Melbourne
1.1 Storages

Supporting Information

The volume presented in the water accounting statements (669,642 ML) represents the volume of water held in surface water storages in the Melbourne region at the end of the 2010–11 year.

The volume presented is the sum of the volume held in water storages that have a total storage capacity over 1,000 ML, including the volume of dead storage. The following table presents a breakdown of individual storages in the Melbourne Region.

Water storages
Storage name Storage
operator		 Total storage
capacity		 Dead
storage		 Storage volume
30 June 2010 30 June 2011
O'Shannassy Melbourne
Water		 3,123 n/a 3,155 3,235
Yan Yean 33,125 2,859 14,056 30,229
Greenvale 27,501 662 17,661 21,382
Maroondah 28,233 6,054 16,826 28,393
Silvan 40,581 136 36,067 34,674
Cardinia 288,964 2,053 103,332 206,406
Upper Yarra 204,985 4,406 118,124 142,602
Sugarloaf 99,222 2,969 61,371 98,552
Tarago 37,580 n/a 21,784 24,000
Rosslynne Southern
Rural
Water		 25,400 150 1,148 16,716
Pykes Creek 22,119 1,770 1,196 22,119
Merrimu 32,215 335 3,047 27,757
Melton 14,360 140 2,879 13,577
Total
857,408 21,534 400,646 669,642

The volume of water held in water storages increased significantly between the start and end of the reporting period. Very high rainfall, generated by one of the strongest La Nina events on record, resulted in water storages recording their highest inflows since the drought commenced in 1997. 

Thomson Reservoir is not included in the storages as it is located outside of the Melbourne region boundary.

Quantification Approach

Data Source

Bureau of Meteorology: water storages, Australian Water Resources Information System.

Provided by

Bureau of Meteorology.

Method

Storage volume was measured at the start and end of the reporting period by using gauged water level height(s) in metres, Australian height datum (mAHD) for individual storages. The height measurement was converted to a volume using the storage-volume curve(s) provided by the managing authority.

Storage capacity was calculated using the full supply level (FSL), and coverting it to a volume using the storage volume curve(s) provided by the managing authority.

Assumptions, Limitations, Caveats and Approximations

  • Storage-volume curves represent specifically surveyed parts of the water storage, and may not reflect the storage-volume relationship across the entire storage.

  • Water storages are subject to sedimentation and other physical changes over time, which in turn affect the accuracy of the storage-volume curves.

  • Storage capacity may differ from those published on the Water storages page of the Southern Rural Water website due to to rounding and uncertainty in the true values.

  • Southern Rural Water recognise different volumes for managing water allocations according to the Werribee & Bacchus Marsh Allocation Method.

Uncertainty Information

The volume was estimated from measured data.

Comparative year

This item corresponds to line item 1.1 Storages – entitlement system reported in the 2010 Account. Following publication, an error was identified in the volumes reported in the 2010 Account that caused the 2009–10 year value to be restated; the volumes reported did not include dead storage as required by the Exposure Draft of Australian Water Accounting Standards 1.

This change and the respective values are detailed in the following table. The restated comparative year volume at 30 June 2010 is 400,646 ML.

Restated comparative year information for line item 1.1 Storages

2010 Account line items

Volume at 30 June 2010 reported in 2010 Account (ML)

Value difference due to prior period error correction (ML)

Volume at 30 June 2010 reported in 2011 Account (ML)

1.1 Storages – entitlement system

381,507

19,139

400,646