National Water Account 2019

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Key findings

Climate and water

Water Accounting Statements

Supporting information

Region description

Reference information

Melbourne: Governance

Accountability statement

1. This water accounting report has been prepared and presented in accordance with the Australian Water Accounting Standard 1, with the following exceptions:

• No Assurance Statement was prepared because the practice of assurance of water accounting reports are currently not available.
• No information is disclosed about material events that occurred after 30 June 2019, such as extreme precipitation and significant water rights purchases. This information is publicly available elsewhere.
• The volumes of water assets and water liabilities including the volumes of changes to water assets and water liabilities that failed the recognition criteria were reported in the water accounting statements with dashes ('–') in order to highlight data and knowledge gaps that may affect the water accounting statement balances.

2. The report has been compiled from the best data available, as detailed in the water accounting statement Notes, in the time available to compile it from a number of sources. The Bureau of Meteorology takes a nationally-consistent approach to report preparation and presentation.

3. All significant and specific interpretations of the Australian Water Accounting Standard 1 for the purpose of the preparation of this report are explained in the 'Water accounting policies' note. The Bureau of Meteorology is responsible for these interpretations.

Dr Robert Argent

General Manager, Water

Bureau of Meteorology

21 February 2020

Water accounting policies

Introduction

The information presented in the Melbourne region water accounting report is based on collaboration between the Bureau of Meteorology and:

• Victorian Department of Environment, Land, Water and Planning
• Melbourne Water
• City West Water
• South East Water
• Yarra Valley Water
• Western Water
• Southern Rural Water
• Gippsland Water

This report has been 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 accounting is megalitres (ML). Where a reported volume is negative, it is shown in brackets. The applicable reporting period is from 1 July 2018 to 30 June 2019.

Recognition of water assets and water liabilities

Only water that is held or managed by the State licensing authority or the urban retail water authorities and from which future benefit can be derived by stakeholders of the region is defined as a water asset.

Water liabilities are constituted by present commitments to supply water, the discharge of which is expected to result in a probable decrease of the region's water assets or a probable increase in another commitment to supply water.

Provided its volume can be quantified in a way that is complete, neutral, and free from material error, the volume of the water asset or water liability is recognised in the Statement of Water Assets and Water Liabilities.

Water held in storages that has already been abstracted from the entitlement system is deemed not to be part of the region (regardless of the storage's size or connection to the system). This is because the attendant water right has already been exercised.

Recognition of changes in water assets and water liabilities

The increases and decreases to the reported water assets and water liabilities consist of changes that can be quantified in a way that is complete, neutral, and free from material error. These volumes are presented in the Statement of Changes in Water Assets and Water Liabilities and the Statement of Water Flows.

Precipitation and evaporation are recognised only in relation to the surfaces of open storage and river volumes. They do not represent all precipitation, evaporation, and evapotranspiration within the region (notably, these processes occurring from the landscape are not captured).

The portion of runoff that flows into the surface water store (storages and river channels) is quantified and recognised in the Statement of Changes in Water Assets and Water Liabilities. This runoff includes precipitation captured in the catchment less evaporation and infiltration, and is recorded as runoff to surface water.

Allocation announcements on regulated entitlements have been recognised as increases in water liabilities. Note that the definition of regulated or unregulated entitlements for the purpose of the National Water Account (refer to 'Glossary') may be different to the meaning applied by the jurisdiction. Please refer to the Water access and use note for more information on the allocations.

Water assets and water liabilities that fail the recognition criteria

There were no items to report under this category.

Changes to water assets and water liabilities that fail the recognition criteria

The volumes of several changes to water assets identified in the Melbourne region were not reported in the water accounting statements but replaced by dashes ('–') as they 'failed the recognition criteria' specified in the Australian Water Accounting Standard 1, because:

• they could not be quantified in a way that is complete, neutral, and free from material error, and/or
• they were unlikely to provide a future benefit to the region or the region's stakeholders.

The volumes that failed the recognition criteria include groundwater discharge to surface water, as well as groundwater discharge to the landscape.

Restatement of comparative information

In accordance with the Australian Water Accounting Standard 1, comparative year volumes must be restated in the statements if there is a prior period error or a change in item presentation. Comparative year volumes are not required to be restated if there is a change in scope or methodology, or subsequent data availability for the quantification of an item.

Surface water store

Comparative year volumes related to the surface water store were restated from the 2014–2018 Accounts due to a change in presentation. In previous accounts, Thomson Reservoir was not considered as a surface water asset for the region as it is located outside of the region boundary. In this account, however, given that the reservoir is primarily used as water supply for the region's urban water system, Thomson Reservoir has been included as a water asset. The comparative year items restated in this account include:

• Storages
• Precipitation
• Evaporation
• Inter-region inflow
• Delivery: inter-region
• Claims: inter-region
• Allocations: urban system
• Adjustment and forfeiture: urban system.

Additional items such as river storage, runoff, flood return, overbank flow, outflow, and groundwater recharge to the landscape were also restated in this account using an updated methodology. These items were not directly affected by the inclusion of Thomson Reservoir as an asset; however, these items were important to change given their relationship to the items listed above. 

Water use

The following comparative year volumes related to water use were restated from the 2017 Account due to prior period errors:

• Allocation remaining: individual users
• Allocated diversion: individual users
• Adjustment and forfeiture: individual users
• Non-allocated diversion: individual users.

Urban water system

Comparative year volumes for some urban flow volumes were restated from the 2014 and 2015 Accounts due to a change in presentation associated with amendments to the Water Regulations. Leakage from the urban system to either groundwater and the landscape, previously two separate items, were reclassified as a single leakage item in the 2016 Account.

Between-store flows

In the 2014–2017 Accounts, transactions between water assets and water liabilities within the region (e.g. between the surface water store and the groundwater store) were not reported in the water accounting statements. In this account, however, these between-store transactions were included as they provide a better understanding of the water movement that occurs at each water store or system. Comparative year volumes for these transactions are also reported.

Reconciliations

Introduction

The following reconciliation tables verify:

• how the region’s closing water storage in the Statement of Water Flows reconciles to the total water assets reported in the Statement of Water Assets and Water Liabilities
• how the region’s change in water storage in the Statement of Flows reconciles to the change in net water assets reported in the Statement of Changes in Water Assets and Water Liabilities.

Closing water storage to total water assets

* between-store claims

Net change in water storage to the change in net water assets

* between-store claims / liabilities