Perth
13.2 Adjustment and forfeiture of surface water allocation - urban water system

Supporting Information

This line item refers to the total forfeiture of water allocations for the major surface water storages within the Perth region that supply water to the urban water system.

All but one of the 14 surface water resources are used for urban water supply within the Perth region. The other (Helena River), primarily supplies water to the Kalgoorlie Goldfields, located outside of the Perth region boundary.

Quantification Approach

Data Source

Department of Water: Water Resource Licensing database, Water Corporation: Operational Data Storage System database.

Provided by

Department of Water.

Method

The portion of surface water allocation that has not been abstracted at the end of the 2010–11 year is forfeited. That is, there is no carryover of entitlements into next year's account.

For all but one of the 14 surface water urban supply licences within the Perth region, the licensed water management year is from 1 July to 30 June. For these licences, the forfeiture that occurs at the end of the 2010–11 year is calculated as the total annual allocation for these surface water resources minus the total allocation diversion, as shown in the following table.

The water supply licence for Dwellingup has a water management year that ends on 30 September. Therefore, the forfeiture reported for Dwellingup is calculated as the total annual allocation minus the total allocation diversion between 1 October 2009 and 30 September 2010.

Total forfeiture for all surface water resources within the Perth region is calculated in the following table.

 

Total forfeiture for surface water resources within the Perth region for the 2010–11 year

 

 

Volume (ML)

 

Licences with a water management year from 1 July to 30 June

 

 

Allocation announcement (refer to 21.2)

239,990

less

Allocation diversion (refer to 17.12)

115,569

 

Subtotal forfeiture

124,421

plus

Forfeiture for Dwellingup (reported on 30 Sept 2010)

90

 

Total forfeiture on 30 June 2011

124,511

 

Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

The uncertainty estimate was not quantified.

Comparative year

The following table presents substantive changes in the line item reported in this 2011 Account with the corresponding line item in the 2010 Account.

 

Comparative year information for line item 13.2

2011 Account line item

2010 Account line item

2011 Account volume for the 2009–10 year (ML)

2010 Account volume for the 2009–10 year (ML)

Change from the 2010 Account to the 2011 Account

13.2 Adjustment and forfeiture of surface water allocation - urban water system

26.1.2.4 Adjustment and forfeiture of allocation on regulated flows–high security, urban holder

98,885

98,885

Change in line item name and number