Warragamba Dam is a heritage-listed dam in the outer South Western Sydney suburb of Warragamba, Wollondilly Shire in New South Wales, Australia. It is a concrete gravity dam, which creates Lake Burragorang, the primary reservoir for water supply for the city of Sydney. The dam wall is located approximately W of Sydney central business district, 4½ km SW of the town of Wallacia, and 1 km NW of the village of Warragamba.
The dam was devised as part of a collective engineering response to Sydney's critical water shortage during World War II and was originally known as the Warragamba Emergency Scheme. Constructed between 1948 and 1960, the dam created capacity for a reservoir of and is fed by a catchment area of . The surface area of the lake covers of the now-flooded Burragorang Valley. It was designed and built by the Metropolitan Water Sewerage and Drainage Board. A small hydroelectric power station was incorporated into the design of the dam but has been disconnected from the grid since 2001.
The property is owned by WaterNSW, an agency of the Government of New South Wales. The dam was added to the New South Wales State Heritage Register on 18 November 1999.
Drought has severely depleted the level of the dam at times: on 8 February 2007 it recorded an all-time low of 32.5% of capacity. On 2 March 2012, it overflowed for the first time in fourteen years. It overflowed again in 2016, March 2021, and April 2024.
History
One of the first places in the Gundungurra traditional homelands that most appealed to the Anglo-Celtic settlers were the river flats of the Burragorang Valley (now flooded under Lake Burragorang). Even before the valley was officially surveyed in 1827-1828, many early settlers were already squatting on blocks that they planned to officially occupy following the issue of freehold title grants. From the Burragorang Valley and using Aboriginal pathways, other valleys to the west were occupied and developed by the settlers with construction of outstations and stock routes. These cattle entrepreneurs were then followed by cedar-wood extractors and miners. The site was reviewed and approved by Dr John Savage, considered the pre-eminent expert in this field, and formally accepted by the Metropolitan Water, Sewerage and Drainage Board on 2 October 1946.
Dam construction began in 1948 and was completed in 1960. The resulting dam of the Warragamba River formed Lake Burragorang, which is one of the largest reservoirs for urban water supply in the world.
The dam wall comprises of concrete. It was laid as interlocking blocks roughly on each side, which were later grouted together to form a continuous, monolithic wall. It is so large that engineers had to use two techniques to prevent the temperature from becoming too hot as the concrete set. One was to add ice to the wet concrete, the first application of this technique in Australia. The other was to embed cooling pipes into the concrete and circulate chilled water through the pipes. As a result, the dam wall was cooled in a few months instead of the estimated 100 years it would have taken to cool naturally.
The dam created capacity for a reservoir of and is fed by a catchment area of . The surface area of the lake covers of the now flooded Burragorang Valley. The auxiliary spillway is normally closed by a series of fuse plugs that are designed to be washed away in the event of an extreme flood event. transmitting its output over a 132 kV transmission line to a Penrith Substation. Water levels very rarely became high enough to allow operation of the generators. By 2001, it was rarely used and was disconnected from the electricity grid.
21st century re-engineering and enhancements
In 2006, the Warragamba Deep Water Storage Recovery Project, part of the Metropolitan Water Plan, penetrated the base of the dam wall to allow the previously inaccessible lowest water in the reservoir to be available. This new outlet was below the minimum level required for gravity flow, which delivered water from the existing outlets. The project constructed a new pumping station downstream of the dam. The new pumping station is within the Emergency Scheme pumping station chamber. This project provided access to eight per cent more water or approximately six months of extra supply. On 15 April 2006, the project reached a major milestone when it increased the available storage from to .
Other recent major work includes a complete upgrade of the three passenger lifts within the dam wall, an upgrade of the travelling crest crane and a complete upgrade of the four water supply outlets in the valve house, which includes the replacement of the major valves.
Proposed raising of dam wall
Since 2017, WaterNSW has been working on a risk-mitigation project, aimed at protecting human life and property in the floodplain catchment area in case of major flooding, primarily by raising the dam wall by up to . and reducing the need for urgent evacuations.
However, there are concerns for the more than 50 recognised Aboriginal heritage sites in the of World Heritage Area that would be flooded, parts of which were badly burnt in the 2019–2020 bushfires in Australia. The box gum grassy woodlands are home to threatened species of birds, including up to 50% of the remaining population of the critically endangered regent honeyeater, as well as koalas and greater gliders.
In September 2020, the New South Wales Government was ordered by the federal Department of Agriculture, Water and the Environment to re-do their Indigenous heritage work, concerned that NSW has not adequately addressed the concerns of Gundungurra and other traditional owners in their cultural heritage surveys. The federal review also said that the environmental impact assessment lacked detail on how the project could affect species such as the platypus and echidna. Engineering experts have also questioned the modelling done by Infrastructure NSW.
In April 2024, after the seventh flood in 18 months in northwestern Sydney, the NSW water minister Rose Jackson proposed the idea of lowering Warragamba Dam's storage and supplementing it with desalinated water to decrease flood danger in Sydney's north-west. The plan would mean a proportion of the dam's capacity would be brushed aside for flood mitigation. According to her, this will be cheaper than raising the dam's wall by 14 metres (a proposal scrapped by the Labor government in 2023). University of Sydney water expert, Professor Stuart Khan stated that the Sydney Desalination Plant can produce 90 gigalitres of water a year, which would drop 40% of the dam's capacity.
Catchment
The catchment area is . The areas closest to the lake, making up around 30% of the total catchment, are restricted access special areas. Most of the rest
Although the engineers did not design Warragamba Dam as a flood control measure, it can mitigate flooding by holding floodwaters back while the reservoir fills.
Dam level crises and water restrictions
There have been times when drought has seriously depleted the dam. In March 1983, Lake Burragorang's level reached a low of 45.4% of capacity, only to reach the maximum level in the mid-1990s; as a consequence, the gates were opened (there was a significant spill in August 1998) and on 8 February 2007 it recorded an all-time low of 32.5% of capacity.
The New South Wales State Government tried to reduce this risk by implementing water restrictions and commissioned the construction of a desalination plant, at Kurnell. Heavy rains between June 2007 and February 2008 restored the dam level to around 67%. Despite this, Level 3 water restrictions remained in place until 21 June 2009. The dam began spilling at 18:53 (AEDT) on 2 March 2012 and again on 20 April 2012. In March 2022, following heavy rains across NSW and Queensland, the dam once again overflowed, flooding areas downstream.
Statistical overview
{| class="wikitable"
|-
!colspan=2| Key dam structures
|-
|scope="col" width="250px" |Height ||scope="col" width="250px" align="right"|
|-
|Length ||align="right"|
|-
|Thickness at top ||align="right"|
|-
|Thickness at base ||align="right"|
|-
|Width of central spillway ||align="right"|
|-
|Width of auxiliary spillway (at mouth) ||align="right"|
|-
|Length of auxiliary spillway ||align="right"|
|-
|Hydro-electric plant capacity ||align="right"|
|}
{| class="wikitable"
|-
!colspan=2| Key reservoir statistics
|-
|scope="col" width="250px" |Available storage (when full) ||scope="col" width="250px" align="right"|
|-
|Total capacity (when full) ||align="right"|
|-
|Surface area ||align="right"|
|-
|Length of lake ||align="right"|
|-
|Length of foreshores ||align="right"|
|-
|Deepest point ||align="right"|
|-
|Catchment area ||align="right"|
|-
|Average annual rainfall ||align="right"|
|}
Access and recreation
Warragamba Dam was a popular picnic spot for Sydneysiders, but access to the public was restricted after 1999 due to A$240 million of upgrades in that time. It reopened to the public on 8 November 2009.
Access to the dam wall and terrace gardens opened from 23 December 2012 to 28 January 2013 at weekends and public holidays.
Heritage listing
The Emergency Scheme is representative of the collective engineering response to Sydney's critical water shortage during the Second World War period. It was the first stage in the storage and extraction of water from the Warragamba River, and was preliminary to the Waragamba Dam. All of the components are excellent examples of the civil engineering skills of the times; the Balance Reservoir is particularly significant because it provides a stilling pool downstream of Warragamba Dam for the purpose of flood discharge; the group of five cottages associated with the construction of the dam are considered to be of high significance because they housed the operations staff between 1940 and 1959. These have since been incorporated into the Warragamba township, one of the largest townships in the Shire of Wollondilly.
- The place possesses uncommon, rare or endangered aspects of the cultural or natural history of New South Wales.
- This item is assessed as historically rare statewide and as well as scientifically rare statewide.
See also
- 1998 Sydney water crisis
- Warragamba – township originally built to house dam builders.
References
Bibliography
Attribution
External links
- WaterNSW – Warragamba Dam
- FloodSafe NSW Warragamba FAQ