Melbourne

                                                                                                   

14.9 Diversion of surface water for transfer-out under interbasin agreement

                             

Supporting information   


The volume recognised in the water accounting statements (681 ML) represents the total volume of water transferred out of the Melbourne region under the Bulk Entitlement (Tarago River – Gippsland Water) Conversion Order 2009 during 2009–10.

The volume recognised in the water accounting statements (681 ML) represents the volume of water exported from the water distribution system to Gippsland Water and to Western Water service areas (around Woodend) outside of the Melbourne region. Gippsland Water receives water from the Tarago catchment to supply districts mainly to the east of the Melbourne region.

Under the Bulk Entitlement (Tarago River – Gippsland Water) Conversion Order 2009, Gippsland Water may take 4,825 ML over any five consecutive years to supply Drouin and Neerim South (Bunyip catchment, within the Melbourne region) and Warragul (Latrobe catchment, adjacent to the Melbourne region).

The service area of Western Water includes towns both inside and outside the Melbourne region. The town of Woodend, for example, lies outside the Melbourne region but receives water sourced from within the region.

The table below shows the breakdown of water exported from the water distribution system within the Melbourne region during 2009–10.



Volume of water exported from the water distribution system within the Melbourne region
Water exported Volume (ML)
Non-potable water exported from Melbourne Water via the Tarago catchment to Gippsland Water

546
Potable water supply from Western Water to Woodend

58
Non-potable water supply from Western Water to Woodend from Macedon storage

77
Total

681

 

Quantification approach   


Data source

Melbourne Water: Waterworks database.
Western Water: IT database.

Data provider

Melbourne Water and Western Water.

Method

The total volume of water transferred out of the region was the sum of a number of components that are provided from different water utilities, as described below.

Melbourne Water
This item represents the total metered volume of non-potable water provided to Gippsland Water from the Tarago Catchment at the following locations:

  • Tarago–Westernport Pipeline at Rokeby (to supply Warragul and Drouin)
  • Tarago Reservoir (to supply Neerim South and Noojee).


Western Water
This item represents the total metered volume of potable and non-potable water exported from Western Water. Meters are located on inflow pipelines to Woodend reservoirs. Weekly readings are taken from these meters.

Uncertainty

  • Melbourne Water: Metered data. Estimated uncertainty is ungraded.
  • Western Water: Derived from metered data. Estimated uncertainty is +/–5%.
  • The uncertainty value provided by Western Water refers to the Essential Services Commission’s standard confidence grades, as detailed in its June 2005 guideline for Approving, Conducting and Reporting Audits for Victorian Water Businesses (ESC 2005). Refer to Water Industry Regulatory Audits 2010, Audit Report (ESC 2010), prepared for Western Water, October 2010.

Approximations, assumptions, caveats/limitations

Nil.