Thomson Dam

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Thomson Dam
Thomson Reservoir.jpg
Australia Victoria relief location map.jpg
Red pog.svg
Location of the Thomson Dam in Victoria
Country Australia
Location West Gippsland, Victoria
Coordinates 37°50′34″S146°23′56″E / 37.84278°S 146.39889°E / -37.84278; 146.39889 Coordinates: 37°50′34″S146°23′56″E / 37.84278°S 146.39889°E / -37.84278; 146.39889
Purpose Water supply, irrigation
Status Operational
Construction began 1976
Opening date May 1983 (1983-05)
Owner(s) Melbourne Water
Dam and spillways
Type of dam Embankment dam
Impounds Thomson River
Height (foundation) 166 m (545 ft)
Length 590 m (1,940 ft)
Dam volume 14,170×10^3 m3 (500×10^6 cu ft)
Spillways 1
Spillway type Controlled chute
Spillway capacity 1,040 m3/s (37,000 cu ft/s)
Reservoir
Creates Thomson Reservoir (official); called Lake Thomson
Total capacity 1,123,090 ML (2.4705×1011 imp gal; 2.9669×1011 US gal)
Catchment area 487 km2 (188 sq mi)
Surface area 22.3 km2 (8.6 sq mi)
Normal elevation 494 m (1,621 ft) AHD
Website
Thomson Reservoir at Melbourne Water

The Thomson Dam is a major earth and rockfill embankment dam with a controlled chute spillway across the Thomson River, located about 130 kilometres (81 mi) east of Melbourne in the West Gippsland region of the Australian state of Victoria. The impounded reservoir is officially called Thomson Reservoir, sometimes called Lake Thomson.

Embankment dam large artificial dam

An embankment dam is a large artificial dam. It is typically created by the placement and compaction of a complex semi-plastic mound of various compositions of soil, sand, clay, or rock. It has a semi-pervious waterproof natural covering for its surface and a dense, impervious core. This makes such a dam impervious to surface or seepage erosion. Such a dam is composed of fragmented independent material particles. The friction and interaction of particles binds the particles together into a stable mass rather than by the use of a cementing substance.

Dam A barrier that stops or restricts the flow of surface or underground streams

A dam is a barrier that stops or restricts the flow of water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aquaculture, and navigability. Hydropower is often used in conjunction with dams to generate electricity. A dam can also be used to collect water or for storage of water which can be evenly distributed between locations. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. The earliest known dam is the Jawa Dam in Jordan, dating to 3,000 BC.

Thomson River (Victoria) river in Victoria, Australia

The Thomson River, a perennial river of the West Gippsland catchment, is located in the Gippsland region of the Australian state of Victoria.

Contents

Location and features

The dam is located near the former township of Beardmore and the Baw Baw National Park.

Baw Baw National Park Protected area in Victoria, Australia

The Baw Baw National Park is a national park located on the boundaries between the Central Highlands and Gippsland regions of Victoria, Australia. The 13,530-hectare (33,400-acre) national park is situated approximately 120 kilometres (75 mi) east of Melbourne and 50 kilometres (31 mi) north of the Latrobe Valley. The park contains the Baw-Baw Plateau and borders the Mount Baw Baw Alpine Resort.

Despite opposition from conservationists and farmers, plans for the dam were originally approved in late December 1975 to provide Melbourne with water security. A dam on the Thomson River was preferred because the river had a large flow, high water quality and was elevated high enough to provide water to the upper Yarra system by gravity flow. [1]

Water security

Water security has been defined as "the reliable availability of an acceptable quantity and quality of water for health, livelihoods and production, coupled with an acceptable level of water-related risks". It is realised to the degree that water scarcity is non-existent, or has been decreased or eliminated, and to the degree that floods and contamination of freshwater supplies are non-threatening.

"Sustainable development will not be achieved without a water secure world. A water secure world integrates a concern for the intrinsic value of water with a concern for its use for human survival and well-being. A water secure world harnesses water's productive power and minimises its destructive force. Water security also means addressing environmental protection and the negative effects of poor management. It is also concerned with ending fragmented responsibility for water and integrating water resources management across all sectors—finance, planning, agriculture, energy, tourism, industry, education and health. A water secure world reduces poverty, advances education, and increases living standards. It is a world where there is an improved quality of life for all, especially for the most vulnerable—usually women and children—who benefit most from good water governance."

Early work in the early 1970s saw construction of a 19 kilometres (12 mi) long tunnel through the Thomson Yarra divide to allow water from the Thomson River to flow into the Upper Yarra Reservoir. Work on the dam itself commenced in 1976 and the dam wall was ready to contain water by 1983.

The tunnel, which is located at the northern end of the reservoir, allows water to be transferred west to Upper Yarra Reservoir and then on to Silvan Reservoir for distribution as drinking water in Melbourne.

Silvan Reservoir lake in Australia

The Silvan Reservoir is located in Silvan about 40 kilometres (25 mi) East of Melbourne, Victoria.

Hydroelectricity Generation

Downstream releases from Thomson Reservoir pass through a 7.4 MW [2] hydro power plant, at the base of the dam which generates electricity and feeds it into the state power grid.

Water supply levels

Between 1997 and 2011, drought depleted much of the reservoir's water. In early January 2006, the Thomson Dam was at 45.4%. While there were minor rises in water levels occasionally, the Thomson Dam reached its all-time low of 16.2% on 3 July 2009. [3]

Heavy rainfall in 2010 and 2011 has increased Melbourne's water storages to levels not seen for ten years. [4] The Thomson Dam entered winter 2011 at 39% full [5] and by the end of 2011 had reached 54.4% full. [6]

The last time the reservoir was full and spilling was in the spring of 1996.

The Thomson Dam is managed by Melbourne Water. [7]

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References

  1. Pigram, John J. (2007). Australia's Water Resources: From use to management. Collingwood, Victoria: CSIRO Publishing. p. 94. ISBN   978-0-643-09442-0.
  2. http://www.ghd.com/global/projects/dam-powerful/
  3. Melbourne Water: Water Storage Levels Archive
  4. http://www.melbournewater.com.au/content/water_storages/water_report/weekly_water_report_archives.asp?year=2001&file=wrr010104.html
  5. http://www.melbournewater.com.au/content/water_storages/water_report/weekly_water_report_archives.asp?year=2011&file=wrr110603.html
  6. http://www.melbournewater.com.au/content/water_storages/water_report/weekly_water_report_archives.asp?year=2011&file=wrr111216.html
  7. Melbourne Water