ACT and Queanbeyan water storage – dams

Cotter Dam was constructed in 1912 to serve the needs of the Canberra people during the establishment years. Water was pumped from C otter Dam to Mount Stromlo, where it flowed by gravity to service reservoirs. The height of the dam was increased in 1951 to meet the needs of Canberra's growing population. In the 1950s the Cotter storage could not hold enough water to cope with a drought, and a second dam further up the Cotter River was built.

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.

• Location: Cotter River
• Storage Capacity: 3,856 million litres* fed from a 482 square kilometre catchment area which also contains the Bendora and Corin Dams.
• Top water level: 500.69m above sea level
• Facts: Cotter Dam is a concrete gravity dam built in 1912 (height raised in 1951). Cotter Dam was not used for water supply for many years as Bendora and Corin Dams usually have better water quality. In December 2004 ActewAGL brought the Cotter Dam online in response to the ongoing drought.

Bendora Dam was finished in 1961 and, as it was higher, water could now flow by gravity to Mount Stromlo Water Treatment Plant (WTP), avoiding the high cost of pumping. The Bendora gravity main was constructed in 1967.

• Location: Cotter River
• Storage Capacity: 11,540 million litres* fed from a 290 square kilometre catchment.
• Top water level: 778.2m above sea level
• Facts: Double curvature concrete arch dam, Bendora dam was completed in 1961.

Water stored in the highest dam, Corin, is released into the Cotter River to raise the level of storage in Bendora Dam. From Bendora a 1500mm diameter steel main brings the water by gravity flow to the treatment plant on Mount Stromlo to the western of Canberra. The Bendora gravity main, constructed in 1967, is 20 kilometres long and has a capacity to carry 310 million litres of water per day.

A third dam, Corin Dam, was completed in 1968. Water stored in Corin, the highest dam in the Cotter River system, is released into the Cotter River thereby controlling the level of storage in Bendora Dam.

• Location: Cotter River
• Storage Capacity: 70,900 million litres* fed from a 197 square kilometre catchment area
• Top water level: 955.54m above sea level
• Facts: Corin Dam is an earth and rockfill embankment dam with side channel spillway, completed in 1968.

Population projections showed that by 1979 the Cotter River system would not be able to cope with the demand for water. A new dam was required and, after extensive investigations, a site was selected on the Queanbeyan River. Googong Dam was constructed.

• Location: Queanbeyan River
• Storage Capacity: 121,083 million litres* fed from a 873 square kilometre catchment area.
• Top water level: 663.0m above sea level
• Facts: An earth and rockfill embankment dam with adjoining converging chute spillway and nearby 13 metre high earthfill saddle embankment. It was completed in 1979.