5.4 Inter-region commitment on surface water

Supporting Information

The volume recognised in the Statement of water assets and water liabilities represents the volume of surface water allocation remaining for water supply to the Kalgoorlie Goldfields and Agricultural region, located outside of the Perth region boundary, at the end of the 2010–11 year.

Quantification Approach

Data Source

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

Provided by

Department of Water.


Water for the Kalgoorlie Goldfields and Agricultural region is diverted from Mundaring Reservoir. The water supply licence for Mundaring Reservoir has a water management year that ends on 30 June. At the end of the water management year, any unused allocation is forfeited. Therefore, the allocation remaining on 30 June 2011 is zero, as shown in the following table.

Volume of inter-region commitment on surface water remaining at the start and end of the 2010–11 year



Volume (ML)


Opening balance (as at 30 June 2010)



21.4 Surface water allocation announcements



17.14 Surface water allocation diversion



13.4 Adjustment and forfeiture of surface water allocation



Closing balance (as at 30 June 2011)



Assumptions, Limitations, Caveats and Approximations


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 5.4

2011 Account line item

2010 Account line item

2011 Account volume at 30 June 2010 (ML)

2010 Account volume at 30 June 2010 (ML)

Change from the 2010 Account to the 2011 Account

5.4 Inter-region commitment on surface water remaining

Not applicable


Not applicable

Line item presentation: this is a new line item not reported in the 2010 Account