Sydney
13.2 Adjustment and forfeiture of surface water allocation – urban water system

This line item refers to the the total adjustment made on surface water allocations for the urban water system for the 2012–13 year. The volume is the difference between calculated volumetric allocation stated in line item 21.2 Surface water allocation announcements – urban water system (1,040,588 ML) and regulated diversions stated in line item 17.12 Surface water allocation diversion – urban water system (542,715 ML).

The volume recognised in the water accounting statements of 497,873 ML represents the adjustment made by the National Water Account to reconcile the water accounting statements, it does not represent an actual forfeiture of the licensed allocation by individual license holders at the end of the water year on 30 June.

Water Sharing Plan for the Greater Metropolitan Unregulated River Water Sources; entitlement and diversion data recorded in databases and water management licences by New South Wales Office of Water; diversion data recorded in mass balance spreadsheets by Sydney Catchment Authority and databases by Goulburn Mulwaree Council, Lithgow City Council, and Wingecarribee Shire Council.

The Bureau of Meteorology calculated adjustment and forfeiture of allocation/claim; entitlement and diversion information provided by the New South Wales Office of Water, Goulburn Mulwaree Council, Lithgow City Council, Shoalhaven City Council, and Wingecarribee Shire Council.

Under the water sharing plan, carry-over of any unused allocation at the end of the year is allowed for licences not issued under the 'major utility' category. The maximum volume of carry-over allowed is determined by the rules in the water sharing plan and the volume of water diverted under the licence. The carry-over volume for the licences reported under this line item have not been quantified. Therefore, for the purposes of the National Water Account, the carry-over volume (opening and closing balance as reported in line item 5.2 Surface water allocation remaining) was assumed to be zero. In order to the balance the account, the liability decrease reported in this line item is equal to any remaining unused allocation.

Calculation methods for the announced allocation and measured diversions are available in:

• 21.2 Surface water allocation announcements – urban water system for the volumetric value for the announced allocation
• 17.12 Surface water allocation diversion – urban water system for metered diversions from storages.

• Carry-over has not been quantified
• Liability decrease is assumed to be equal to the remaining unused allocation at 30 June.

For entitlements: the allocation/claim was derived from the Water Sharing Plan for the Greater Metropolitan Unregulated River Water Sources. Uncertainty was not quantified.

Wingecarribee Shire Council: the volume is based on measured data. Estimated accuracy based on meter accuracy is +/– 7%. External flow verification audits for the flow meters are conducted annually by Hydrometric Consulting Services.

Sydney Catchment Authority: the volume is based on measured data. Estimated accuracy based on meter accuracy is  +/– 2%.

Lithgow City Council: the volume is based on measured data. Estimated uncertainty based on meter accuracy is   +/– 2%. Meters are calibrated annually by ABB (meter supplier).

Goulburn Mulwaree Council: the volume is based on metered data. Estimated accuracy based on meter accuracy and professional judgment is +/– 20%.

Sydney Water Corporation: the volume is based on measured data. Estimated accuracy based on meter accuracy is +/– 2%.

Due to the updates reported in line item 21.2 Surface water allocation announcements - urban water system the value reported in the 2011–12 year has been restated from 597,366 ML to 628,646 ML.