For most of us, the modern world provides the convenience of a never-ending supply of clean and safe drinking water whenever we turn on a tap.
However, at the Australian Botanic Garden Mount Annan, the main water supply is principally derived from a very special water canal built in the 1880s, which is on the State Heritage Register.
The water source
WaterNSW's Upper Canal is a remarkable engineering feat, delivering water from four water supply dams to the south of the Garden (Cataract, Cordeaux, Nepean and Avon) to Prospect Reservoir in Sydney's west.
Currently, 20 per cent of Sydney’s drinking water travels through the Garden on a 64 km journey, dropping a mere 50 m elevation in all but 10 km of the canal’s length.
At times it can supply up to 40 per cent of Sydney's daily demand – an extraordinary feat considering it uses no energy other than the earth's gravity to transport water.
When the canal was was constructed more than 1,000 men were employed on the project and the entire length of the canal was dotted with tented construction camps. It is thought that the sandstone blocks were quarried from Mount Annan using horses - the only mode of transport at that time.
The canal is built from a variety of materials, depending on which stretch of land the water is passing through. Where the ground is soft, the canal is lined with unreinforced concrete slabs. In other sections, sandstone masonry is used, or the canal is cut directly into solid rock.
Interact sandstone and solid rock tunnels allow the canal to pass under the hills of Sydney. Aqueducts allow the canal to cross creeks and gullies – one of which is located in the Garden.
In all, the Upper Canal has one kilometre of aqueducts crossing nine creeks and the Southern railway line, nineteen kilometres of tunnels and 44 kilometres of open canal.