1.5 Inter-region claim on water

Supporting Information

This line item represents the Sydney Catchment Authority's (SCA) entitlement to the Fish River Water Supply Scheme (FRWSS) during the 2011 Account.

The inter-basin claim remaining at the beginning of the 2010–11 year was 0 ML.

In addition to its own storages, the SCA has an annual maximum allocation entitlement from the FRWSS to supply water to the Blue Mountains. This entitlement is subject to a number of operating rules and restrictions depending on levels in the supply storage (Oberon Dam).

The amount of water available to SCA under the FRWSS depends on the levels of the supply storages.

Over the 2010–11 year the following restriction levels were applied.

Restriction levels applied during the 2011 Account

Date restrictions levels were in place

Restriction level

Allowable diversion (ML/day)

30 June 2010 to 18 July 2010

Level 6


19 July 2010 to 15 August 2010

Level 5


16 August 2010 to 22 August 2010

Level 4


23 August 2010 to 29 August 2010

Level 3


30 August 2010 to 5 December 2010

Level 2


6 December 2010 to 2 March 2011

Level 1


From 3 March 2011

All restrictions lifted


This resulted in the total cumulative allocation for the year of 3,028 ML.

On 30 June 2010, the SCA was also entitled to 1,825 ML carry-over (banked) volume from the FRWSS at the beginning of the 2010–11 year. This right to the carry-over volume of water had been suspended since March 2010 because Oberon Reservoir fell below 10% capacity and remained suspended on 30 June 2010. At this time, the SCA was still able to draw water from the FRWSS under their allocation entitlement but not from the carry-over volume. On 7 March 2011, the carry-over (bank) was deleted and a new carry-over rule instated.

By 30 June 2011 the SCA had a carry-over of 119 ML.

Therefore, the total volume allocated to the SCA under the FRWSS  for the 2011 Account was 4,853 ML. Reconciliation of this line item is shown in the following table.

Calculations of the inter-region claim on water for the 2010–11 year
Line item
Volume (ML)


1.5 Inter-region claim on water – opening balance



9.15 Increase of inter-region claim on water



9.11 Delivery of water under inter-region agreement



17.17 Decrease of inter-region claim on water



1.5 Closing balance (as at 30 June 2011)


Quantification Approach

Data Source

SCA databases.

Provided by



Carry-over volume available at the beginning of a year from the FRWSS is calculated from entitlement holder's allocation and metered supply volume for the previous two years (carry-over volume is a two-year rolling average computed every six months; the carry-over volume is capped at 50% of the maximum annual quantity). The metered supply volume to the SCA is based on flow measurements using a turbine helix-type flow meter. 

Assumptions, Limitations, Caveats and Approximations


Uncertainty Information

Carry-over volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 2%.

Comparative year

The following table compares the value at 30 June 2010 reported in this account with the corresponding value reported in the 2010 Account.


Comparative information from the 2010 Account for line item 1.5

2011 Account line item

2010 Account line item

Value reported in the 2010 Account (ML)

Value reported in the 2011 Account (ML)

Additional information

1.5 Inter-region claim on water

7.1 Inter-basin claim on water – remaining



Change in line item name