Happy Valley Reservoir

Infobox lake
lake_name = Happy Valley Reservoir
image_lake = Happy_Valley_Reservoir_20070223.jpg
caption_lake = View of Happy Valley Reservoir in early 2007
image_bathymetry =
caption_bathymetry =
location = South Australia
coords = coord|35.073|S|138.572|E|region:AU_type:waterbody|display=inline,title
type = reservoir
inflow =
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catchment =
basin_countries = Australia
length =
width =
area = 1.88 km²
depth =
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Happy Valley Reservoir is one of the oldest reservoirs in South Australia, having been built between 1892 and 1897 at a cost of AU$1.8 million.cite web | accessmonthday =September 24 | accessyear =2005 | url =http://www.sawater.com.au/SAWater/Education/OurWaterSystems/Water+Storage+%28Reservoirs%29.htm | title = Water Storage (Reservoirs): Happy Valley Reservoir | year =2005 | publisher =SA Water ] The reservoir supplies over a half a million people, from Adelaide's southern extent to the city-centre itself.

The original Happy Valley township and cemetery were completely flooded by the new reservoir requiring their relocation. The township was moved to the east while the cemetery, which is still in use today, was moved to the west and relocated alongside the base of the dam wall. The reservoir acts as a 'holding pond' for water directed it to it from the Clarendon Weir via a five km long underground tunnel. The 1.8 m diameter tunnel was bored simultaneously from both ends and when meeting had a deviation of 25 mm. Its deepest point underground is 122 m where it passes through a hill. On 7 August 1896 the tunnel's inlet valve was opened by Sir Fowell Buxton and the reservoir began filling. [ [http://www.slsa.sa.gov.au/manning/adelaide/water/water.htm Adelaide Water Supply.] The Manning index of South Australian history. State Library of South Australia]

Initially 15 kilometres from Adelaide, the reservoir is now largely enveloped by the city's southern suburbs, of which the relocated Happy Valley village is one.cite web | last =Conlon | first =Keith | authorlink =Keith Conlon |accessmonthday =September 24 | accessyear =2005 | url =http://www.postcards.sa.com.au/features/happy_valley.html | title =Open Day at Happy Valley | work=Postcards | publisher =Nine Network ] The Happy Valley Reservoir is relatively small in capacity; holding only 11,500 megalitres, it is dwarfed by Mount Bold Reservoir which is at least four times larger. It is the site of the biggest water treatment plant in Adelaide and is responsible for providing more than 40% of the city's water.cite web | date=2005-03-21 | accessmonthday =September 24 | accessyear =2005 | url =http://www.parks.sa.gov.au/yurrebilla/parkparticipants/water/index.htm | title = SA Water Reserves: Happy Valley| publisher =South Australian Department for Environment and Heritage ]

Water from the dam was originally supplied to Adelaide through a tunnel under Black Road. In the early 1960s, the original intake tunnel from the Clarendon Weir was increased in size to allow access by maintenance vehicles, and a second outlet tunnel was constructed under South Road. In the late 1980s, this new tunnel became the outlet for the water filtration plant, and the original outlet was abandoned.. [ [http://www.parliament.sa.gov.au/NR/rdonlyres/E81F9DE9-3ACB-4815-8EC6-7F5864EABFE1/3088/hansard3july2002.pdf Parliament of south Australia official Hansard Report] Happy Valley Reservoir Rehabilitation Project Wednesday 3 July 2002 pdf]

Between 2002 and 2004, the Reservoir underwent a major renovation as part of AU$22 million rehabilitation project aimed at enhancing the Reservoir to meet guidelines of best practice for dam management at both international and national levels. The reservoir's earth wall was particularly susceptible to piping failure (a small leak, called a pipe, gets larger until the dam collapses) and the renovations lowered the risk of dam wall failure from 1 in 1,200 to an estimated 1 in 100,000. Part of this project included an upgrade of the dam wall designed to also increase flood storage capacity and reduce risk of damage in the event of an earthquake. [cite web | accessmonthday =September 24 | accessyear =2005 | url =http://www.sawater.com.au/NR/rdonlyres/7DF9CFDB-90D2-4864-86CD-6DC8F8C932A6/0/HVBrochure.pdf | format = PDF | title = Happy Valley Reservoir Wall Upgrade | publisher =SA Water ]

With the lowering of the water level during renovations exposing the original Happy Valley township for the first time, archaeologists took the opportunity to excavate the site. Despite the township being entirely intact and undamaged when flooded in 1896, very little was found apart from scattered bricks and the foundations of several buildings.Fact|date=August 2007

*Capacity: 11,500 megalitres
*Length of wall: 1,155 m
*Height of wall: 23.6 m
*Type of wall: Earth with clay core
*Area of water spread: 1.88 km²

ee also

*List of reservoirs and dams in Australia

References