1.5 Inter-region claim on water

Supporting information

The volume of 2,367 ML represents the carryover associated with the Fish River Water Supply Scheme for Sydney Catchment Authority and Delta Electricity for the 2012–13 year. 

Each agency has an annual maximum allocation entitlement from the Fish River Water Supply Scheme to supply water to their storages. This entitlement is subject to a number of operating rules and restrictions depending on the levels observed in the supply storages (Oberon Dam and Duckmaloi Weir). There is also the ability to carryover a maximum of 20% of the total allocation into the following year.

No restrictions were in place over the entire 2012–13 year, therefore the maximum allocation limits and carryover volumes were applicable for the 2012–13 year. These are detailed in the following table.

Maximum allocation limits and carryover for the Fish River Water Supply Scheme during the 2012–13 year


Maximum allocation entitlement (ML)

Carryover as at 30 June 2013 (ML)

Carryover as at 30 June 2012 (ML)

Delta Electricity




Sydney Catchment Authority








Quantification approach

Data source

New South Wales Office of Water Fish River Water Supply Scheme Weekly Use Report 2012–13; Sydney Catchment Authority databases.

Provided by

New South Wales Office of Water; Sydney Catchment Authority.


The allocation remaining at 30 June 2013 was calculated as shown in the following table.

Volume of inter-region claim on surface water remaining at the start and end of the 2012–13 year






Opening balance (as at 30 June 2012)



9.15 Increase of inter-region surface water claim on water



9.11 Delivery of water under inter-region agreement to surface water



17.17 Decrease of inter-region claim on water



Closing balance (as at 30 June 2013)



Carryover volume available at the beginning of a year from the Fish River Water Supply Scheme is calculated from entitlement holder's allocation and metered supply volume for the previous two years. Carryover volume is a two-year rolling average computed every six months. The carryover volume is capped at 50% of the maximum annual quantity. The metered supply volume to the Sydney Catchment Authority is based on flow measurements using a turbine helix-type flow meter.

Assumptions, limitations, caveats and approximations


Uncertainty information

Delivery volumes are based on measured data. Estimated uncertainty based on meter accuracy is +/–2%.

Comparative year

The volume of 2,723 ML originally reported in the 2011–12 year included the volume of carryover held by Lithgow City Council. This volume is now reported within the urban water store and is accounted in 3.4 Urban inter-region claim on water. Therefore the volume of water reported in the 2011–12 year has been adjusted to 2,367 ML.