Sydney

Volumes shown in the following table have been recorded as leakage from water distribution system to the landscape.

Data on leakage from water distribution system to the landscape are not available for the systems operated by other water authorities.

his line item comprises three different data-sets. The method for each data-set is shown below.

Note a: Shoalhaven City Council

Data source

NSW Water Supply and Sewerage: ‘Performance monitoring’ Report 2009–10. (Access through the ‘Performance monitoring’ webpage of the NSW Office of Water. The report will be included on the webpage from June 2011.)

Data provider

Shoalhaven City Council.

Method

The number provided by the council is the total loss and leakage from the urban potable water supply and nonpotable water (raw water diverted from the rivers) supply systems. This volume was estimated as 9% of the total consumption via the urban potable water and nonpotable water supplies.

Uncertainty

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

Approximations, assumptions, caveats/limitations

• 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 landscape water store, as the breakdown of leakage components entering landscape and groundwater stores are not available separately.

• The uncertainty estimate is based on the total leakage factor for the whole of the area managed, and may not specifically relate to the City Council area within the Sydney Subaccount Region (i.e. the value provided is likely to be an overestimate).

Note b: Sydney Water Corporation

Data source

Tables 12 and 13 of Sydney Water Corporation’s (SWC) Water conservation and recycling implementation report 2009–10.

Data provider

Sydney Water Corporation.

Method

SWC 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 (WTPs) with all known and estimated end uses. The remainder is classified as leakage.

Uncertainty

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.

Approximations, assumptions, caveats/limitations

• 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 landscape water store, as the breakdown of leakage components entering landscape and groundwater stores are not available separately.

Note c: Wingecarribee Shire Council

Data source

Data spreadsheets.

Data provider

Wingecarribee Shire Council.

Method

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 WTPs are configured with the consumption figures obtained by flow meter readings at listed properties.

Uncertainty

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

Approximations, assumptions, caveats/limitations

• 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 landscape water store, as the breakdown of leakage components entering landscape and groundwater stores are not available separately.