Adelaide
19.20 Other urban water system decreases

The volume reported (8,460 ML) represents decreases from the urban water system due to:

• water treatment plant (WTP) losses (5,325 ML)
• wastewater treatment plant (WWTP) losses (3,135 ML).

These losses are itemised in the following tables.

¹ Happy Valley inflow includes 61,070 ML of inflow from Happy Valley Reservoir and 3,820 ML of inflow from the Adelaide desalination plant (see note for line item 11.2 Entitled diversion of non-allocated surface water to urban water system).

² The calculation of metered inflow less metered outflow gave a negative value that was set to 0 ML (see 'Quantification approach').

^1-3 The calculation of metered inflow less metered outflow gave a negative value that was set to 0 ML (see 'Quantification approach').

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

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

During the 2011–12 year, the majority (66%) of Adelaide's urban water was sourced from catchments within the region (line item 11.2). Imported River Murray (line item 11.9) water constituted approximately 31% of the urban water supply system's source water. Also, during the 2011–12 year, the Adelaide desalination plant commenced operating and made up the remaining 3% of Adelaide's urban water sources (line item 11.6).

Urban potable water consumption (line item 19.4) was 127,729 ML during the 2011–12 year, representing 84% of all outflows from the urban water supply system. A very small volume of water (2%) was transferred out of the region via normal operations in SA Water's service area (line item 19.11). Non-revenue water, including pipes bursting and background leakage (line item 19.3) and other losses (line item 19.20), made up the remaining urban water supply system outflows.

The following figure shows all the inflows and outflows for 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 for Adelaide's urban water supply system during the 2011–12 year; line item numbers are provided in brackets

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

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

In the Adelaide region, wastewater is collected (line item 11.4) from users and treated by SA Water at one of their wastewater treatment plants.

During the 2011–12 year the majority (70%: line item 19.7) of treated wastewater was discharged to sea; approximately 25% was recycled (see recycled water system overview) and the remaining portion was discharged to surface water (2%: line item 19.5) or lost during wastewater treatment processes (3%: part of line item 19.20).

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. A small misbalance is shown and can be attributed to metering inaccuracies and unaccounted losses.

Note that volumes annotated with a * indicate flows between sub-components 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 for Adelaide's wastewater system during the 2011–12 year; line item numbers are provided in brackets

Readings may be from either the Supervisory Control and Data Acquisition (SCADA) database or manual field instrument readings, stored in the MetDaily file, SA Water WWTP records.

Metered inflow and outflow data for the seven WTPs listed in the following table were obtained from SA Water's SCADA database and/or MetDaily file for most of these WTPs. Inflow data were not available for the Barossa and Hope Valley WTPs. Barossa and Hope Valley WTP inflow was calculated from the respective WTP outflow, allowing for a 5% loss through the treatment process. Outflow data were not available for the Anstey Hill WTP. Instead, it was calculated assuming a 5% treatment process loss. The total process loss is the difference between WTP inflow and outflow.

The 2011–12 year inflow to and outflow from WWTPs within the Adelaide region were supplied by each WWTP. The data are measured by flow gauges that were manually read and recorded by plant operators. The WWTP loss was the difference between metered inflow and outflow. In case that difference was a negative, the loss was set to be 0 ML as a negative loss would mean that water was created during the treatment process, which is physically impossible.

• Volume of loss for the Onkaparinga Summit WTP is assumed to be 0 ML as metered outflow data exceeds metered inflow data.

• Volume does not include community wastewater management systems (CWMS) because the data were unavailable.
  
• Volume includes some wastewater collected from outside the Adelaide region and delivered to the Bird-in-Hand WWTP; however, this volume is negligible.
• For the Gumeracha, Hahndorf and Heathfield WWTPs 0 ML losses are assumed because only the outflows are measured, so inflow is assumed to be the same.
• Volumes of losses for the Christies Beach, Glenelg and Victor Harbour WWTPs are assumed to be 0 ML as metered outflows data exceed metered inflows data. 

This line item corresponds to line item 19.20 'Other urban water decreases' reported in the 2011 Account.

The volume of the line item for the 2010–11 year was restated from 7,747 ML in the 2011 Account to 7,993 ML in the 2012 Account as shown in the following table. In the 2011 Account, when the difference between metered inflows and metered outflows for the 2010–11 year was less than 0 ML, a negative volume was reported for process loss. As a negative loss is physically impossible, the error made in quantifying the line item volume for the 2010–11 year was corrected as shown in the following table.