Sydney
19.3 Urban water system leakage to groundwater

The urban water supply system is one of three subcomponents of Sydney's urban water system. The three subcomponents are the:

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

In the 2012–13 year, all water supplied to the urban water supply system was sourced from surface water (11.12 Allocation diversion of surface water to urban water system) with a small volume of 596 ML sourced from the Fish River Water Supply Scheme by Lithgow City Council (11.9 Delivery of water to urban water system under inter-region agreement). Sydney Water Corporation in the past has also sourced water from desalinated water (11.6 Delivery of desalinated water to urban water system); however, no desalinated water was reported this year.

Potable and nonpotable urban water consumption (part of 19.4 Delivery to urban water system users) was 472,541 ML during the 2012–13 year, representing 88% of all urban water supply system outflows.The remaining outflows are reported as being lost through leakage (19.3 Leakage to groundwater) as well as other operational losses (19.20 Other urban water decreases), and a small volume was exported outside the region (19.11 Transfer of water outside of region).

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 Sydney's urban water supply system; line item numbers are provided in brackets

The volume of 44,899 ML reported in this line item represents the total leakage from the urban water system to the groundwater. This line item includes some of the non-revenue water associated with urban water supplies; remaining non-revenue water is reported in line item 19.20 Other urban water decreases.

A breakdown of losses reported by each organisation is available below.

Leakage volumes reported by each urban water supplier for the 2012–13 year

Water authority	Volume (ML)
Sydney Water Corporation	43,792
Shoalhaven City Council	324
Wingecarribbee Shire Council	770
Goulburn Mulwaree Council	13
Total	44,899

Data spreadsheets.

Goulburn Mulwaree Council.

Volume of background leakage estimated at wastewater treatment plants.

Nil.

Volume is estimated. Uncertainty based at + / – 10%.

New South Wales Water Supply and Sewerage Performance Monitoring Report.

Shoalhaven City Council.

Shoalhaven City Council determines leakage through the reconciliation of water treated and the recorded consumption and estimated end uses. The remaining figure is recorded as leakage.

Nil.

The volume is based on measured data from a sample area and extrapolated to other areas. Estimated uncertainty based on meter accuracy, professional judgement and organisational practice is +/– 5%.

Water Efficiency Report 2012–13.

Sydney Water Corporation.

Sydney Water Corporation used the global water balance approach to determine leakage and loss from the potable water supply system. The water balance is a reconciliation of the volume of water produced by the water treatment plants with all known and estimated end uses. The remainder is classified as leakage.

• Data represents total leakage and loss from potable and nonpotable water supply systems, as the breakdown between the two supplies is not available.
• Total volume of estimated loss and leakage from the urban water supply system is to be taken as an input to the groundwater store, as the breakdown of leakage components entering landscape and groundwater stores are not available separately.

Measured and estimated data used in the water balance for the calculation contribute to uncertainty of leakage volumes. As leakage volumes calculated via a water balance are proportionally small, residual errors tend to be magnified. The uncertainty band on leakage as calculated by an annual water balance is estimated to be about +/– 25% with a 95% confidence limit.

Data spreadsheets.

Wingecarribee Shire Council.

The value represents the total volume of leakage and losses from the potable water supply system. The volume is based on the water balance method, where potable water production figures from the water treatment plants are configured with the consumption figures obtained by flow meter readings at listed properties.

• Data represents total leakage and loss from potable and nonpotable water supply systems, as the breakdown between the two supplies is not available.
• Total volume of leakage is based on an estimated 11% loss from the system.

The volume is based on measured data. Estimated uncertainty based on meter accuracy, professional judgement, and organisational practice is +/– 20%.

The volume reported in this line item for the 2012 Account has been restated as 43,270 ML. This is the sum of the volumes previously reported in line item 19.2 Leakage to landscape, plus those reported as pipe bursts in line item 19.20 Other urban water decreases.