Dams of the Upper Nepean River

The Upper Nepean Scheme was commenced in 1880 after it was realised that the Botany Scheme was insufficient to meet Sydney's water supply needs. The Nepean project consisted of the construction of a weir across the Nepean River to divert of the rivers, Cataract, Cordeaux, Avon and Nepean, to the Prospect Reservoir. These dams have provided the majority of Sydney's water requirements from the turn of the 20th Century. All are easily accessible by car and facilities have been provided at all locations for visitors seeking to use the dams and the landscaped areas around them for recreational purposes. Apart from Warragamba Dam, all are approached from Sydney via Campbelltown. No direct access by public transport.

The Upper Nepean catchment covers almost 900 square kilometres of mostly pristine bushland on the Illawarra Plateau south of Sydney. Its tall forests, swamps and rainforests are home to many rare and threatened species, including the white waratah. The catchment lies at the southern end of the Illawarra Plateau, which stretches from Robertson north to Heathcote National Park, and is bordered by the Illawarra escarpment in the east, Campbelltown in the north-west and the villages of Bargo and Yerrinbool in the south-west.

Protected from most human activities for over 130 years, the area is a haven for the spotted-tail quoll, giant burrowing frog, flame robin, swift parrot and sooty owl. The catchment is also the home to the white waratah. Like the Wollemi Pine, the exact location of the white waratah, discovered in the 1960s, has been kept secret for its protection. Most of all white waratahs available today have their ancestor in this one plant.

Cataract Dam

Construction of the Cataract Dam was the major step towards the ultimate provision of a reliable water supply for Sydney. It is the first of the major water supply dams to be built in Australia, being larger than both of the earlier Avon and Nepean Dams. The dam was a testing ground for engineering innovation and structural technology, being the first water storage apparatus constructed within Australia to utilise the cyclopean masonry civil engineering technique. Further to this, the building team made extensive use of electricity as a powerful new construction tool, and used production line techniques for the quarrying of stone blocks for the first time.

The dam is built of cyclopean masonry, composed of sandstone blocks weighing from two to four and a half tons. These were quarried at the site and bedded in cement mortar. The vertical joints were filled with basalt or sandstone concrete. The upstream face consisted of basalt concrete moulded blocks set in a cement mortar. The downstream face was of basalt concrete, 1.8m thick in the lower section and 0.9m thick in the upper section. There were two lines of 122 cm diameter pipes which passed through the dam and discharged water into the river. The flow is controlled by a Larner Johnson Needle valve. The upstream parapet was castellated with sandstone blocks while the top of the downstream wall was corbelled in concrete. The water from Cataract is discharged into the Cataract River downstream to Broughton s Pass. From here it is diverted into the Cataract tunnel, the first of the Upper Canal structures by which it is conveyed to Prospect reservoir.

The total cost of construction of the dam was £329,136. The reservoir was filled to capacity for the first time on 13 January 1911. However, it was realised that the spillway should be widened to avoid the risk of floodwaters over topping the wall. This work was completed in 1915. Cataract Dam presently serves the suburbs to the west of Sydney and those of Wollongong, and remains a symbol of engineering innovation at the turn of the century. It provides a venue for passive recreation within the cartilage of the dam and its immediate surrounding catchment. The public area surrounding the dam is maintained and a large picnic area, shelter sheds, fireplaces and playground area are provided amongst attractive gardens. The site contains many intact elements of the early 20th century landscape design scheme.
Cordeaux Dam

The Cordeaux Dam was the second major storage dam built during the second stage of the Upper Nepean Water Supply Scheme. An arched dam, it is primarily composed of cyclopean masonry consisting of sandstone blocks quarried from the site and embedded in concrete. Each end of the Dam wall is flanked by sandstone pylons in the Federation Egyptian style, of giant scale. These are adorned with a decorative motif (lotus columns) and contribute to overall aesthetic.

The upstream face consists of hard basaltic stone, used in preference to softer sandstone, 0.6m thick, merging into sandstone concrete 1.8m in width at lower levels and 1.2m at higher levels. The downstream face consists of sandstone concrete 1.2m thick. Most of the plant machinery on the dam site was operated electronically, and the current was supplied from the State Power Station at Port Kembla by transmission lines 22.5 km in length. Cordeaux Dam currently stores water for the South Coast and Wollongong regions.

The Cordeaux Dam site is a popular tourist attraction. The public area is maintained with picnic grounds, landscaped gardens, shelter sheds and pathways. The grounds associated with the main public areas of the dam contain many intact landscape elements from the circa 1930s (and possibly late 1920s).

The public picnic grounds and gardens attached to the Cordeaux Dam contain a cultural landscape resource  including remnants of its interwar period plantings, layout and detailing, and extensive areas of bushland. There is evidence in the landscape design, particularly in the use of palms and tree ferns and battered stonework retaining walls, of an intention to continue the Egyptian Revival references apparent in the design of the main dam structures.
Avon Dam

Avon Dam was the third and largest of the four water supply dams built in the development of the Upper Nepean Water Supply Scheme. Designed to impound a huge volume of water, it was large by international standards of the time. The dam remains the second largest in the Sydney water supply system. Like the others in the Nepean Scheme, it is valued aesthetically for the fine execution of its decorative Egyptian pylons which flank the entrances to the dam wall.

The dam wall is curved in plan and has a spillway channel constructed as an open cut through a ridge between the Reservoir and a watercourse. It discharges into the Avon River approximately 0.8 km below the dam. In 1971, work was commenced in order to alleviate uplift pressure and leakage through the foundations of the dam wall. This was carried out in accordance with modern design and engineering techniques, involving the support of the downstream face of the wall with an embankment of quarried sandstone blocks and sandstone fill, the latter being compacted by grid and vibratory rollers. The spillway was also modified from the original 1.2 m high mass concrete weir, and transformed into a sawtooth shape. Work on the dam commenced in 1921. It was completed in 1927 and handed over to the Water Board in 1928.

The Dam currently serves the Wollongong area. An electrical pumping station located at Flying Fox Creek, facilitates the transfer of water over the Great Dividing Range to the Wollongong and Shell Harbour areas. The Dam today has a well-developed picnic area on its eastern side, approximately in the area formerly occupied by the construction village. This picnic area features landscaped gardens within picturesque retaining walls, large areas of lawn and modern amenities and shelter facilities. There is a large rivetted steel (possibly cast-iron) elevated water tank within the picnic area, carried on rivetted plate-web girders and cast steel (or iron) posts. There is only one early residential building remaining, believed to be the former Resident Engineers residence. It is a single-storey weatherboard building with terracotta tiled hipped roof which also has a breakfront gabled wing.

After the immediate dam environment of the Cataract Dam, that of the Avon Dam is perhaps the most scenically impressive landscape. Near the dam wall there are several distinct gardens that function as individual picnic areas. These include a series of grotto-like shelters along the sandstone cliff that defines the western edge of the area; a discrete palm-planted area with ornamental pools; and a larger park-like area extending to the south along the edge of the dam. A pool garden is dominated by four large circular ponds, with small intermediate ponds. The larger ponds even have their own planters attached to the sides. The ponds are surrounded by an array of palm and Cordyline plantings in order to engender the ambience of an Egyptian oasis. 
Nepean Dam

The last of the Upper Nepean supply dams to be built, Nepean Dam was completed in 1935, signalling the conclusion of the Upper Nepean Scheme. During the period, major advances in engineering technology had been made and the dam represents the culmination of innovation in civil infrastructure, epitomising the first thirty years of the 20th century. The Dam presently serves suburbs of greater Sydney, and remains a symbol of engineering innovation at the turn of the century.

The dam wall is curved in plan and the body built of cyclopean masonry. This consists of large blocks of sandstone quarried at the site, embedded in and surrounded by sandstone concrete. To ensure water tightness, all construction joints are grouted. The upstream face consists of blue metal concrete 1.3m thick while the downstream face is of similar material 0.9m thick. Inspection galleries are set within the wall, with pressure and drainage pipes from the foundations and rubble drains lead into them. Provision is made for any leakage of water past the copper seals in the contraction joints to be conducted into the galleries and thence drained away.

Water is discharged by means of two 0.9m diameter outlet pipes controlled by 0.9m Glenfield-Kennedy needle valves. Although the capacity is similar to the Cataract and Cordeaux Dams, its catchment basin is two to three times greater than those two respectively.

The public area has been maintained by the Water Board and its successors, with picnic grounds, landscaped gardens and a children s playground. Remnants of the interwar period landscape at the Nepean Dam site are mainly concentrated in two areas  around a small park, with cement faux rockwork bedding edges, to the east of the dam wall, including a long line of Roman Cypress (Cupressus sempervirens) along the spillway alignment; and in a park-like picnic area along a terrace above the dam. Features of the latter area include pleasant plantings of mixed deciduous and evergreen exotic trees and Australian trees enclosing a long raised shelf, which is the remnant railway platform from the temporary construction railway, with a series of small timber picnic shelters with a somewhat log cabin-style character.
Building the Upper Nepean Scheme

The Upper Nepean Scheme was commenced in 1880 after it was realised that the Botany Scheme was insufficient to meet Sydney s water supply needs. The Nepean project consisted of the construction of a weir across the Nepean River to divert of the rivers, Cataract, Cordeaux, Avon and Nepean, to the Prospect Reservoir. The Upper Nepean Scheme, completed 1888, was Sydney s fourth water supply. The scheme tapped the headwaters of the Nepean River and its tributaries, the Cataract, Cordeaux, and Avon Rivers. The system consisted of a number of diversion weirs which traversed streams and fed into a collection of tunnels, canals and aqueducts known as the Upper Canal. The canal transported the water to Prospect reservoir. From here, the Lower Canal, which moved the water to a basin at Guildford, now known as Pipehead. At this point, the water was piped to a service reservoir at Pott s Hill, thence to Crown Street and a group of minor service reservoirs located around the City.

By 1902, the population of Sydney had grown to 523,000 and a severe drought caused the water level in Prospect Reservoir to drop below the limit of gravitational flow to the canal. The seriousness of the situation moved the Government in March 1902 to appoint a Royal Commission to inquire into and report upon the Sydney water supply system. The major finding was that a storage dam be constructed to a point just below the junction of Cataract Creek with Cataract River.

The Act authorising the construction of the Cataract Dam am was passed in 1902, providing for a wall 48.7m high. The dam was built by the Public Works Department and the construction contract was let to Lane and Peters. The Principal Assistant Engineer, EM DeBurgh, was given special responsibility for construction. By June 1903, much of the area to be submerged had been cleared of timber and by the end of the year the foundation excavations were in progress.

Construction of the Cataract Dam was completed in 1907. The site for a second storage dam, to be built on the Cordeaux River, was selected by the Water Board in the latter part of 1911 and a gauging weir was constructed. The dam was not begun until 1918 and was completed in 1926. In November of 1918 a Special Board of Experts recommended the construction of the Avon and Nepean Dams as well. The Cordeaux Dam was built by the Public Works Departments.

The Pumping Station at the Prospect Reservoir is a central controlling structure in the Upper Nepean Scheme, regulating the release of water from Prospect Reservoir (maximum rate 450 mega litres/day) to the Lower Canal for conveyance to Pipe Head, thence to Sydney. Since 1960, Prospect has been supplied by Warragamba, rather than the Upper Nepean Dams.

Warragamba Dam

Located about 65 kilometres west of Sydney, about 30 minutes drive from Penrith in western Sydney, Warragamba is a small township of around 500 houses. Originally built as a temporary construction town for the building of the Warragamba Dam starting in 1948, the town was to be demolished at the completion of the Dam in 1960, but many of the towns people wished to purchase their homes and remain. Warragamba has around 20 businesses still trading in the main street, including a cafe, gift shop, variety store, service station and butchers. Warragamba has very much a company town  feel, with its rows of similar looking fibro houses and a flamboyant street layout dominated by curves and circles that looks more like it came from the pen of an artist than a town planner.

While dam visitors still come through the town, Warragamba s tourist heyday was in the decades from the 1960s to the 1980s. The dam was a vast, new piece of civil engineering and the source of much pride. Visitors to the dam could cross the suspension bridge and walk through the tunnels inside the dam wall. They could buy postcard folders of views of the dam and the town, souvenir rulers, giant pencils and souvenir spoons. From 1968 visitors to Warragamba could also visit the African Lion Safari. Lions and tigers roamed free as people drove their cars through the park to observe them.

Warragamba Worker s & Sporting Club has a relaxed and friendly atmosphere where you can catch up or take in the history of Warragamba in its modern surroundings, catering for families is just a small part of what the club provides to the community. Nearby Wallacia houses Panthers 18 Hole Golf Course & Clubhouse as well as Wallacia Bowling Club and the Beautiful Historic Wallacia Hotel.

The dam was built after World War II as a major source of water for the city of Sydney, a role it still plays today. This engineering masterpiece nestles quietly in native bushland a short drive from the town. The dam wall was closed in 1998 during an upgrade and never reopened until January 2013. Today visitors can again delve into the history of the dam builders who laboured to create one of the world s largest domestic water supply dams, and look into the future at the interactive Water for Life  exhibition. There are three viewing platforms at the Warragamba Dam Visitor Centre which offer excellent vistas of the upstream dam wall and Lake Burragorang, as well as a large picnic area. A few minutes  drive from the dam through the Warragamba township, the Eighteenth Street Lookout provides a view of the auxiliary spillway and a distant view of Warragamba Dam wall. Open daily from 10am to 5pm.

A suspension bridge, a remnant from the dam s construction, once crossed over the valley in front of the dam, and those visitors who didn t suffer from vertigo would walk across it and take photographs in front of the dam wall. The bridge was closed in 1987 because of termite damage and then burnt down in the bushfire of 2001.

The two huge pipelines  one 2.1 metres in diameter, the other 3m  that carry water between Warragamba Dam at the foot of the Blue Mountains and Prospect Reservoir in the western suburbs of Sydney are two of the city s most crucial pieces of infrastructure. They are 27 kilometres long and can transport 2600 megalitres a day, providing water to most of Sydney s population. But, just like Warragamba Dam, which was completed in 1960, the pipes are no longer young. Construction work on the smaller pipeline began in 1946, while the large pipeline was completed in 1969. Each year  always in winter when the city s water demand is lower  maintenance work is done on a section of pipeline. When the two pipes are out of action for several weeks, Sydney instead gets its water from what was stored deep in Prospect Reservoir and from increased flows from the 64km of tunnels, canals and aqueducts that are known collectively as the Upper Canal. This connects dams on the Cataract, Cordeaux, Avon and Nepean rivers with Prospect Reservoir.

The name Warragamba comes from the aboriginal words Warra and Gamba meaning water running over rocks. In 1804, George William Evans discovered the Warragamba River, penetrating upstream to the present site of Warragamba Dam. Originally constructed as a workers  settlement during the construction of Warragamba Dam, Sydney s primary water source, in the 1940s the modern town of Warragamba remains on the same site adjacent the dam. The town was built from scratch, including homes, shops, schools and other facilities. On completion of the dam being built many workers bought their homes from the Water Board and stayed on in the township. Warragamba Public School celebrated its fiftieth anniversary in September 1998 despite the fact it was to be demolished after the completion of Warragamba Dam in the 1960s. Warragamba is unusual for an Australian town, as the streets do not have typical names, but are numbered (such as First Street and Eighteenth Street). Ongoing dam works (including safety improvements in the first decade of the 21st century) have severely reduced weekend visitors, though it has picnic and viewing facilities today. The town lost 30 homes and businesses in the Warragamba Bushfire of 2001. Warragamba was home to African Lion Safari until 1991.

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Nepean Dam under construction, 1928

Above: Cordeaux Dam. Below: Avon Dam Walk

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