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

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

• Urban water supply system
• Wastewater system
• Recycled water system.

There are two main sources of water for Sydney's urban water supply system:

• surface water (11.12)
• desalinated water (11.6).

Urban water consumption (19.4) was 489,557 ML during the 2011–12 year, representing 48% of all urban water supply system outflows. The remaining urban water was reported as being lost through leakage to landscape (19.2) and operational losses (19.20).

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.

The Sydney region's urban water supply system using data from Sydney Water Corporation, Shoalhaven City Council and Wingecarribee Shire Council

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 receivers, in the form of the Shoalhaven City Council, Sydney Water Corporation and Wingecarribee Shire Council, record differences in received volumes. The differences are attributed to limits in meter accuracy. 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 WTP, 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 judgment 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 WTP 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 metered outflow data from WTPs.

The flow meter data are continually monitored and recorded using IICATS. The data are stored within a complex data management system. Adjustments are made to the data (if necessary) to correct any interruptions, errors and so on. Data have been extracted for 2010–11 from the data management system.

As data on inflow to each WTP are not available, metered outflow is assumed to be equal to the surface water taken. The volume taken from surface water can be higher than the outflow volume due to losses associated with pipe systems and the filtration process.

This line item applies to Sydney Water Corporation only for its water diversions from the Hawkesbury River to North Richmond WTP. All the other supplies to Sydney Water Corporation are made by the Sydney Catchment Authority.

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 WTPs. Supplies to the council's Wingecarribee WTP 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.

In the 2010–11 year, diversions made by urban entitlement holders was incorrectly stated in 17.11 Entitled diversion of allocated surface water to users. These include diversions made by Goulburn Mulwaree Council, Palerang City Council's and Sydney Water Corporations totaling 5,768 ML. As these water rights are held for the urban water store, the diversion is now recognised under 17.12 Entitled diversion of allocated surface water to urban water system. Consequently, the value for this line item has been restated from 438,169 ML to 443,937 ML.