The information presented on the Melbourne region is based on agreements between the Bureau of Meteorology (the Bureau) and reporting partners, including:
The report was prepared using an accrual basis of water accounting, with the exception of the physical water flow information. The water attribute being quantified is volume and the unit of account is megalitres (ML).
Only water that is held or managed by the state licensing authority or the urban utility, and which is part of the entitlement system, is defined as a water asset. Provided its volume can be quantified with representational faithfulness (WASB 2009), the asset is recognised in the Statement of Water Assets and Water Liabilities. Where a water asset or water liability does not meet the recognition criteria, it is reported in the Statement of Water Assets and Water Liabilities with a dash (–). Water held in storages that was already abstracted from the entitlement system is deemed not to be part of the water report entity (regardless of its size or connection to the system). This is because the attendant water right was already exercised.
Line item 1.2 Unregulated channel is recognised as a water asset for the channel reaches for which reliable data are available to quantify the volume with representational faithfulness. For the other channel reaches, water in the unregulated channel connected surface water is not recognised in the water accounting statements.
Although water within Line item 1.3 Regulated channel is a vital water asset for the conveyance of water within the water report entity, it cannot be quantified with representational faithfulness because reliable data are not available.
The volume of water within Line item 1.4 Lakes and wetlands – connected cannot be quantified with representational faithfulness because reliable data are not available. The volume of water held in lakes and wetland is relatively small in size and its omission does not have a material impact on the total water resource available. It is recognised that water within Line item 1.4 makes a significant contribution to environment benefits in the water report entity.
Line item 2 Groundwater store assets within the Melbourne region are quantified for prescribed management units only.
Regarding Line item 5 Water distribution system store, it is considered that the pipes are always full and may hold a large volume of water, but the omission of the volume from the Statement of Water Assets and Water Liabilities is not considered material because the volume is nearly the same throughout the year.
The increases and decreases to the water assets and water liabilities reported consist only of changes that can be quantified with representational faithfulness (WASB 2009). Where a change to a water asset or water liability does not meet the recognition criteria, it is reported in the Statement of Changes in Water Assets and Water Liabilities and the Statement of Physical Water Flows with a dash (–). These increases and decreases form part of Line item 30 Unaccounted-for difference and are explained in the notes.
Precipitation and evaporation (Line item 13.1 Precipitation on connected surface water and Line item 14.1 Evaporation from connected surface water) are only recognised in relation to storage surfaces and unregulated river channels for which volumes are provided in the water accounting statements. It does not represent all precipitation and evaporation within the physical region of the water report entity. Notably, these processes occurring from the landscape are not captured.
Reference: Water Accounting Standards Board (WASB) 2009, Statement of Water Accounting Concepts 3 Qualitative Characteristics of General Purpose Water Accounting Reports (SWAC 3), Canberra.
National Water Account 2010
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