Lake Manapouri
Template:Short description Template:Use New Zealand English Template:Use dmy dates Template:Infobox body of water
Lake Manapouri (Template:Langx)<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> is located in the South Island of New Zealand.<ref name="Peat">Template:Cite book</ref> The lake is situated within the Fiordland National Park and the wider region of Te Wahipounamu South West New Zealand World Heritage Area.<ref name=Johnson1>Template:Cite journal</ref>
Māori HistoryEdit
According to Māori legend Lake Manapouri was created by the tears of two sisters, Moturua and Koronae, who were daughters of an old chief in the region.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Koronae journeyed deep into the forest one day only to become stranded after a fall.<ref name= Peat/> Her sister Moturua went looking for her and when she found Koronae she realised that Koronae could not be rescued.<ref name=Peat/> Moturua lay with Koronae and there they lay until they died, their tears creating Lake Manapouri.<ref name=Peat/> Lake Manapouri means anxious or sorrowful heart because of the grief of the two sisters. However, the present name was given by mistake.<ref name=Peat/> An early settler accidentally called it by the name of one of the Mavora Lakes, which lie between Lake Te Anau and Lake Wakatipu.<ref name="Peat"/> The original name of the lake is believed to have been Roto-ua which translates to Rainy Lake and later Moturau which means Many Islands.<ref name=Peat/> Māori have a long history in the area, finding the lake and its surroundings offering an abundance of food in the form of eels and birds such as pigeon and Kākā (forest parrot).<ref name=Peat/> Manapouri was discovered by Europeans in 1852, by the explorers Charles J Nairn and W H Stevens.<ref name=Peat/>
GeographyEdit
Lake Manapouri was formed by glaciers during the last Holocene.<ref name=Johnson2>Template:Cite journal</ref> The lake is New Zealand’s second deepest lake measuring Template:Convert deep.<ref name=Peat/><ref name = Mark>Template:Cite journal</ref> Lake Manapouri is Template:Convert above sea level however due to glaciers, Lake Manapouri has been cut deep into the ground and the bottom of the lake now lies Template:Convert below sea level.<ref name=Peat/> The lake has four arms, North, South, West and Hope with the smaller indentations of Shallow Bay and Calm Bay.<ref name=Peat/> Lake Manapouri contains 33 islands in total<ref name=Quinn>Template:Cite journal</ref> with 22 of these being wooded.<ref name=Peat/> Lying close to the centre of the lake is the largest island of Pomona Island. Other large islands include Holmwood Island, Rona Island and Mahara Island.<ref name=Peat/> The small settlement of Manapouri lies on the eastern shore.
The Waiau River (Southland) is both a natural inlet and outlet for the lake, flowing into the northeast of the lake from Lake Te Anau, Template:Convert to the north and flowing out from Manapouri's south-eastern end.<ref name=Peat/><ref name=Turner>Template:Cite journal</ref> The outlet however has been diverted due to the development of Manapōuri Hydroelectric Power Station.<ref name=Peat/> Water now flows unnaturally westward to the sea at Deep Cove.<ref name=Peat/> Rainfall in the area is high, however due to the mountains in the west rainfall is much higher in this area.<ref name=Peat/> The average rainfall for the western arm of Lake Manapouri is Template:Convert annually,<ref name=Peat/><ref name=Turner/> while Manapouri Township on the eastern arm of the lake receives less than a third at Template:Convert annually.<ref name=Peat/> Lake Manapouri drains a large catchment area of Template:Convert.<ref name=Turner/> This includes the slopes of the Kepler Mountains, Turret Range and Hunter Mountains which surround all but the eastern shore of the lake.<ref name=Turner/> Water levels in the lake are predominantly high during spring due to snow melt and low in winter.<ref name=Wells>Template:Cite journal</ref>
Lake Manapouri is often described as New Zealand’s most beautiful lake.<ref name=Peat/><ref name=Turner/>
BiodiversityEdit
The area is well renowned for its fishing and high water quality.<ref name=Turner/> Both Lake Manapouri and Lake Te Anau lie within the ultra-oligotrophic index on the trophic state index with clear highly oxygenated waters of very low biological productivity.<ref name=Turner/> Both lakes along with the connecting Waiau River contain the New Zealand longfin eel and introduced brown trout and rainbow trout as well as some Atlantic salmon.<ref name=Turner/> The area is however free from macrophyte Lagarosiphon major an exotic and invasive species which has infiltrated many other New Zealand lakes.<ref name=Turner/>
Lake Manapouri provides 73% of New Zealand’s longfin eel lake habitat protected from commercial fishing.<ref name="Boubée">Template:Cite journal</ref> However the lake has experienced a decline in numbers of longfin eels due to the construction of the hydro- electric dam blocking eel migration.<ref name="Boubée"/> The outflow passage is blocked by the hydro-electric dam which means that eels can be killed when passing through the turbines.<ref name="Boubée"/> A vertical slot fish pass was installed in 1999 and trap and transfer of elvers (young eels) was started in summer 1998/1999.<ref name="Boubée"/> Since the trap and transfer operation commenced in 1998/99 more than 407,000 elvers have been transferred upstream of the Maraoa Control structure.<ref name="Boubée"/> Catch totals in the trap and transfer system can vary in correspondence to surface water temperatures falling below Template:Convert.<ref name="Boubée"/> The trap and transfer technique was successful in improving fish distribution however operations had to be stopped in 2004 due to the concerns that transferring elvers to upstream habitats would spread the exotic invasive algae Didymosphenia geminata.<ref name="Boubée"/> The operation now transfers elvers just past the dam due to these concerns.<ref name="Boubée"/> There is concerns also that the trap and transfer operation does not trap enough silvers eels (eels of breeding age) with an average of 200-400 annually.<ref name="Boubée"/> This however equates to only one silver eel per hectare within the lake which is much lower than standards recommended overseas.<ref name="Boubée"/> More research is needed to understand if trap and transfer is the best option in Lake Manapouri.<ref name="Boubée"/>
Submerged vegetation within Lake Manapouri is mostly native species.<ref name=Wells/> Lake Manapouri has a high diversity of submerged vegetation.<ref name=Wells/> The rare Hydatella inconspicua an endemic shallow water plant was found in many of the Fiordland lakes including Lake Manapouri in 1998, this was the first reporting of it being in the South Island.<ref name=Wells/> The finding meant that the plant was no longer considered endangered.<ref name=Wells/>
SurroundingsEdit
The shoreline in the North and West of the lake remains substantially unaltered since deglaciation.<ref name=Pickrill>Template:Cite journal</ref> Beaches have formed on the lake where rivers bring sediment to areas where the near shore relief is not too steep allowing pocket beaches to form.<ref name=Pickrill/> The beaches around the lake show many similarities to ocean shores.<ref name=Pickrill/> The shape of the lake funnels wind and waves down the long axis which leads to longshore transport or littoral drift of sediment and size selective sorting.<ref name=Pickrill/> There are however a number of differences to ocean shores.<ref name=Pickrill/> The short fetch length produces a narrow range of wave conditions and this low energy limits the size of sediment in transport.<ref name=Pickrill/> Large changes to the beach profile are induced by fluctuations in lake level, major fluctuations can drown beaches.<ref name=Pickrill/> The beaches on the lake develop a distinctive shelf profile whereby beach sediments grade lakeward into fine sand.<ref name=Pickrill/> The outer edge of the shelf is marked by a shelf break and a transition to organic-rich muds on a steep offshore slope.<ref name=Pickrill/> There are a number of different types of beaches including pavement beaches, gravel, mixed sand and gravel beaches and sand beaches.<ref name=Pickrill/>
_towards_Cathedral_Peaks.jpg){kind=link}
The islands around Lake Manapouri are of varying size and isolation.<ref name=Quinn/> Many of the islands contain virtually unmodified vegetation.<ref name=Quinn/> However, there is large diversity between islands in habitat biodiversity, with some islands being completely devoid of plants and soil and other rich in both.<ref name=Quinn/> There is confusion as to some differences with some researchers finding that the area of an island plays a role in species richness<ref name=MacArthur>Template:Cite journal</ref> with others find no correlation at all.<ref name=Quinn/> Red deer have greatly modified much of Fiordlands' vegetation<ref name=Turner/> however only the two largest islands within Lake Manapouri contain introduced red deer while other islands are only occasionally visited by deer.<ref name=Quinn/> The smaller islands around Lake Manapouri are extremely unusual as they contain natural vegetation which has not been harmed by red deer, as the red deer have not been able to reach the islands.<ref name=Turner/> On these islands palatable plants as well as deep moss mat on the forest floor persist under the dense understory layers of the forest.<ref name= Turner/> The Australian brush-tail possum (Trichosurus vulpecula) is not present on the islands.<ref name=Quinn/>
Hydro-power from the lakeEdit
The lake provides hydro-electric power via the Manapōuri Hydroelectric Power Station, in the West Arm, which discharges water through two Template:Convert tailrace tunnels to the sea at Deep Cove in Doubtful Sound.<ref name=Peat/> In 1959 Consolidated Zinc, with the support of the New Zealand government, planned to raise the lake by up to Template:Convert for an increase in power generation for the development of an aluminium smelter.<ref name=Peat/> This resulted in a strong nationwide protest, the Save Manapouri campaign, lasting over a decade, which prevented the raising of the lake from taking place.<ref name=Peat/> The Save Manapouri campaign is regarded as a major milestone in the history of New Zealand's environmental protection.<ref name=Peat/><ref name=StuffGuardians/><ref>Template:Cite magazine</ref> As a result of the campaign, lake levels were required to be maintained at close to natural levels.<ref name=Peat/> The win also saw the establishment in 1973<ref name=StuffGuardians>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> of the Guardians of Lake Manapouri and Te Anau.<ref name=Peat/>
The water pumped through the station is discharged into Doubtful Sound, accounting for 41 percent of the fresh water consumed in New Zealand in 2010.<ref>Dan Hutchinson, "Manapouri NZ's biggest water consumer", 8 December 2010, https://www.stuff.co.nz/southland-times/news/4433869/Manapouri-NZs-biggest-water-consumer</ref> In 2002, the Government — under pressure from the environmental movement — rejected an application of a business, Southland Water 2000, to bottle 40,000 cubic metres of water in 20 hours, twelve times a year, before the water from the power station is released into Doubtful Sound.<ref>NZ Herald, "Fiordland water export scheme rejected", 8 April 2002, https://www.nzherald.co.nz/nz/fiordland-water-export-scheme-rejected/XQINOW24PDBE7BND7LXUXE4OUQ/</ref>
Integrated management of the lakeEdit
The environmental movement of Save Manapouri campaign is considered to be the first environmental movement in New Zealand.<ref name=Turner/> When this movement won the campaign to stop levels on the lake being raised, the government formed the Guardians of Lake Manapouri and Te Anau.<ref name=Turner/> This meant that main campaigners during the Save Manapouri campaign were appointed to advise the managers of the hydro-electric power plant on the management of both Lake Manapouri and Lake Te Anau.<ref name=Turner/> This holistic management between nature conservation and hydro-electric development was unprecedented in New Zealand.<ref name=Turner/>
The group was to “report and make recommendations of Government… on any matter arising from the environmental, ecological and social effects of the construction and operation of the Manapouri-Te Anau electric power scheme on the townships of Manapouri and Te Anau, the lakes and shorelines of Te Anau and Manapouri, and the rivers flowing in and out of these lakes with particular reference to the effects of lake levels on scenic values, conservation, recreation, tourism and other related activities and amenities”.<ref name=Mark/> The guardians were entitled to reports from the Government on actions that had been taken that were deemed relevant so they could fulfil their jobs.<ref name=Turner/>
Defining the natural variation of lake levels was considered very important.<ref name=Turner/> The lake had already experienced slumping due to a lowered lake level.<ref name=Turner/> Also the forest that surrounded the lake was reliant on a variation of water levels.<ref name=Turner/> Shoreline beech forest extended almost 3m below the highest natural lake level.<ref name=Turner/> The roots of this forest could be submerged for a maximum of 50 days meaning that lake levels needed to be maintained within a range that did not exceed this maximum.<ref name=Turner/> The raising of the lake levels too high also had the potential to submerge low-lying islands, many of which contained natural vegetation unharmed by red deer.<ref name=Turner/>
Lake management guidelines were devised from geomorphological and ecological studies correlated with a 37-year lake level record.<ref name=Mark/> The concepts of High, Main and Low Operating Ranges were developed as a basis for management guidelines.<ref name=Mark/> The guidelines were verified in practice and incorporated into legislation in 1981.<ref name=Mark/> In 1987 the groundings for the Resource Management Act 1991 were being laid.<ref name=Mark/> The Government decided that all empowering legislation for hydro-electric stations should be re-issued.<ref name=Mark/> For Lake Manapouri this meant a public process was established whereby a working party was formed to examine and resolve a wide range of environmental issues.<ref name=Mark/> Lake management guidelines and shoreline monitoring were formalised under resource consents.<ref name=Mark/> Also included in the consents was the creation of regulation patterns through the Te Anau and Manapouri control structures to follow more closely to the natural fluctuations of the Waiau River.<ref name=Mark/> The resource consent set up legislation which could restore biological and recreational values to the lower river, particularly the section immediately below the dam.<ref name=Mark/> Compensation was also granted for a range of adverse environmental effects associated with the diverting of water through the power station.<ref name=Mark/>
The Guardians of the Lake were given legal status in the 1990 amendment to the Conservation Act 1987 with additional and similar responsibility for Lake Monowai.<ref name=Turner/> The guardians are still active in 2012 and working alongside Meridian Energy, the current owner of the Lake Manapouri Hydroelectric Power Station.<ref name=energy>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>
See alsoEdit
- List of lakes in New Zealand
- Lakes of New Zealand
- Department of Conservation (New Zealand)
- Save Manapouri campaign
ReferencesEdit
Template:Fiordland Template:WaiauSLD Template:Authority control