Perth
19.4 Delivery to urban water system users

Supporting information

a. Overview

The volume reported in the water accounting statements (232,315 ML) represents the total volume of water delivered to urban water system users within the Perth region during the 2012–13 year.

This volume is comprised of two components:

  • water supply to users from the urban water supply system (224,810 ML)
  • water supply to users from the recycled water system (7,505 ML).

b. Water supply to users from the urban water supply system

Perth's urban water system comprises three subcomponents:

  • urban water supply system
  • wastewater system
  • recycled water system.

Almost 97% of the water delivered to urban water users during the 2012–13 year came from the urban water supply system (224,810 ML).

During the 2012–13 year, approximately 69% of the urban water supply system outflow was water supply to urban users (224,810 ML). Approximately 22% of the urban water supply system outflows was transferred back to surface water storages (part of 19.5 Discharge from urban water system to surface water). The majority of this water was internal transfers for the storage of desalinated water produced during winter and to balance the storages in preparation for peak summer supply. Less than 1% of the urban water supply system outflows was transferred to Western Australia's southwest region (19.11 Transfer of water outside of region); the remaining outflows was lost through leakage to groundwater (19.3 Urban water system leakage to groundwater) and operational losses (19.20 Other urban water system decreases).

The following figure shows all the inflows and outflows associated with the urban water supply system. For more detail on a particular flow associated with the urban water supply system, refer to the line item notes.


Schematic diagram of water inflows and outflows during the 2012–13 year for Perth's urban water supply system; line item numbers are provided in brackets
Schematic diagram of water inflows and outflows during the 2012–13 year for Perth's urban water supply system; line item numbers are provided in brackets

c. Water supply to users from the recycled water system

Approximately 3% of water delivered to urban water users came from the recycled water system (7,505 ML).

During the 2012–13 year, approximately half of the recycled water produced was delivered to urban users, primarily for industrial and municipal use (including local irrigation). Approximately 24% of the recycled water was used on-site at wastewater treatment plants throughout the region; the remaining recycled water was used to recharge aquifers—via injection wells (19.9 Managed aquifer recharge) or infiltration basins (19.10 Discharge from urban water system to groundwater). The following figure shows all the inflows and outflows associated with the recycled water system.

For more detail on a particular flow associated with the recycled water system, refer to the line item notes. Volumes in the figure annotated with an asterisk (*) indicate flows between subcomponents and are not reported in the account. As such, these flows do not have an associated line item number.


Schematic diagram of water inflows and outflows during the 2012–13 year for Perth's recycled water system; line item numbers are provided in brackets
Schematic diagram of water inflows and outflows during the 2012–13 year for Perth's recycled water system; line item numbers are provided in brackets


Total volume of treated wastewater recycled for further use from each treatment plant during the 2012–13 year is given in the following table.


Volume of recycled water supplied to users from each treatment plant during the 2012–13 year

Wastewater treatment plant

Recycled

(ML)

Use

Perth metropolitan area

 

 

Beenyup
920
on-site process use

Kwinana Reclamation Scheme

4,496

local industry

Mundaring

21

local irrigation

Subiaco

951

local irrigation and on-site process use

Woodman Point
728
on-site process use

Mandurah-Murray area

 

 

Gordon Road

85

local irrigation

Halls Head

6

local irrigation

Pinjarra

245

local industry

Other

 

 

Boddington

26

local industry

Wundowie

27

local irrigation

Total

7,505

 


During the 2012–13 year, the volume of treated wastewater recycled for further use was equivalent to approximately 8% of the total treated wastewater discharged from treatment plants within the region.

 

Quantification approach

Data source

Operational Data Storage System and the Water Corporation Annual Report 2013.

Provided by

Water Corporation.

Method

Total water supply to urban users within the Perth region from the urban water supply system during the year is the total of consumers' meter readings as provided in the Water Corporation Annual Report 2013.

The volume of recycled water supplied to users is based on measured discharge data collected by flow meters installed at the wastewater treatment plant.

Assumptions, limitations, caveats and approximations

The volume of recycled water discharged to users from the Pinjarra Wastewater Treatment Plant was not measured. It was assumed that the recycled volume of water was equal to the measured wastewater inflow to the plant.

Uncertainty information

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

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