Trevallyn Dam

{{short description|Dam and hydroelectric power station in Tasmania}} {{Use Australian English|date=May 2024}} {{Use dmy dates|date=November 2019}} {{Infobox dam | name = Trevallyn Dam | name_official = | image = Trevallyn Dam.jpg | image_size = 240 | image_caption = Trevallyn Dam in 2009 | image_alt = | location_map = Tasmania | location_map_size = 240 | location_map_caption = Location of the dam in [[Tasmania]] | location_map_alt = | mapframe = yes | coordinates = {{coord|41|26|52|S|147|5|11|E|region:AU-TAS_type:landmark|display=it}} | country = Australia | location = {{TAScity|Launceston}}, Northern [[Midlands (Tasmania)|Midlands]], [[Tasmania]] | purpose = P | status = O | construction_began = | opening = {{start date|1955}} | demolished = | cost = | builder = | designed_by = | owner = | operator = [[Hydro Tasmania]] | dam_type = G | dam_crosses = [[South Esk River]] | dam_height = {{cvt|33|m}} | dam_height_foundation = | dam_height_thalweg = | dam_length = {{cvt|177|m}} | dam_elevation_crest = | dam_width_crest = | dam_width_base = | dam_volume = {{cvt|61|e3m3}} | spillway_count = 1 | spillway_type = [[Spillway#Types|Uncontrolled]] | spillway_length = | spillway_capacity = {{cvt|8500|m3/s}} | spillway_volumetric_flow_rate = | spillway_type2 = | spillway_length2 = | spillway_capacity2 = | spillway_volumetric_flow_rate2 = | spillway_type3 = | spillway_length3 = | spillway_capacity3 = | spillway_volumetric_flow_rate3 = | res_name = Lake Trevallyn | res_capacity_total = {{cvt|12330|ML|acre.ft}} | res_capacity_active = | res_capacity_inactive = | res_catchment = {{cvt|8986|km2}} | res_surface = {{cvt|148|ha}} | res_max_length = | res_max_width = {{cvt|390|m}} | res_max_depth = | res_elevation = {{cvt|124|m}} {{AHD}} | res_tidal_range = | lower_dam_type = | lower_dam_crosses = | lower_dam_height_foundation = | lower_dam_height_thalweg = | lower_dam_length = | lower_dam_elevation_crest = | lower_dam_width_crest = | lower_dam_width_base = | lower_dam_volume = | lower_spillway_count = | lower_spillway_type = | lower_spillway_length = | lower_spillway_capacity = | lower_spillway_volumetric_flow_rate = | lower_spillway_type2 = | lower_spillway_length2 = | lower_spillway_capacity2 = | lower_spillway_volumetric_flow_rate2 = | lower_spillway_type3 = | lower_spillway_length3 = | lower_spillway_capacity3 = | lower_spillway_volumetric_flow_rate3 = | lower_res_name = | lower_res_capacity_total = | lower_res_capacity_active = | lower_res_capacity_inactive = | lower_res_catchment = | lower_res_surface = | lower_res_max_length = | lower_res_max_width = | lower_res_max_depth = | lower_res_elevation = | lower_res_tidal_range = | plant_name = Trevallyn Power Station | plant_coordinates = {{coord|41|25|12|S|147|06|36|E|type:landmark_region:AU-TAS|display=inline}} | plant_operator = Hydro Tasmania | plant_commission = {{start date|1955}} | plant_decommission = | plant_type = R | plant_hydraulic_head = {{cvt|130|m}} | plant_turbines = {{ubl|2 x {{convert|20.9|MW|adj=on|abbr=on}}|2 x {{convert|27|MW|adj=on|abbr=on}}|{{small|(all [[English Electric]] [[Francis turbine|Francis-type]])}}}} | plant_pumpgenerators = | plant_pumps = | plant_capacity = {{cvt|95.8|MW}} | plant_capacity_factor = 0.8 | plant_efficiency = | plant_storage_hours = | plant_annual_gen = {{cvt|492|GWh}} | plant_annual_gen_year = | website = {{URL|hydro.com.au/energy/our-power-stations/great-lake-south-esk-0/trevallyn|hydro.com.au}} | extra = <ref name=ancold>{{cite web |url=http://www.ancold.org.au/wp-content/uploads/2012/10/Dams-Australia-2010-v1-for-website.xls |format=[[MS Excel|Excel]] (requires download) |title=Register of Large Dams in Australia |work=[[Australian National Committee on Large Dams]] |year=2010 |access-date=23 June 2015 |archive-date=12 December 2013 |archive-url=https://web.archive.org/web/20131212120804/http://www.ancold.org.au/wp-content/uploads/2012/10/Dams-Australia-2010-v1-for-website.xls |url-status=dead}}</ref><ref name=report>{{cite web |url=http://www.cathedralrocks.com.au/documents/Our%20Environment/SEGL%20Environmental%20Review.pdf |title=Environmental review document for the South Esk-Great Lake Hydro Catchment |work=Hydro Tasmania |pages=16–17 |url-status=dead |archive-url=https://web.archive.org/web/20110911220858/http://www.cathedralrocks.com.au/documents/Our%20Environment/SEGL%20Environmental%20Review.pdf |archive-date=2011-09-11}}</ref> }} The '''Trevallyn Dam''' is a [[gravity dam]] across the [[South Esk River]] in [[Launceston, Tasmania|Launceston]], [[Tasmania]], Australia. Completed in 1955, the resultant [[reservoir]], Lake Trevallyn, was established for the purpose of generating [[hydroelectricity]] within the northern [[Midlands (Tasmania)|Midlands]] and [[West Tamar]] region. The '''Trevallyn Power Station''' is a [[Run-of-the-river hydroelectricity|run-of-the-river]] [[hydroelectric]] [[power station]], owned and operated by [[Hydro Tasmania]].

== Dam and reservoir overview == The Trevallyn Dam is a concrete gravity dam built on [[dolerite]] bedrock. The dam wall is {{convert|33|m}} high and is {{convert|177|m}} long. When full, Lake Trevallyn has a storage capacity of {{convert|12330|ML|acre.ft|lk=on}} and covers a surface area of {{convert|148|ha}}, drawn from a [[drainage basin|catchment area]] of {{convert|8986|km2}}. The [[spillway]] is {{convert|26.8|m}} high.<ref name=report /> The reservoir also receives water from [[Great Lake (Tasmania)|Great Lake]] via the [[Poatina Power Station]].<ref name=ancold/><ref>{{cite book |title=Dam Technology in Australia 1850-1999 |editor=Cole, B. |publisher=[[ANCOLD]] }}</ref>

=== Reservoir === Lake Trevallyn is the long, narrow lake created by the dam and extends as far as [[Hadspen, Tasmania|Hadspen]] where the first rapids begin at the junction of the [[Meander River (Tasmania)|Meander]] and South Esk rivers. The widest point on the lake is at Stephenson's Bay where it reaches {{convert|390|m}} wide.

Launceston's outer suburb of [[Blackstone Heights, Tasmania|Blackstone Heights]] and part of the Trevallyn State Recreation Area form part of the shore of Lake Trevallyn. Land around the lake is a mixture of suburbs, agricultural land and dry [[eucalypt]] forest.

==== Facilities ==== The lake and some of the surrounding land is used as a recreation area. Most facilities are located at Aquatic Point which include a boat launching ramp, jetty and ski-jump.<ref>{{cite web |url=http://www.mast.tas.gov.au/domino/mast/facweb.nsf/v-web-facilities-area/40AD42C7392F48EECA256B2800318277?OpenDocument&Menu=Marine%20Facilities |title=Facilities - Trevallyn Dam Boat Ramp |work=MAST.tas.gov.au |date= |access-date= }}</ref> A walking track connects Aquatic Point to the dam wall and Trevallyn State Recreation Area. The dam wall features a viewing platform, parkland and barbecue facilities. Most areas of the lake are open to boating and fishing with the exception of waters near the dam and penstock intake.

==== Algal blooms ==== Lake Trevallyn is often prone to algal blooms in the warm summer months. The blooms are due to high nutrient levels from sewerage treatment and fertilizers, limited water movement and warm temperatures. The main species is [[Anabaena circinalis]] and though it has the potential to be toxic, no blooms recorded in the lake have proven to be toxic to date. Since 2007, a monitoring program has been in place to keep a check on algal levels and to notify authorities when blooms occur.<ref>{{cite web |url=http://www.nrmnorth.org.au/-projects/lake-trevallyn-algal-bloom |title=Lake Trevallyn Algal Bloom Monitoring Program |work=NRM North |date= |access-date= }}</ref>

==== Jellyfish ==== In 2009, scientists discovered the freshwater jellyfish, [[Craspedacusta sowerbyi]], in the waters of Lake Trevallyn close to Blackstone Heights. Believed to have been brought by migrating birds from [[China]], the jellyfish were accidentally discovered during routine water testing. The jellyfish are non-venomous and translucent with average sizes around {{convert|2|cm}} across. Though introduced, the jellyfish are believed to have a beneficial impact on the area as they consume the larvae of mosquitoes. A few specimens were temporarily displayed at the [[Queen Victoria Museum and Art Gallery|QVMAG]] in [[Launceston, Tasmania|Launceston]] after the discovery was made.<ref>{{cite web |url=http://www.abc.net.au/news/2009-03-18/scientists-discover-jellyfish-in-lake-trevallyn/1623284 |title=Scientists Discover Jellyfish in Lake Trevallyn |work=[[ABC News (Australia)|ABC News]] |location=Australia |date=2009-03-18 |access-date= }}</ref><ref>{{cite web |url=http://www.themercury.com.au/article/2009/03/19/62135_fun-weird-news.html|title=Jellyfish a cure for mozzies Weird News |work=[[The Mercury (Hobart)|The Mercury]] |date=2009-03-19 |access-date= }}</ref>

== Hydroelectric power station == [[File:Trevallyn Power Station (c1970) (14506931613).jpg|thumb|Trevallyn Power Station, {{circa|1970}}]] Part of the Great Lake and South Esk scheme that comprises three hydroelectric power stations, the Trevallyn Power Station is the final station and is located adjacent to the [[Tamar River (Tasmania)|Tamar River]], north of Launceston, making use of daily flows down the South Esk River.

The dam diverts water through a {{convert|3.3|km|mi|adj=mid|-long}} [[Penstock|penstock pipeline]] to the power station.<ref name=report /> Water flows underground for its entirety except for a short, {{convert|100|m|ft|adj=mid|-long}} portion that leaves the ground near Pitt Avenue due to a valley intersecting the tunnel's course. The pipeline splits underground into four smaller pipes immediately before entering the station's turbines. The water enters the penstock tunnel {{convert|130|m}} above sea level and leaves the power station at sea level, entering the Tamar River via the Tailrace Bay on Tie-Tree Bend.

The Trevallyn and Poatina power stations are the only hydroelectric power stations located in the drainage basin of the South Esk River. The tunnel through which the pipeline runs is cut through dolerite and was excavated by a French tunnelling company. The bay that the used water is discharged into was excavated using mostly steam driven equipment and tram ways with the two tailing mounds now forming the Tailrace Park (south side) and the Tailrace Convention Center (north side). The Tailrace Bay has been adapted to serve recreational purposed and also provides a safe anchorage for yachts.<ref name=hydro>{{cite web |url=http://www.hydro.com.au/energy/our-power-stations/great-lake-south-esk |title=Trevallyn Power Station {{!}} Our power stations: Great Lake - South Esk |work=[[Hydro Tasmania]] |date=2015 |access-date=7 July 2015 }}</ref>

The power station was commissioned in 1955 by the [[Hydro Tasmania|Hydro Electric Corporation (TAS)]] and replaced the [[Duck Reach Power Station]]. The station has two {{convert|20.9|MW|adj=on}} [[English Electric]] [[Francis turbine|Francis-type]] [[water turbine|turbines]] and two {{convert|27|MW|adj=on}} English Electric Francis-type turbines, with a combined generating capacity of {{convert|95.8|MW}} of electricity.<ref name=hydro/><ref name=hydrotech/> Within the station building, each turbine has a fully embedded spiral casing. A main inlet valve is located in the station immediately upstream of each turbine for maintenance and security purposes. No. 1 and no. 2 machines are equipped with a turbine relief (bypass) valve to reduce pressure rise in the turbine and penstock during rapid guide vane closure. The station output, estimated to be {{convert|492|GWh||lk=on}} annually,<ref name=ancold/> is fed to [[TasNetworks]]' transmission grid via two three-phase [[Alstom]] generator transformers and two 3-phase English Electric generator transformers to the outdoor switchyard.<ref name=hydrotech>{{cite web |url=http://www.hydro.com.au/system/files/attachments/Trevallyn_Power_Station-Fact-Sheets.pdf |archive-url=https://web.archive.org/web/20120324104540/http://www.hydro.com.au/system/files/attachments/Trevallyn_Power_Station-Fact-Sheets.pdf |url-status=dead |archive-date=24 March 2012 |title=Trevallyn Power Station Fact Sheet: Technical fact sheet {{!}} Energy: Our power stations |work=[[Hydro Tasmania]] |access-date=7 July 2015 }}</ref>

Water is discharged into the Tamar River at sea level by an open tailrace channel.

The construction village, named Marrawaylee, is now part of the suburb of West Riverside and is accessed by Pomona Road. The power station and the open land for the transmission lines now serve as a border between the Launceston suburbs of Riverside and Trevallyn.

==See also== {{stack|{{Portal|Australia|Water|Renewable energy}}}} * [[List of power stations in Tasmania]] * [[List of reservoirs and dams in Australia#Tasmania|List of reservoirs and dams in Tasmania]] * [[List of run-of-the-river hydroelectric power stations]]

==References== <references/>

== External links == {{commons category|Trevallyn Dam}} * {{cite web |work=[[Hydro Tasmania]] |title=Trevallyn Power Development |date= |access-date= |url=http://www.hydro.com.au/home/Energy/Tasmanian+Hydro+Electric+Schemes/Catchment+Areas/Great+Lake+and+South+Esk+Catchment/Trevallyn+Power+Development.htm }}

[[Category:1955 establishments in Australia]] [[Category:Buildings and structures in Launceston, Tasmania]] [[Category:Dams completed in 1955]] [[Category:Energy infrastructure completed in 1955]] [[Category:Gravity dams]] [[Category:Hydroelectric power stations in Tasmania]] [[Category:Hydro Tasmania dams]] [[Category:Run-of-the-river power stations]] [[Category:Tamar River]]