Perth
3.1 Urban water supply system

This line item refers to the volume of water within the distribution pipe network and service reservoirs of the urban water system.

Water Corporation: Facilities Mapping System database.

Water Corporation.

The storage volume of the urban water supply system is comprised of two components: the distribution pipe network (5,750 ML) and the service reservoirs (1,253 ML).

The volume of water within the urban distribution pipe network was calculated using a geographic information system (GIS) layer of the pipe network. The attributes of the GIS layer were used to select trunk mains and pipes used for distribution and reticulation. Only those features that are actively used for the potable network were selected.

The total volume of water within the system was calculated by summing the volume of each section of pipe within the system. The volume of a section of pipe is the product of the length of the pipe section (km) by the cross-sectional area of the pipe (m²).

The volume of water within the service reservoirs of the urban supply system is measured on a daily basis at each reservoir. The total storage volume in these service reservoirs at the end of the 2010–11 year was that measured on 30 June 2011.

This value is an estimate of the volume of water within the supply system for the Perth metropolitan area. That is, it does not include water stored in the supply system for the southwest area (e.g. Mandurah).

It is assumed that all the pipes in the urban potable water supply system are at full capacity and have a uniform diameter. Unless the pipe network is augmented or partly decommissioned, it is likely that the volume within the pipe network will always be 5,750 ML.

It is estimated that the uncertainty about the storage volume within the service reservoirs is +/– 10%.

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 3.1

2011 Account line item	2010 Account line item	2011 Account volume at 30 June 2010 (ML)	2010 Account volume at 30 June 2010 (ML)	Change from the 2010 Account to the 2011 Account
3.1 Urban water supply system	5.1 Urban potable water supply system	6,942	6,942	Change in line item name and number