Published on 12 August 2020

Exploring the Clarendon Weir

There's a lot to discover about the historical Clarendon Weir.

For 125 years, the Clarendon Weir has played a significant role in managing the supply of water to homes and businesses across metropolitan Adelaide.

The Clarendon Weir project was proposed by a Royal Commission in 1888 in response to the increased consumption of water in Adelaide. After the project was passed by the Onkaparinga Waterworks Act 1891, construction of the weir on the Onkaparinga River began in July 1892. A labour force of more than 360 men took four years to complete the project.

The weir wall was constructed to a height of 14 metres using approximately 2700 tonnes of marble stone, quarried from Macclesfield in the Adelaide Hills. Each of the solid marble blocks weighed more than six tonnes. The terraces are also made of large marble pieces. The weir includes more than 1000 tonnes of concrete from Brighton Cement Works.

The weir was completed in August 1896 and ceremoniously opened by then Governor of South Australia Sir Thomas Buxton. To add to the beauty of the weir and its surrounds, a conservator of forests named Mr Gill planted willows, flowering gums, pines, silver beeches and other exotic trees. Many of these trees are still thriving in the area today.

The weir was an engineering feat of its time, representing a significant achievement in the engineering capacity of South Australia,” says Kelly Dyer, council’s library officer specialising in local history.

“The new weir and tunnel were quite the tourist attractions while under construction and afterwards, with many visitors enjoying picnics nearby.”

The weir’s purpose is essentially to dam the Onkaparinga River and divert water to Happy Valley Reservoir.

The Clarendon Weir pools water from Mount Bold Reservoir which releases the water, as required, to maintain an adequate level at the weir. From there, a five-kilometre long inlet tunnel is used to carry the water to Happy Valley Reservoir where it’s treated before being supplied to approximately 500,000 homes and businesses. At the time of construction, the tunnel was thought to be the longest ever built in Australia.

In times of flood, the weir helps to control the flow of water as needed. The tower at the southern end houses chambers and apparatus for working the sluice gates. Inside the northern tower, valves discharge the water into a cemented culvert, which feeds into the pipes.

“The Riverbend Reserve, on Nicolle Road, is a great spot for people to park and enjoy a walk around the vicinity of the weir,” Kelly says. “In winter and springtime, if we’ve enjoyed heavier rainfalls, the water gushing over the weir is a sight to behold.”


A view of the stunning Clarendon Weir.