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Cotter catchment near corin dam

Cotter River Catchment

Cotter river

The Cotter River Catchment lies over 482 square kilometres within the ACT and the upper reaches of the Cotter River catchment are in the Namadgi National Park. The river itself starts high up the Brindabella Mountains, fed by rainfall and melting snow. The Cotter River Catchment is protected with no farms or houses and restrictions on recreation activities within the catchment also help to protect the quality of the water.

The quality of the water within the catchment suffered greatly during the January 2003 bushfires. A loss of vegetation immediately following the fires increased the amount of dirt and sediment entering the water meaning that water running off the catchment was more variable with increases in turbidity (cloudiness) as well increases in iron and manganese in the water. Since then, significant remediation works have been undertaken in the lower catchment to minimise these impacts.

There are three dams on the Cotter River: Corin, Bendora and Cotter. Corin Dam is located furthest upstream on the Cotter River. Water stored in Corin Dam is released downstream into the Cotter River and flows down to Bendora Dam. From Bendora Dam a large diameter pipeline carries water by gravity 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. The third dam, Cotter Dam is lower than the Mount Stromlo Water Treatment Plant, water from this reservoir must be pumped from the historic Cotter Pump Station, to the treatment plant.