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The Upper Canal - an unsung hero of Sydney’s history

The Upper Canal - an unsung hero of Sydney’s history

A505-1167

The Upper Canal.

The Upper Canal is an unsung hero of Sydney's history. A precise piece of engineering still serving the needs of Sydney 130 years later.  Built in the 1880s, now listed on the State Heritage Register, the Upper Canal is still the only way of transferring water to Sydney from the four Upper Nepean dams (Cataract, Cordeaux, Avon and Nepean).

These dams supply on average 20 per cent of Sydney's water, but at times can supply up to 40 percent of Sydney's daily demand.  'Green' before its time, it uses no energy other than the earth's gravity to transport water 64 kilometres to Prospect Reservoir in Sydney's west.

The canal drops just 50 metres in elevation over 54 kilometres after the Nepean and Cataract tunnels - just 0.1 percent grade - a marvellous feat of engineering following the earth's contours.

The canal is built from a variety of materials, depending on the nature of the country it passes through. Where the ground is soft, the canal is trapezoidal in shape and the sides lined with unreinforced concrete slabs. In other sections, the canal is u-shaped and the sides are lined with sandstone masonry. Where the canal is cut into solid rock, it is unlined.

Tunnels allow the canal to pass under hills. These are unlined if cut through solid rock, or lined with brick or sandstone if cut through softer material.  Aqueducts allow the canal to cross creeks and gullies. These were inverted iron syphons resting on sandstone piers.

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.

Many of the original iron pipes remain in use, some lined with plastic sleeves to protect the pipes and keep them waterproof.  Many of the original mechanisms to control and divert the water's flow - such as stop logs, penstocks, and gate valves - are also still in use.

61.0
Monday 19 November
-0.5
1,574,616 ML
2,581,850 ML
11,104 ML
1,587 ML
-11,906 ML
Monday 19 November