Perth

The public water system within the Perth region primarily supplies water to two areas: the Perth metropolitan area and the southwest region (including Mandurah). Public water system-related line item values in the Water Accounting Statements report water supply to both these areas.

In this section, public water supply is reported for the:

• greater Perth region (i.e. the Perth metropolitan area and the southwest region)
• Perth metropolitan area only, which is referred to as the Integrated Water Supply Scheme.

The data relating to the public water supply system for the Perth region was provided by the Water Corporation and the Department of Water.

The tables below provide details of water abstractions, usage and recycling that occurred within the greater Perth region and the Perth metropolitan area only, during the 2009-10 reporting period.

The figure below is a schematic of the water movements through the public water supply system.

Note: Breakdown based on percentage use data obtained from the Perth Residential Water Use Study 2008-2009 (Water Corporation 2009).

NA = not available

Schematic flow diagram of the public water supply system for the greater Perth region

Schematic flow diagram of the public water supply system for the Perth metropolitan area

U1 Volume of water taken from surface water for water supply

141,276 ML (Perth metropolitan: 107,421 ML)

See line item 19.8.5.

U2 Volume of water taken from groundwater for water supply

120,828 ML

See line item 19.8.7.

U3 Delivery of desalinated water transferred-in to the urban potable water supply system

47,693 ML

See line item 19.5.1.

U4 Volume of non potable water import

O ML (Perth metropolitan: 16,503 ML)

This line item is not applicable to the greater Perth region as no water is imported from outside the region boundary. However, for the Perth metropolitan area, water is abstracted from Samson and Stirling reservoirs, located within the southwest region, for public water supply to the Perth metropolitan area.

U6 Volume of potable water discharge to surface water from urban water supply system

45,233 ML

See line item 13.8.

U9 Volume of potable water supplied for residential use

175,330 ML (Perth metropolitan: 163,416 ML)

Data source

Water Corporation: Operational Data Storage System.

Data provider

Water Corporation.

Method

The amount of potable water used for residential use (U9), commercial, industrial and municipal use (U10) and all other uses (U11) is estimated as a percentage of the total water supply based on the Perth Residential Water Use Study 2008-2009 (Water Corporation 2009). (The category all other uses includes agriculture use, non-revenue water [system leakage] and environmental flows.)

The volume of water used by consumers within the public water supply system is the total potable water supplied to the system minus any leakage and internal transfers, as shown in the table below.

 The amount of water used for residential use; commercial, industrial and municipal use; and all other uses during 2009-10 is calculated as shown in the table below.

Uncertainty

Expected error for water meters is +/- 5%.

The Department of Water requires that all water meters, when tested in situ conditions, must be within 5% accuracy across the full flow rate range (Department of Water 2009).

Approximations, assumptions, caveats/limitations

Actual water use is not measured. The values reported here are estimates only.

U10 Volume of potable water supplied for commercial, industrial and municipal uses

46,919 ML (Perth metropolitan: 43,731 ML)

See line item U9.

U11 Volume of potable water supplied other than for residential, commercial, municipal and industrial uses

24,695 ML (Perth metropolitan: 23,016 ML)

See line item U9.

U15 Background leakage from potable water supply system

11,909 ML (Perth metropolitan: 11,337 ML)

See line item 15.2.4.

U19 Volume of wastewater collected

129,375 ML (Perth metropolitan: 124, 559 ML)

Total wastewater inflow volumes into each treatment plant during 2009-10 are given below.

Data source

Water Corporation: Operational Data Storage System.

Data provider

Water Corporation.

Method

Total inflow into each wastewater treatment plant within the Perth region is based on measured discharge data collected by flow meters installed at each site.

Uncertainty

This value is estimated to be in the range of +/- 5-10%.

Approximations, assumptions, caveats/limitations

Nil.

U22 Volume of treated wastewater discharge to landscape

4,608 ML (Perth metropolitan: 120 ML)

See line item 20.4.3.

U23 Volume of (treated) wastewater discharged to sea or out of entity

116,507 ML

See line item 20.4.2.

U32 Volume of recycled water supplied for commercial, industrial and municipal uses

3,857 ML (Perth metropolitan: 3,571 ML)

This line item refers to the treated wastewater used for local industry.

Total volume of treated wastewater recycled from each treatment plant during 2009-10 is given below.

Data source

Water Corporation: Operational Data Storage System.

Data provider

Water Corporation.

Method

Recycled water from two wastewater treatment plants is sold for industrial use. The volume of recycled wastewater is based on measured discharge data collected by flow meters installed at each site.

Uncertainty

This value is estimated to be in the range of +/- 5-10%.

Approximations, assumptions, caveats/limitations

Nil.

U33 Volume of recycled water supplied other than for residential, commercial, municipal and industrial uses

1,475 ML

See line item 15.2.6.

U34 Volume of recycled water used on-site or in-process

2,233 ML (Perth metropolitan: 2,163 ML)

This line item refers to the treated wastewater used for on-site use.

The total volume of treated wastewater recycled for on-site use from each treatment plant during 2009-10 is given below.

Data source

Water Corporation: Operational Data Storage System.

Data provider

Water Corporation.

Method

Recycled water from four wastewater treatment plants is sold for on-site use. The volume of recycled wastewater is based on measured discharge data collected by flow meters installed at each site.

Uncertainty

This value is estimated to be in the range of +/- 5-10%.

Approximations, assumptions, caveats/limitations

Nil.

U35 Volume of recycled water used for local irrigation

351 ML (Perth metropolitan: 342 ML)

This line item refers to the treated wastewater used for local irrigation (i.e. parks and recreation grounds).

The total volume of treated wastewater recycled for local irrigation from each treatment plant during 2009-10 is given below.

Data source

Water Corporation: Operational Data Storage System.

Data provider

Water Corporation.

Method

Recycled water from three wastewater treatment plants is used for local irrigation. The volume of recycled wastewater is based on measured discharge data collected by flow meters installed at each site.

Uncertainty

This value is estimated to be in the range of +/- 5-10%.

Approximations, assumptions, caveats/limitations

Nil.