Sydney
11.12 Entitled diversion of allocated surface water to urban water system

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 following tables provide a summary and breakdown of the allocation diversion of surface water by urban water utilities in the Sydney region.

The previous table is based on supply records of the bulk supplier, Sydney Catchment Authority; however, the water utilities, in the form of Goulburn Mulwaree Council, Shoalhaven City Council, Sydney Water Corporation, and Wingecarribee Shire Council, record differences in received volumes. The differences are attributed to different metering locations and metering accuracies and other unaccounted losses. In order to maintain consistency in calculations, the previous table, as well as the accounting statements, show the volumes recorded by the bulk supplier.

Diversions to the water treatment plants were measured at the plants. At the Goulburn Water Treatment Plant, inflow from the plant was measured using a flow meter.

The volume is based on metered data. Estimated accuracy based on meter accuracy and professional judgement is +/– 20%.

The flow diverted from Farmers Creek No. 2 Reservoir to Oakey Park water treatment plant was measured by the height of the water over the weir in the channel at the inlet works at the plant. There is a direct pipeline connection between the storage and the plant. The outflow from the water treatment plant was measured by an ABB Magflow meter.

The volume is based on measured data. Estimated uncertainty based on meter accuracy is +/– 2%. Meters are calibrated annually by their supplier, ABB.

An ABB Magmaster-type induction meter was used to measure flow data. 

The volume is based on metered data. Estimated accuracy based on meter accuracy is +/– 2%. Meters are calibrated annually by ABB (meter supplier).

Full-bore magnetic flow meters and ultrasonic flow meters were used to measure water diversions to urban utilities.

There are minor differences in the supplied volumes recorded by the Sydney Catchment Authority and its recipients. In order to maintain consistency, the values provided by the Sydney Catchment Authority have been used for this line item.

The volume is based on measured data. Estimated accuracy based on meter accuracy is +/– 2%.

Volumes were derived from ABB Magflow meter data received through the SCADA system and transferred into spreadsheets.

The quantification method used in this note only applies to the council's water diversions from Medway and Bundanoon storages to their respective water treatment plants. Supplies to the council's Wingecarribee Water Treatment Plant are made by the Sydney Catchment Authority.

The volume is based on measured data. Estimated accuracy based on meter accuracy is +/– 7%. External flow verification audits for the flow meters are conducted annually by Hydrometric Consulting Services.