Canberra
19.5 Discharge from urban water system to surface water

The volume reported in the water accounting statements (34,325 ML) represents the total volume of water discharged from the urban water system to surface water within the Canberra region during the 2011–12 year.

The total wastewater volume collected was 38,429 ML during the 2011–12 year. Approximately 88% of the collected wastewater discharged to surface water after treatment (34,325 ML).

During the 2011–12 year, approximately 11% of treated wastewater was recycled; and the rest was the losses. The following figure shows all the inflows and outflows associated with the wastewater system.

For more detail on a particular flow associated with the recycled water system, refer to the line item notes. Note that volumes annotated with an * 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 during the 2011–12 year for Canberra's wastewater system. Line item numbers are provided in brackets.

This line item is made up of several components. When capacity is available, treated water is transferred from Mount Stromlo Water Treatment Plant (WTP) into Googong Reservoir via the water reticulation network. In addition to this there are two wastewater treatment plants (WWTPs) within the Canberra region that discharge treated water into the Molonglo River: the Lower Molonglo Water Quality Control Centre (LMWQCC) upstream from the confluence with the Murrumbidgee, and the Queanbeyan WWTP upstream of Lake Burley Griffin and Uriarra WWTP.

The table below contains a breakdown of the volume of water discharge to surface water at each wastewater treatment plant and the volume of water transferred to the Googong reservoir.

The table above provides a breakdown of the volume of wastewater discharge to surface water at each WWTP in the Canberra region for the 2011–12 reporting period. Only the LMWQCC, Uriarra WWTP and the Queanbeyan WWTP discharge treated wastewater to the surface water store. The volume reported for LMWQCC includes 670 ML which spilled from storage dams prior to treatment in the 2011–12 year.

Under the urban water utility water access entitlement, ACTEW abstracts water from the regulated storages of Bendora and Cotter reservoirs, and the unregulated system of the Murrumbidgee River and transfers this water to Mount Stromlo WTP. If capacity is available, it is also possible to transfer treated water from Mount Stromlo WTP into Googong Reservoir via the water reticulation network.

ACTEW Water's flow meter measures the release from the water distribution system to Googong Reservoir.

Nil.

Derived from measured data. Estimated uncertainty is +/– 5%.

ACTEW Water's flow meter measures the release from the water distribution system to Googong Reservoir.

Nil.

Derived from measured data. Estimated uncertainty is +/– 5%.

Treated wastewater discharged to the surface water store was measured by WWTP outflow flow meters. The 2011–12 discharge volume was extracted from the QCC database. The Queanbeyan WWTP is the only QCC WWTP that discharges treated wastewater to the surface water store.

Nil.

Derived from measured data. Estimated uncertainty is +/– 5%.

This line item corresponds to line item 19.5 'Urban water discharge to surface water' reported in the 2011 Account.