South East Queensland
19.3 Urban water system leakage to groundwater

The volumetric value for the line item at the end of the 2012–13 year was 27,613 ML.

This line item represents the background leakage from the urban water system to groundwater. The volume presented is the combined volume of the pipe bursts and background leakage from the urban water supply system due to the lack of data to separate the pipe bursts and background leakage components.

South East Queensland's (SEQ) urban water system comprises three sub-components: 

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

There are four main sources of water for SEQ's urban water supply system:

• surface water (11.2 and 11.12 )
• groundwater (11.3)
• desalinated water (11.6)
• imported water (11.5). 

The water intake to the urban water supply system (251,897 ML) is from four sources: surface water (224,420 ML), groundwater (158 ML), desalinated water (2,805 ML), and imported water (24,514 ML).

During the 2012–13 year, the volume of water delivered to urban users (potable and non-potable water supplied amounting to 219,392 ML) was the major outflow from the urban water supply system. This supply for urban consumption represented about 87% of the total outflow. Approximately 11% of the outflow was leakage (19.3 Urban water system leakage to groundwater) and 2% was remaining losses.

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

Background leakage and pipe bursts:

Seqwater; Queensland Urban Utilities; Unitywater; Redland City Council; Council of the City of Gold Coast; Toowoomba Regional Council 

Seqwater; Queensland Urban Utilities; Unitywater; Redland City Council; Council of the City of Gold Coast; Toowoomba Regional Council.

The volume of (bulk) leakage reported by Seqwater was deduced from the previously published average of 1.269 ML/day for the whole SEQ bulk network . This figure is due to be reviewed by SEQ Water and a project is currently underway.

This line item also includes the combined volume of background leakage and pipe bursts from the urban water supply system (real losses component of the non-revenue water) reported by the urban water authorities. Non-revenue water is generally calculated as the volume of water supplied to users less metered and billed domestic and non-domestic water consumption. Non-revenue water may be broken into four components: authorised unbilled, apparent losses (unauthorised), apparent losses (metering), and real losses (bursts, leaks and background losses). The non-revenue water components other than the real losses (identified as non-revenue water remaining) are presented as part of line Item 19.20 Other urban water decreases.

No information on the volume of water lost due to pipe bursts was available to separate that component from the total volume reported as leakage to groundwater. It is assumed that the over-estimation of the volume of leakage to groundwater due to inclusion of the losses due to pipe-bursts would be minor.

Leakage volume presented as part of this line item may be an over-estimation where the volumes reported are applicable for the total area served by a water authority part of which extends outside the National Water Account SEQ region boundary.  This over-estimation is assumed to be minor.

Estimated in the range +/– 30%.

This line item corresponds to line item 19.3 'Leakage to groundwater' reported in the 2012 Account.