Perth
9.9 Discharge from urban water system

Supporting Information

a. Internal transfer of water from the urban water system to storages

Volume of water transferred to surface water storages from the urban water system during the 2010–11 year is given in the following table. The water transferred from the urban water system is a combination of surface water, groundwater and desalinated water. These internal water transfers occur in order to store winter production of desalination water and groundwater and to balance the storages to prevent overflow and enable summer peak supply capacity.

 

Volume of water internally transferred to storages from the urban water system during the 2010–11 year

Storage

Volume (ML)

Canning

17,624

Lower Helena

24,390

North Dandalup

2,871

Serpentine Pipehead

16,016

Victoria(a)

4,078

Wungong Dam

6,364

Total water transferred

71,343

(a)  Water transfer is direct to Victoria Reservoir and via Bickley Pumpback Reservoir.

 

b. Discharge of treated wastewater into rivers

Volume of treated wastewater discharged from wastewater treatment plants into rivers during the 2010–11 year is given in the following table.

 

Volume of treated wastewater discharged to rivers and drains during the 2010–11 year

Wastewater treatment plant

Total outflow (ML)

Harvey

178

Waroona

70

Williams

15

Total discharge to rivers

263

 

c. Transfer of water from pumpback reservoirs into storages

Volume of water transferred to surface water storages from each pumpback reservoir during the 2010–11 year is given in the following table. Water is collected in these pumpback reservoirs on an opportunistic basis and transferred back to the main surface water storage in order to settle (i.e. reduce turbidity) and become part of the water supply source for that storage.

 

Volume of water transferred to storages from pumpback reservoirs during the 2010–11 year

Pumpback reservoir

Volume (ML)

Lower South Dandalup (to South Dandalup)

673

 

Quantification Approach

Data Source

Water Corporation: Operational Data Storage System database.

Provided by

Water Corporation.

Method

The volume of water transferred from the urban water system to surface water storages is based on measured inflow data at the storages.

The volume of water discharged to rivers from the Williams, Waroona and Harvey Treatment Plants are based on measured discharge data collected by flow meters installed at the sites.

Assumptions, Limitations, Caveats and Approximations

Nil.

Uncertainty Information

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 (Guidelines for water meter installation 2009).

Comparative year

The following table presents substantive changes in the line item reported in this 2011 Account with the corresponding line item in the 2010 Account.


Comparative year information for line item 9.9

2011 Account line item

2010 Account line item

2011 Account volume for the 2009–10 year (ML)

2010 Account volume for the 2009–10 year (ML)

Change from the 2010 Account to the 2011 Account

9.9 Discharge from urban water system

13.8 Other lumped surface water increases

45,233

45,233

Change in line item name and number