Sydney’s Tank Stream tour

Australia's oldest piece of European water infrastructure is still in service as a stormwater drain – and in demand as a tourist attraction.

The Tank Stream was built by First Fleet convicts and sits below what is now Sydney's CBD, running from Hyde Park and under Pitt St before flowing into Circular Quay.

“It hasn't been modified or changed because it's still very, very effective in getting water away from the city,” said Sydney Water Education and Community Partnerships Officer Louise Roberts.

The stream itself is a big part of why Sydney is where it is today, Roberts said.

“When Captain Arthur Phillip was deciding where to set up the first colonies he was looking for three things: a deep harbour so ships could come in close, arable land for farming and a good supply of fresh clean water,” Roberts said.

“He saw the stream and said it was the finest spring of water and decided that was where the settlement would be.”

But Phillip soon learned Australian streams did not run like European streams.

“When he arrived it was one of those very wet summers, so the water looked as though it was strong-flowing and consistent,” Roberts said.

“Then of course Sydney went into a drought – as Sydney does every five to 10 years – and they decided they'd better capture some of the water so they dug holes into the sandstone bedrock and created tanks to store the water.”

As part of Ozwater'17, Sydney Water will be offering tours of the site, which serves as a physical timeline of Australia's water infrastructure development.

“You go down into the 1960s concrete culvert build, then into a stone archway section built by stonemasons in the 1850s,” Roberts said.

“You get to see the sandstone floor that's been chipped by convicts to shape it so there's a better flow of water and some interesting engineering solutions. There's original expansion chambers and pipes that project water at a certain direction so that it doesn't cause any erosion to the sandstone.

“Then there's an 1870s oviform brickwork sewer that actually was designed in the United Kingdom, but we actually built the ones in Sydney before they built them in London.”

Sydney Living Museums is also running tours available to the public, but tickets are hard to come by, Roberts said. On average, 5500 people enter the annual ballot for only 160 tour places.

“A lot of people want to come because it's like a secret, hidden part of Sydney – it's something that you walk over the top of and you have no idea it's under your feet,” she said.

But for the industry, the Tank Stream means much more.

“It's really important to us [at Sydney Water] because its growth and development represents everything that we do for Sydney,” Roberts said.

“It was a drinking water supply and we've learned from the mistakes of the past and how to manage water better so we get safe and consistent supplies.

“Then it became a sewerage system and we've learned from that how to better manage hygiene and protect public health.

“And now it's part of our stormwater assets and is really important for flood mitigation in urban areas.”

Take a closer look at the Ozwater’17 program here.