Water treatment

Historically ActewAGL provides around or more than 100 million litres of treated water each day to Canberra residents and Queanbeyan City Council. Most of the water required to meet Canberra’s and Queanbeyan’s needs is drawn from the Cotter River catchment, with water from Googong being drawn to meet peaks in demand in summer or during extensive dry periods. Since the drought, water has been drawn from Googong more frequently, as well as from the Murrumbidgee River.

Water from the Cotter River catchment and Murrumbidgee River is then treated at Mount Stromlo water treatment plant, while water from Googong dam is treated at the water treatment plant adjacent to the Googong dam.

The Cotter River catchment

The Cotter River catchment upper reaches are part of Namadgi National Park and the catchment lies within the borders of the ACT. The river itself starts high up on the Brindabella Mountains and is fed by melting snow and rainfall. Corin, Bendora and Cotter dams are part of the Cotter River catchment, which are heavily protected from outside activities that may affect water quality.

The water from this catchment is of good quality, although the catchment suffered severe damage during the January 2003 bushfires. The loss of vegetation in the catchment means that the quality of water running off the catchment is more variable. Immediately after the fires, there was an increase in the turbidity (cloudiness) and associated iron and manganese in the water flowing into the three Cotter River reservoirs.

Water stored in the highest dam, Corin, is released into the Cotter River to add to the level of storage in Bendora dam. From Bendora, a large diameter pipeline brings the water by gravity flow to the treatment plant on Mount Stromlo to the west of Canberra. The Bendora gravity main is 20 kilometres long and has the capacity to carry 310 million litres of water per day.

In December 2004 the Cotter dam was brought online in response to the ongoing drought. The water from the Cotter dam had not been used in recent prior years and was held as a drought reserve. Water from the Cotter dam is pumped to the Mount Stromlo water treatment plant, blended with water from Bendora supply, and treated for supply to Canberra.

The Queanbeyan River catchment

Canberra’s water supply system also includes the Googong dam on the Queanbeyan River to the southeast of Queanbeyan. As Googong dam is in an occupied rural catchment which includes farmlands and small communities, the water quality from this catchment can be variable and requires extensive treatment.

Murrumbidgee River

The use of water from the Murrumbidgee River commenced in May 2007 from a location near the Cotter Pumping Station as an additional water supply to the ACT's depleted water storages.

The Murrumbidgee River is one of Australia's major rivers and many communities use it as their water source. For decades, major towns upstream and downstream of Canberra, such as Cooma and Wagga Wagga, have drawn water from the Murrumbidgee River, treated and safely used it for drinking.

Many of the world’s great rivers are used to provide drinking water, such as the Thames River in the UK, the Colorado River in the US and the Rhine River in Germany. Detailed health and scientific studies have shown that with appropriate treatment, water from such sources is safe to drink.

Mount Stromlo Water Treatment Plant

The original Mount Stromlo water treatment plant (WTP) was commissioned in June 1967. It contained facilities for chlorination, fluoridation and pH correction of all water drawn from the Cotter system.
More about Mount Stromlo WTP.

Googong Water Treatment Plant

The Googong Water Treatment Plant (WTP) was built in 1979 at the same time as Googong dam.

The Queanbeyan River catchment, which feeds Googong dam, is an occupied rural catchment, and extensive treatment is necessary to ensure a safe water supply. Recreational activities on Googong dam are controlled to avoid excessive turbidity and contamination problems.
More about Googong WTP.