Melbourne
19.4 Delivery to urban water system users

Supporting Information

The volume presented in the water accounting statements (343,166 ML) represents delivery of water from retail and rural water authorities to their end users and to the irrigation schemes in the Melbourne region during the 2010–11 year.

Delivery to urban system users
Water authority Type of water Purpose Volume (ML)
City West Water Potable Residential 46,318
Commercial, industrial, municipal 37,804
Recycled Commercial, industrial, municipal 137
Subtotal for City West Water 84,259
Melbourne Water Recycled Recycled water supply to Eastern Irrigation Scheme 1,666
Conservation flows to wetlands within the Western Treatment Plant 18,723
Subtotal for Melbourne Water
20,389
South East Water Potable Residential 81,650
Commercial, industrial, municipal 27,195
Non-potable Residential, commercial, industrial, municipal 62
Other 4
Recycled Residential 102
Commercial, industrial, municipal 446
Agricultural/individual irrigation 793
Subtotal for South East Water 110,252
Southern Rural Water Potable Bacchus Marsh Irrigation District 45
Recycled Werribee Irrigation District 1,746
Werribee Tourist Precinct 43
Subtotal for Southern Rural Water 1,834
Western Water Potable Residential 7,594
Commercial, industrial, municipal 1,447
Recycled Residential 5
Commercial, industrial, municipal 12
Agricultural/individual irrigation 2,743
Subtotal for Western Water 11,801
Yarra Valley Water Potable Residential 89,661
Commercial, industrial, municipal 24,100
Non-potable Residential 48
Commercial, industrial, municipal 250
Recycled Residential 61
Commercial, industrial, municipal 310
Agricultural/individual irrigation 201
Subtotal for Yarra Valley Water 114,631
Total 343,166

Quantification Approach

City West Water

Data Source

City West Water Gentrack billing system.

Provided by

City West Water.

Method

The volume of water delivered to end users from City West Water was the sum of the following components.

Potable water for residential use:

City West Water has over 320,000 meters; residential meters are read on a quarterly basis. Generally, non-residential customers consuming greater than 10 ML per annum are read monthly and those that consume less than 10 ML are read quarterly.

Volumes are derived from monthly and quarterly meter readings, which are used to bill non-residential and residential customers. City West Water's Gentrack billing system collates all meter readings from residential and non-residential customers. Volumes are applicable to the 2010–11 year.

Recycled water supplied for commercial, industrial and municipal use

This item represents the metered volume of recycled water purchased and received from Melbourne Water's Western Treatment Plant. Data is collected from flow meters and an electronic logger capture system.

Assumptions, Limitations, Caveats and Approximations

Volumes are only applicable to water use within the City West Water service area inside the Melbourne region. There was no residential supply to Little River during the 2010–11 year.

Uncertainty Information

Uncertainty of this item is +/– 5% according to meter specifications

Melbourne Water

Data Source

Melbourne Water.

Provided by

Melbourne Water.

Method

Recycled water supply to customers

Recycled water supplied to other water authorities and private organisations is measured with magnetic flow meters at the interface of Melbourne Water and the receiving authority. The Western Treatment Plant logs data daily and reports quarterly. The Eastern Treatment Plant logs data daily and reports monthly.

Conservation flows to wetlands within the Western Treatment Plant

Water recycled and used for conservation flows is metered using an ultrasonic level transmitter. This recycled water is measured by Melbourne Water before being discharged to the Lake Borrie wetlands (Ramsar listed).

Ultrasonic level transmitters are used to measure flows and are assumed to have an accuracy of +/–10%.

Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

Recycled water supply to customers
Magnetic flow meters are used to measure these flows and are assumed to have an accuracy of +/– 2%.
Conservation flows to wetlands within the Western Treatment Plant

Ultrasonic level transmitters are used to measure flows and are assumed to have an accuracy of +/– 10%.

South East Water

Data Source

South East Water HiAffinity database.

Provided by

South East Water.

Method

The volume of water delivered to end users from South East Water was the sum of the following components.

Potable water for residential, commercial, industrial and municipal use
The item represents the quarterly metered volume of potable water supplied for residential use. Most of the meters were located at property boundaries.

Non-potable water for residential, commercial, industrial and municipal use
The item represents the quarterly (some large users are monthly) metered volume of potable water supplied for commercial, industrial and municipal use. Most of the meters were located at property boundaries. This value is the total non-residential water use

Recycled water for residential, commercial, industrial, municipal, agricultural and individual irrigation
This item represents the quarterly metered volume of recycled water supplied for residential, commercial, industrial and municipal use.

Assumptions, Limitations, Caveats and Approximations

Assumes meters and readings are accurate.

Data reported from 01 July 2010 – 30 June 2011 are based on the four quarterly readings on each property. The water year for properties read early in the cycle starts in April and are billed in July. Later readings in the cycle have a meter year that starts in June and is billed in September.

Some quarterly readings are estimated (due to issues such as meter inaccessibility) and will be adjusted in following periods.

Uncertainty Information

Potable and non-potable water for residential, commercial, industrial and municipal use

Water Industry Regulatory Audits 2011,  October 2011 (WIRA 2011)indicated that reliability and accuracy for metered volume of potable water delivered is +/– 5% (i.e. Grade 2).

Recycled water for residential, commercial, industrial, municipal, agricultural and individual irrigation:
+/– 5% in accordance with the WIRA 2011 independent annual audit report.

Southern Rural Water

Data Source

Melbourne Water Waterworks database, Western Water IT database.

Provided by

Melbourne Water and Western Water.

Method

The volume of water delivered to end users from Southern Rural Water was the sum of the following components:

Potable water supplied to Bacchus Marsh Irrigation District
The item represents the total metered volume of potable water supplied to Southern Rural Water via Western Water's infrastructure.

Recycled water supplied for Werribee Irrigation District and Werribee Tourist Precinct

This item represents the total metered volume of recycled water supplied from Melbourne Water's Western Treatment Plant to Southern Rural Water. All water that is recycled for supply to other water authorities from Melbourne Water is measured with magnetic flow meters at the interface of Melbourne Water and the receiving authority. The Western Treatment Plant logs data daily and reports quarterly.

Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

Meters are generally ultrasonic flow meters for larger pipes (greater than 600 mm diameter) and magnetic flow meters for smaller pipes (less than 600 mm diameter). Both types of meters have an accuracy of +/– 1% as reported by the manufacturers.

Western Water

Data Source

Western Water information technology database water usage spreadsheet.

Provided by

Western Water.

Method

The volume of water delivered to end users from Western Water was the sum of the following components.

Potable water for residential, commercial, industrial and municipal use:
This item represents the total, monthly and four-monthly metered volume of potable water supplied for residential use, excluding potable water supplied to Woodend.

Non-potable water for residential, commercial, industrial and municipal use

This item represents the total metered volume of potable water supplied for commercial, industrial and municipal use, but excludes potable water supplied to Woodend. Meters are located at the owners' individual properties. Meters are read every four months.

Recycled water for residential use
This item represents the total metered volume of recycled water supplied for residential use. The meter is located at the outflow from the class tank. All non-residential volumes are subtracted, leaving a residential use total. Meters are read monthly.


Recycled water for commercial, industrial, municipal, agricultural and individual irrigation

This item represents the total metered volume of recycled water supplied for commercial, industrial, municipal uses and agricultural use. Meters are located at customer properties and are read monthly.



Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

+/– 5% in accordance with Summary Audit Report – October 2010 (Essential Services Commission 2010) .

Yarra Valley Water

Data Source

Yarra Valley Water quarterly billing database

Provided by

Yarra Valley Water

Method

The volume of water delivered to end users from Yarra Valley Water was the sum of the following components:

Potable water for residential, commercial, industrial and municipal use

The item represents the metered volume of potable water supplied for residential, commercial, industrial and municipal use.

Customer usage is calculated as the difference between total water received and estimated non-revenue water volume, and is then divided into residential and non-residential components in the same ratio as the customer-billed volumes.

Non-potable water for residential, commercial, industrial and municipal use
The item represents the quarterly (some large users are monthly) metered volume of potable water supplied for commercial, industrial and municipal use. Most of the meters were located at property boundaries. This value is the total non-residential water use.

Recycled water for residential, commercial, industrial, municipal, agricultural and individual irrigation:

This item represents the metered volume of recycled water supplied to the Aurora recycled water development scheme for residential use as well as some small volumes from Brushy Creek and Wallan treatment plants. The volume is derived from the billed volume of recycled water through third pipe schemes to residential customers.

Assumptions, Limitations, Caveats and Approximations

  • customer usage in the reporting period is the difference between the total water received and the estimated level of nonrevenue water
  • residential and non residential usage volumes are in the same proportion as billed and metered volumes
  •  billed volumes over the four quarters provide an adequate estimate of water used in the reporting period.

 

Uncertainty Information

+/–5%.

Comparative year

This line item was not reported in the 2010 Account. In the 2010 Account, the urban users were included in the region's definition. In the 2011 Account, the urban users were excluded from the region's definition. This change was made to allow reporting, in the water accounting statements, on urban water use (as a water asset decrease) and wastewater collection (as a water asset increase), as both were considered useful information to the National Water Account users.

This change was considered material and increased the accuracy and comparability of the information provided to the users of the National Water Account.The comparative year volume is 322,660 ML.