11.13 Allocation extraction of groundwater to urban water system

Supporting Information

This line item refers to the volume of water extracted from bore fields for urban water supply.

The volume of water extracted from each bore field for urban water supply during the 2010–11 year is given in the following table.


Volume of groundwater extracted from each bore field for the urban water system during the 2010–11 year

Groundwater source

Total extracted (ML)

Perth city area


















Southwest area




South West Coastal


Total extraction



Only a relatively minor volume of groundwater is allocated for the southwest area (including Mandurah), of which 356 ML was extracted during the 2010–11 year. Most of the urban water supply for this area is supplied from Stirling and Samson Reservoirs.

Quantification Approach

Data Source

Water Corporation: Operational Data Storage System.

Provided by

Water Corporation.


Inflow of groundwater into the urban water system is the total volume of groundwater extracted from the groundwater sources (bore fields) within the Perth region. Total water extracted is based on measured data collected at each source site using a cumulative water meter.

Assumptions, Limitations, Caveats and Approximations


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 11.13

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

11.13 Allocation extraction of groundwater to urban water system

19.8.7 Groundwater allocation extraction–urban holder



Volume restated due to subsequent availability of actual meter readings

Change in line item name and number

In the 2010 Account, allocation extraction of groundwater from the Gingin bore field was estimated based on the allocation amount. Subsequent to the publication of the 2010 Account, measured extraction data were available for Gingin for the 2009–10 year. Because these data affected the allocation remaining volume (line item 3.8), the total volume of allocation extraction of groundwater was restated.