accounts according to the percentages entered in the respective priority allocation fields.

The default Medium Priority Threshold is zero, which means that inflows will be assigned to both high priority and medium priority accounts.

The System Cap Balance Carryover specifies the maximum proportion of the owner’s annual resource cap that the system can carry over into the next water year.

Finally, you can define the loss characteristics of each storage in millimetres per day between one or more start- and end-date pairs within the water year. You can also import loss characteristics from a .CSV file formatted as shown in Table 1.

Table 1. Continuous Sharing (Storage loss rate, data file format)

Row	Column (comma-separated)
Row	1	2	3
1	Loss Rate (mm/d)	Start Date	End Date
2..n	flux	start	end

Where: flux is the loss in millimetres per day for the recurrent period defined by start through end

start is the first day of each year represented as dd-mmm (eg "01-Jan") on which flux begins

end is the last day of each year represented as dd-mmm (eg "01-Jan") when flux ends.

Adding Accounts

To add accounts to a continuous sharing resource assessment system, switch to the Accounts tab (Figure 7) and click Add Accounts to open the Add Accounts dialog (Figure 8). The nodes which appear in the list on the left hand side of Figure 7 are Water User nodes, otherwise known collectively as demand nodes. Select one of the nodes in this list and click OK.

Figure 7. Continuous sharing, Accounts

Figure 8. Continuous sharing (Add accounts)

To add accounts for more than one demand node to a resource assessment system, repeat the process of clicking Add Accounts, selecting the relevant demand node, and clicking OK.

By default, an account of each type (ie. a high priority and medium priority allocation account) is added for each water user, although only one account is required to have a maximum account balance greater than zero. Note that, where the High Priority Allocation is 100% (Figure 9), the medium priority account will remain unused.

You can delete an account-pair by selecting either of its members and clicking Delete Accounts.

Account configuration

You can configure individual accounts by manipulating the controls shown in Figure 10. Fields that are grey can not be adjusted. They fall into three categories:

Values that are inherited from previous steps and which are included for reference. Examples include the Name, Type and Priority fields;
Values that are set by reference to other values. The Maximum Balance column is an example; or
Fields that must first be enabled explicitly. For example, you must enable the relevant Spec Cap checkbox before you can specify an Annual Cap.

You can allocate shares water by shares or volume. You can specify a maximum cap for an account by enabling the Spec Cap check-box and entering a volumetric limit (ML) in the Annual Cap field. This cap will limit the annual volume diverted by the associated water user.

The share factor (Share Fact) defines the relationship between orders and the amount that must be released in response to those orders, having regard to losses and gains during transmission:

A share factor in the range 0.0 < Share Fact < 1.0 indicates that a loss is expected to occur between the storage and supply point. The closer to zero, the greater the loss;
A share factor of 1.0 indicates perfect transmission between the storage and supply point;
A share factor greater than 1.0 indicates gains are expected to occur during transmission, such as inflows from a tributary;
To account for the transmission losses and gains, the volume of water released from a storage to meet a water user’s order is calculated as the Order divided by the Share Fact; and
Accounts with a lower share factor are allocated a larger share of the storage to account for the transmission losses they incur.

All share factors at a given priority level within a continuous sharing system are interrelated as follows:

Continuous Accounting

A Continuous Accounting resource assessment system can be created in Source to replicate the 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:

Assessments of whether a new allocation can be made occur intermittently (based on triggers defined within the plan) with a new allocation resulting in an additional volume of water added to user’s accounts. With continuous accounting, there is no end of year forfeiture of allocation. There are, however, limits on the volume that can be held in a general security account at any one time and usage limits may also apply;
An account is maintained for the system as a whole to meet transmission and operation losses (TOL) for delivery of regulated water. An accounting process is followed to determine whether any of the available storage volume is unallocated. The unallocated volume remains after the following have been deducted from the active storage volume:
- reserve required for storage losses;
- reserve required for high security uses including an allowance for transmission losses to deliver these supplies;
- existing volume allocated to the generic system share/s;
- existing volumes allocated to general security entitlements in this system; and
- the volume required to be held in the system’s transmission and operation loss account.
High security accounts are assigned an allocation based on a defined relationship between percentage of the high security reserve met and allocation to accounts. The reserve set aside for high security uses is generally greater than the volume that is allocated to the high security accounts. Whilst the full reserve volume is set aside at each resource assessment prior to making an additional allocation, the accounts are only assigned an allocation on an annual basis.

The enhancements to continuous accounting in Source over IQQM are:

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.

Adding a continuous accounting system

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 (Figure 9). The parameters to configure are described in Table 2. 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.

Figure 9. Continuous accounting (Configuration)

Table 2. Continuous Accounting, Configuration parameters

Item Name	Description
Owner	Volume of water available for the Resource Assessment 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. Note that for High Security accounts, the required TOL is debited from the High Security reserve as it is assumed that the defined reserve includes provision for delivery losses (as per plan requirements for the Namoi and Gwydir).
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:

Storage Loss Reserve - define the reserve required for evaporation and seepage losses from storage;
High Security Group 1 - define the reserve required for high security users. Also allows you to define accounts which relate to this reserve and the method for allocating water to these accounts;
High Security Group 2 - same as for High Security Group 1 but relates to a separate, lower priority group of high security users;
Generic System Share 1 - used to allocate water to another Resource assessment system; and
General Security 1 - allows you to define accounting rules and shares for general security accounts.

Note: IQQM includes a number of inbuilt triggers which are not replicated in Source. For this reason, the Timesteps per assessment parameter may need to be set to 1. Additionally, to replicate IQQM, the TOL Share parameter on the high security account type should be zero.

Accounts

The Accounts tab (Figure 10) provides a summary of accounts which 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. A description of the parameters in this tab are provided in Table 3.

Figure 10. Continuous Accounting (Accounts)

Note: In IQQM, No. of shares is named Licence Volume. Additionally, the Initial balance and Previous Usage parameters are not available.

Table 3. 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. 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.

Storage Loss Reserve

The storage loss reserve (Figure 11) 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.

Figure 11. Continuous Accounting (Storage loss reserve)

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.

High Security Groups

High Security Groups (Figure 12) 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.

Figure 12. 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 4 describes the parameters that must be specified.

Table 4. 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. For example, a time series file of observed allocations to High Security accounts can be loaded. The time series file is read as a volume per share to be added to accounts at that time-step.
Simulate Allocations to accounts	Enables the Using Account Rules table. Account allocations are automatically calculated. Note that the allocation to the reserve is always simulated regardless of whether this is selected or not.
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 13.

Figure 13. Continuous Accounting (Generic system share)

The following parameters must be specified for a GSS:

Time Series Allocation - Enables the entry of a time series file for allocating to the GSS;
Simulate Allocation - Define an expression to allocate to GSS. The value of the expression is treated as a volume to be added to the GSS account subject to available water limitations; and
Total Volume Initial Balance - Initial balance in the GSS account.

GSS is generally used with resource assessment system linking to an annual accounting system where a portion of the resource assessment system is determined by the output of another system.

In the Resource Assessment Explorer, the Expression Editor dialog allows you to link two resource assessment systems using the Time of Evaluation tab. Normally, fields in the expression 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 14) 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 5. In the example shown in Figure 17, 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 consecutive water years. These rules replicate the conditions for the Namoi river system.

Figure 14. Continuous Accounting (General Security)

Table 5. Continuous Accounting, General Security parameters

Item Name	Description
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. Choose **Per Unit Share** to define the maximum balance as a volume per share. In IQQM, it is referred to as maximum proportion of entitlement that can be in storage.
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. If a usage limits relates to a single water year, choose Moving Water Year* and Years set to 1. Where a "rolling years" usage limit has been defined in IQQM for general security accounts, these should be defined as *Moving Water Year* limits in Source.
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.

Ownership and resource assessment

Resource assessment systems are generally used with ownership when one owner has borrowed from a second owner, and payback is required. One method of paying back water can be accomplished through a resource assessment system. Refer to Borrow and Payback Systems, Distribution Systems for further details on configuring this arrangement in Source.

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