Nepean Dam facts for kids
Quick facts for kids Nepean Dam |
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The curved arch dam wall
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 Location of Nepean Dam in New South Wales
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| Location | Avon Dam Road, Bargo, New South Wales |
| Coordinates | 34°20′07″S 150°37′01″E / 34.3353731497°S 150.6169604400°E |
| Purpose | Potable water supply |
| Status | Operational |
| Construction began | 1926 |
| Opening date | 1935 |
| Construction cost | A£2,062,000 |
| Operator(s) | Sydney Catchment Authority |
| Dam and spillways | |
| Type of dam | Arch dam |
| Impounds | Nepean River |
| Height (foundation) | 82 metres (269 ft) |
| Length | 216 metres (709 ft) |
| Elevation at crest | 325 metres (1,066 ft) AHD |
| Width (crest) | 6.1 metres (20 ft) |
| Width (base) | 68.6 metres (225 ft) |
| Reservoir | |
| Creates | Nepean Reservoir |
| Total capacity | 81,400 ML (17,900×106 imp gal; 2.15×1010 US gal) |
| Catchment area | 319 square kilometres (123 sq mi) |
| Surface area | 356.5 hectares (881 acres) |
| Official name | Nepean Dam |
| Type | Built |
| Criteria | a., b., c., d., e., f., g. |
| Designated | 18 November 1999 |
| Part of | Utilities - Water group |
| Reference no. | 01368 |
The Nepean Dam is a special dam in New South Wales, Australia. It's located near Bargo and Avon. This dam helps create the Nepean Reservoir, which spreads across these areas. It's one of four important dams that are part of the Upper Nepean Scheme. The Nepean Dam provides drinking water for many places. These include the Macarthur and Illawarra regions, the Wollondilly Shire, and the big city of Sydney. The dam was finished in 1935 and is looked after by the Sydney Catchment Authority. It's also listed on the New South Wales State Heritage Register because of its historical importance.
Contents
Building Sydney's Water Supply
The story of the Nepean Dam began a long time ago. In 1880, people realised that Sydney needed more water. The old water supply system wasn't big enough anymore. So, a new plan called the Upper Nepean Scheme was started. This plan involved building weirs and dams to collect water from several rivers. These rivers included the Cataract, Cordeaux, Avon, and Nepean. The water would then flow to the Prospect Reservoir.
More Dams for a Growing City
By 1902, Sydney still needed more water. Experts suggested building a large dam on the Cataract River. The Cataract Dam was finished in 1907. Later, in 1918, a group of experts recommended building even more dams. This led to the construction of the Cordeaux, Avon, and Nepean Dams. The Cordeaux Dam was completed in 1926. The Avon Dam was finished in 1927. As these dams were almost done, work on the Nepean Dam began in 1925.
Choosing the Nepean Dam Site
The chosen spot for the Nepean Dam was on the Nepean River. It was about 7 miles (11 km) upstream from where the Cordeaux River joins the main river. The dam was designed by engineers from the Public Works Department. Ernest Macartney de Burgh was the chief engineer in charge of the design.
Building the Dam Wall
The Public Works Department started building the dam. In 1928, the project was handed over to the Board of Water Supply and Sewerage. By then, the ground for the dam's base was ready. Much of the equipment from the Avon Dam was moved to the Nepean Dam site. This included large cableways and timber towers. A suspension bridge was also built across the Nepean River. This bridge was later used for the Warragamba Dam project.
Transporting Materials
Building a dam needs a lot of materials. A special railway line was built to bring supplies to the dam site. This line was about 4 km (2.5 miles) long. It connected to the main railway line between Bargo and Yerrinbool. Smaller, narrow-gauge railways were also used at the construction site.
A Town for Workers
A small town was built for the workers and their families. It had cottages for married men and barracks for single men. The town also had metalled roads, a public school, and recreation halls. Medical staff and facilities were available too. This made sure the workers had a good place to live while building the dam.
Changes During Construction
During construction, engineers decided to make the dam wall taller. They added 25 feet (7.6 meters) to its height. This increased the dam's water storage capacity by almost 50%. Work on the dam stopped for a while in 1930. This was due to the Great Depression, which caused money problems. But work started again in 1933 and continued until the dam was finished in 1935.
Spillway Improvements
Even after the dam was ready, there wasn't much rain for three years. But by 1938, the dam was overflowing. Engineers noticed that the overflowing water was causing damage at the base of the dam. So, they built a long concrete channel. This channel, about 2,000 feet (609.7 meters) long, helped direct the floodwaters safely away. This work was completed in 1947.
Connecting the Dams
In the late 1960s, a tunnel was built between the Nepean Dam and the Avon Dam. This tunnel allows water to be moved between the two dams. It helps make sure that Sydney, Wollongong, and Sutherland always have enough water. In the 1980s, the Nepean Dam wall was strengthened. This was done to make sure it met modern safety standards.
How Nepean Dam Works
The Nepean Dam is a large dam built using a method called cyclopean masonry. This means it's made of huge blocks of sandstone rock. These blocks are set into and surrounded by strong concrete. This design makes the dam very strong and watertight.
Dam Features
The dam has special features to help with maintenance. There are inspection tunnels inside the wall. These tunnels allow staff to check for any leaks. There's also an electric lift inside the wall to help maintenance workers move around. Water is released through two large outlet pipes. These pipes are controlled by special valves.
The Nepean Reservoir
The Nepean Reservoir is the lake created by the dam. It has a large catchment area, which means it collects water from a big region. This helps the reservoir fill up quickly. The Nepean Reservoir is an important part of Sydney's water supply system.
Key Facts About Nepean Dam
Here are some interesting facts about the Nepean Dam:
- Total water capacity: 81,400 million litres (17,898 million gallons).
- Construction years: 1926 to 1935.
- Original cost: £2,062,000 (about $4,124,000 AUD).
- Height of dam crest above sea level: 325 meters (1,066 feet).
- Length of the dam wall at the top: 216.4 meters (710 feet).
- Width at the top: 6.1 meters (20 feet).
- Width at the base: 68.6 meters (225 feet).
- Deepest water in the reservoir: 68.6 meters (225 feet).
- Area of the lake: 356.5 hectares (881 acres).
- Area of the catchment (where water is collected): 319 square kilometers (123 square miles).
Water Distribution
The Nepean Dam continues to supply water to Sydney. Water is released into the river below the dam. It then flows through tunnels and canals to the Prospect Reservoir. The dam is also connected to the Avon Dam. This allows water to be shared between the Sydney and Wollongong areas. Water for Picton and Bargo is treated at the Nepean Water Filtration Plant. This plant makes sure the water is clean and safe to drink.
Dam Buildings and Grounds
The Nepean Dam site has several buildings for staff. These include brick cottages from the 1960s and 1980s. There are also older weatherboard cottages, including the original Resident Engineer's Cottage. Near the dam's picnic area, you can find former workshops. These buildings were used for maintenance in the Upper Nepean Catchment area. The area where the construction village used to be is now overgrown. But you can still see old road borders and signs of buildings.
The public areas at the dam are well-maintained. They include picnic grounds, landscaped gardens, and a children's playground. You can see old plantings and features from the 1920s and 1930s. There's even a remnant of the old railway platform, now used for picnic shelters. Stone walls are used to control access around the site. The main entry road still has parts of old tree avenues.
Why Nepean Dam is Important
The Nepean Dam is a very important part of New South Wales's history and engineering. It was the fourth and final major dam built for the Upper Nepean Water Supply Scheme. At the time, it had the highest wall of all the dams in NSW. It was designed by a leading engineer, E.M. de Burgh.
A Major Engineering Feat
Finishing the Nepean Dam was a big step in providing reliable water for Sydney. Even by international standards, it was a huge engineering project for its time. Today, it still plays a vital role in supplying water to the Sydney region. The dam itself is also a beautiful structure. Its design, with its strong, classic style, fits well with the natural surroundings.
Heritage Listing Reasons
The Nepean Dam was added to the New South Wales State Heritage Register in 1999 for several reasons:
- Historical Importance: It shows how Sydney's water supply system grew over time. It was the last of four major dams built between 1903 and 1936. Its construction during the Great Depression also highlights a major public works project during a tough economic period.
- Association with Important People: Engineers like E.M. de Burgh and Gerald Haskins were key to its design and construction. Their knowledge helped create this important dam.
- Beauty and Technical Skill: The dam wall is considered very beautiful. Its curved shape fits well within the river valley. The buildings on the dam, like the crest house, have a special architectural style. The surrounding landscape, with its steep valleys and the large reservoir, creates a picturesque view.
- Community Value: Groups like the National Trust of Australia (NSW) and the Heritage Council of NSW recognise the dam and its grounds as important. They see its value for history, science, culture, and beauty for everyone in NSW.
- Research Potential: The dam's construction methods, like its cyclopean masonry, offer insights into engineering of that era. The old construction areas, including roads and building sites, can still teach us about the lives of the workers who built the dam.
- Uniqueness: The Nepean Dam wall is the highest of all the dams in the Upper Nepean Catchment Area. It was one of the first dams in NSW to use an electric lift inside its wall. The special standard-gauge railway built for its construction was also unique for a dam project in NSW. The planning for the workers' village was very advanced for its time.
- Typical Characteristics: The Nepean Dam shows typical features of dams built in NSW during the early 20th century. This includes its construction style, the use of cableways, and the temporary camps for workers. The way the construction site was later turned into picnic areas also shows common practices. The ongoing maintenance and public access also represent how dams are used in NSW.
