Sunday 3 January 2016

Sydney Water Supply Upper Canal, NSW

Sydney Water Supply Upper Canal

Mount Annan/Currans Hill/Catherine Field/Leppington
Camden LGA, NSW

Upper Canal built in the 1880s  (WaterNSW)

History and Description

The Upper Canal is an engineering marvel and is entirely gravity fed. It is probably the most important engineering heritage item in the Camden LGA.

In 1867, the growth of Sydney coupled with recurring dry seasons, brought into sharp focus the pressing need for a water supply, which was larger and more reliable than the existing Botany Swamps source. This lead the Governor (Sir John Young) to appoint a special Commission to investigate how an adequate long term supply might be achieved. (SHI)

The Water Supply Canal consists of tunnels, open canals and aqueducts that convey water 62 km from Pheasants Nest to Prospect Reservoir, entirely by gravity. The canal passes under part of the Australian Botanic Garden at Mount Annan via a 686 metre tunnel.  (ABG, Mount Annan)

When the Upper Nepean Scheme was commissioned in 1888, it diverted water (which previously would have flowed down the lower stretches of the Nepean River to Camden and Penrith) into the Upper Canal, by means of which it was conveyed to Prospect Reservoir and thence to Sydney

The Upper Canal was built between 1880-88 after more than a decade of investigation into schemes to provide Sydney's fourth source of water supply.

The Camden Water Supply Works were completed and officially opened in November 1899, rating commencing from 1st January 1900.

This scheme, first proposed in 1869, harnessed the headwaters of the Nepean River and its tributaries, the Cataract, Cordeaux and Avon Rivers, to ensure a reliable, high-quality water supply for the rapidly growing city. (State Heritage Inventory)

The canal provides water for Camden, Campbelltown and Liverpool, also Wilton, Appin and Douglas Park. Until 1960 when the Warragamba Dam was completed, the Upper Nepean system supplied most of Sydney's water. It is a remarkable engineering feat which will continue to supply this most precious resource for many years to come.

The Sydney Water Supply Canal is managed by the Sydney Catchment Authority. It runs through the centre of the Australian Botanic Garden and supplies most of the irrigation water for the Garden.

The canal is mainly cut through natural sandstone bedrock but some sections, especially where it passes through shale, are lined with sandstone, brick or cement. It is believed that sandstone quarried from the north face of Mount Annan was used for this purpose and as capping on the brick aqueduct south of the tunnel. (Australian Botanic Gardens, Mount Annan)

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.(WaterNSW)

Condition and Use

The canal is in good condition. (SHI)

Apart from the decommissioning of the Lower Canal, which nonetheless still remains a distinct entity, the whole of the Upper Nepean Scheme remains largely intact and performs the same functions as originally intended. (SHI)

Heritage Significance

An early water supply canal built 1880-1888 and still in use today. (SHI)

It has functioned as a unique part of the main water supply system for Sydney for over 120 years, and apart from development in supply and improvements has changed little in its basic principles since the day it was completed, except for the decommissioning of the Lower Canal in the 1990s (now owned by Department of Environment, Climate Change and Water).

It provides detailed and varied evidence of engineering construction techniques prior to the revolution inspired by reinforced concrete construction. Although concrete was later used to improve the durability of the System, much of the earlier technology is still evident along the Canal.

The scheme possesses many elements of infrastructure which are of world and national renown in technological and engineering terms. (SHI)

Heritage Listing

Camden LEP Item I122
State Heritage Inventory
State Heritage Register Listing No 4580004

Read More

State Heritage Inventory Click here
The Upper Canal - WaterNSW Click here
125 Years of the Upper Nepean Scheme Click here
The Upper Nepean Scheme on Wikipedia Click here
Engineers Australia and Prospect Reservoir Click here
Camden Heritage List Click here