17.17 Decrease of inter–region surface water claim on water

Supporting information

The volume presented in the water accounting statements (20,791 ML) represents the decrease to the claim that Melbourne retail authorities City West Water, South East Water and Yarra Valley Water are entitled to under:

  • bulk entitlement for Thomson Reservoir
  • bulk entitlement for Silver and Wallaby creeks
  • agreement for water held in Lake Eildon.

The following table presents the breakdown of decreases to inter–region claims for the Melbourne region during the 2011–12 year.

Decrease of inter–region surface water claim on water
Component Volume (ML)
Thomson Reservoir Evaporation 12,631
Allocation adjustment 2,000
Silver and Wallaby creeks n/a 0
Lake Eildon Evaporation 2,521
Spills 3,639
Total 20,791

Quantification approach

Data source

Waterworks database.

Provided by

Melbourne Water.


Decreases to inter–region claims held by the Melbourne region were calculated using the following methods:

Thomson Reservoir

Evaporation of the Melbourne retailer's share of storage in Thomson Reservoir is determined using the Pan Evaporation method.

Assignments of Water Allocation – Southern Rural Water and Western Water 2011. The Minister approved a 2,000 ML transfer from the retailers to Southern Rural Water's Thomson Reservoir account as of 10th December 2011. These assignments are the result of an agreement between Southern Rural Water and Western Water to assign 2,000 ML of water allocation to the Macalister Irrigation District as payback for water provided to Southern Rural Water's Western Irrigation Business in 2007–08.

Silver and Wallaby creeks

There were no decreases to the inter–region claim on water from Silver and Wallaby creeks during the 2011–12 year.

Lake Eildon

Evaporation: five percent of the water held in Lake Eildon for the Melbourne region is subtracted on 01 July each year to account for annual evaporation, as per the Carryover for water shares in the Murray, Goulburn and Campaspe water systems 2010.

Assumptions, limitations, caveats and approximations


Uncertainty information

The uncertainty estimate was not quantified.