Sydney
19.20 Other urban water system decreases

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 wastewater 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.

The Sydney region has several urban utilities responsible for managing wastewater in the region. Sydney Water Corporation, Shoalhaven City Council, Goulburn Mulwaree Council, Lithgow City Council, and Wingecarribee Shire Council all collect wastewater from users (11.4 Wastewater collected) and treat this wastewater at a number of wastewater treatment plants throughout the region.

During the 2012–13 year, a total of 507,638 ML was collected by the wastewater system. The majority of the outflow from the wastewater system (around 77%) was discharged to the sea (19.7 Wastewater discharge outside of region); around 10% was discharged to inland surface water (19.5 Urban water discharge to surface water) and a further 10% of that wastewater was recycled and the remainder was losses from the system (see 19.1 Evaporation from urban water system and 19.20 Other urban water decreases). The following figure shows all the inflows and outflows associated with the wastewater system.

For more detail on a particular flow associated with the wastewater system, refer to the line item notes. Note that volumes annotated with an asterisk (*) indicate flows between subcomponents and are not reported in the account. As such, these flows do not have an associated line item number.

Schematic diagram of water inflows and outflows during the 2012–13 year for Sydney's wastewater system; line item numbers are provided in brackets

Supporting information

The volume of 30,657 ML calculated for this line item reports on the remaining non-revenue water (losses) from the urban water supply system and losses from the wastewater system. 

The remaining non-revenue water volume reported in this line item includes the losses other than those reported in 19.1 Evaporation from urban water system and 19.3 Leakage to groundwater. The wastewater losses reported  as part of this line item includes the modelled network wet weather overflows and wastewater outflows to sea prior to treatment as reported by Sydney Water Corporation.

A breakdown of the total volumes reported in this line item is provided in the table below. Further breakdowns of these volumes are available in each of the individual quantification notes.

Breakdown table of other urban water system decreases for the Sydney region in the 2012–13 year

Loss type	Water authority	Volume (ML)
non-revenue potable water other than pipe bursts and leakage	Sydney Water Corporation	15,166
	Shoalhaven City Council	31
	Wingecarribee Shire Council	25
	Goulburn Mulwaree Council	464
other wastewater losses	Sydney Water Corporation	14,971
Total		30,657

Goulburn Mulwaree Council databases.

Goulburn Mulwaree Council.

The other non-revenue component is calculated according to the table below.

Calculation method for other non-revenue potable water for Golbourn Mulwaree Council

		Volume (ML)
	volume taken from surface water for treatment (11.12 Allocation diversion of surface water to urban water system)	2,769
less	leakage to groundwater (19.3 Leakage to groundwater)	13
less	potable consumption (19.4 Delivery to urban water users)	2,292
equals	other urban water system decreases	464

 

The difference between the volume of surface water diverted by Goulburn Mulwaree Council and leakage and urban use is assumed to be the non-revenue component.

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

New South Wales Office of Water calculations.

Shoalhaven City Council.

A leakage value is derived by a calculation of the total water treated less authorised potable supply (line item 19.4 Delivery to urban water system users). The New South Wales Office of Water will make adjustments if the calculation produces a figure that is outside a specified percentage of total water supplied.

Nil.

Estimated uncertainty, based on meter accuracy and professional judgement on determination of boundaries of water supply areas beyond the Sydney region, 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.

Breakdown of other urban water system losses reported by Sydney Water Corporation

Type of loss		Volume (ML)
non-revenue potable water	customer meter under registration	9,245
	unauthorised consumption	515
	unbilled metered consumption	219
	unbilled unmetered consumption	5,187
wastewater system losses	modelled network wet weather outflows	13,858
	untreated discharge to sea	1,113
Total		30,137

Nil.

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 judgment and organisational practice is +/– 20%.

Other losses reported in this line item in the 2012 Account included non-revenue water reported from Shoalhaven City Council and non-revenue water and pipe bursts reported by Wingecarribee Sire Council. As pipe bursts are accounted for in line item 19.3 Leakage to groundwater, the volume of 283 ML reported in the 2012 Account as pipe bursts is now restated in this line item. The volume reported for '19.20 Other urban water system decreases' has now been restated as 164 ML.