Lake Alexandrina, New Zealand
Encyclopedia
Lake Alexandrina is a lake located in the Mackenzie Basin
of New Zealand
's South Island
. It lies immediately to the west of the much larger Lake Tekapo and further to the east of Lake Pukaki, located to the north of Lake Tekapo township
. It is a shallow lake with distinct indications of glacial origin and is spring fed with an outlet on its eastern shore mid way down the lake. The outlet feeds into a smaller lake, Lake MacGregor before feeding into Lake Tekapo described as “Opaque and milky blue” in colour. In the desert terrain of the Mackenzie Plains, Lake Alexandrina is considered as an “oasis of life”.
Lake Alexandrina is a nature reserve and a delight to a fisherman, well documented for its brown and rainbow trout
and salmon
.
Categorised as a Canterbury High County lake in the Mackenzie Basin
, it lies a short distance from Lake Tekapo while also being connected to it. Lake Alexandrina is approached from the State Highway 8 via the Godley Peaks Road. The lake, located at an altitude of 732 metres (2,401.6 ft), covers an area of 640 hectares (1,581.5 acre) with width of 0.9 kilometre (0.559235462984826 mi) and extending to a length of 7.2 kilometres (4.5 mi). Its shores are flat. The maximum water depth in the lake is reported to be 27 metres (88.6 ft). The lake catchment has landscape that provides for plentiful wildlife but also has extensive cultivation which brings in a lot of nutrients, enriching the lake's with phosphorus
.
The lake's annual balance is contributed by surface streams: 5.72 million m3 (27%), overland flows: 1.11 million m3 (5%), ground water sources: 10.1 million m3 (48%) and precipitation: 4.11 million m3 (20%). The storage in the lake lasts four years.
levels of 0.4–3.8 mg/1 have recorded during observations carried out between November 1978 and March 1979. The total phosphorus
at 1 m depth was 0.009–0.015 mg/L as measured in March 1979. The reasons attributed to high nutrient content and consequent high degree of phosphorus levels are due to nutrients entering from the lake catchment, underground sources, grazing on the periphery of the lake, human habitations around the lake, aerial spray and stocking in the trout-spawning streams.
, shoveler
and scaup
. Australia
n Shoveller is a common bird seen in the lake area, as well as pelicans, black swans
and ducks. Six species of waterbirds have been recorded in total. Paradise Shelduck
flock here during the summer season, seeking sanctuary when they become flightless during their moult. Freshwater snail
s Potamopyrgus antipodarum have also been analysed in the basin area. For example, studies in 1994 found that there are more male snails in the lake's shallow water than females, and that snails are sicker in shallow water than deep water.
Vegetation
The breeding of the Elodea canadensis species has been inhibited at Lake Alexandrina because of the steep slopes on the east and west sides of the lake, as well as turbulence caused by high winds of 10–14 m/s.
Aqua fauna
The lake has plentiful stocks of brown trout, rainbow trout and salmon, which are well known to fishing enthusiasts. The trouts are not found in abundance because of overfishing and inadequate spawning duration. However, the fish do grow to a large size, especially the trout, each weighing as much as 2.5 kilograms (5.5 lb) on an average. Some of prize catch could be of 4.5 kilograms (9.9 lb) weight for rainbows and 6.3 kilograms (13.9 lb) for brown variety trout (which generally are found along the shores of the lake where flies and insects abound).
.
Threats
The threats to the lake waters that were identified in the 1980s were the regular occurrence of algal (Anabaena
) blooms, which were a result of high nutrient levels of phosphorus, survival of wildlife, and recreational fishery. It was assessed by measurements that nearly 50% of the phosphorus was contributed by groundwater, with 32% from surface water inflows and only 3–9% from hut settlements. This resulted in poor quality of the lake waters and subsequently, measures to check the phosphorus content in the lake received priority attention of the Government of New Zealand.
Conservation measures
In order to take adequate remedial measures to check the inflow of nutrients into the lake, which had raised the phosphorus content in the lake waters to unacceptable levels, in 1984, the "Lake Alexandrina Steering Committee" was set up which identified the problem areas causing deterioration of water quality as due to phosphorus as also from the hut settlements at the outlet and south end, and from agricultural sources. The Taranaki Catchment Commission and the Waitaki Catchment Commission, who examined this issue in 1987, also concluded that though the inflows exceeded outflows, but they did not contribute to the storage due the high sediment contribution which vitiated the storage. Consequent to their study of recorded high total phosphorus levels causing the blooms and creating threats to wildlife and the recreational fisheries, the Commission prescribed interim management guidelines such as: Total cessation of aerial top dressing within 500 metres (1,640.4 ft) of the eastern shore and 800 metres (2,624.7 ft) of the western shore and around the flow sources in to the lake; restrictions on fertiliser use for agriculture; access to streams for spawning activities and to establish a "deer fence" on the northern end of the wetland; stop all activities related to cultivation on the shores of the lake; stop building of the hut settlements around the lake; install individual household effluent storage or septic tanks; and diversion of sewage outside the catchment. These measures were implemented by the Mackenzie District Council under a District Plan 1997, under the title "Lake Side Protection Area around Lake Alexandrina". Progressively implemented since 1985, the redeeming feature of these actions is that the heavy algal blooms of the 1980s are now infrequent and limited to a frequency occurrence of once in three years.
Mackenzie Basin
The Mackenzie Basin , is an elliptical intermontane basin, located in the Mackenzie and Waitaki Districts, near the centre of the South Island of New Zealand. It is the largest such basin in New Zealand...
of New Zealand
New Zealand
New Zealand is an island country in the south-western Pacific Ocean comprising two main landmasses and numerous smaller islands. The country is situated some east of Australia across the Tasman Sea, and roughly south of the Pacific island nations of New Caledonia, Fiji, and Tonga...
's South Island
South Island
The South Island is the larger of the two major islands of New Zealand, the other being the more populous North Island. It is bordered to the north by Cook Strait, to the west by the Tasman Sea, to the south and east by the Pacific Ocean...
. It lies immediately to the west of the much larger Lake Tekapo and further to the east of Lake Pukaki, located to the north of Lake Tekapo township
Lake Tekapo (town)
TekapoUrban AreaPopulation:Extent:Territorial AuthorityName:Mackenzie District CouncilPopulation:Mayor:Website:Extent:Regional councilName:Environment Canterbury...
. It is a shallow lake with distinct indications of glacial origin and is spring fed with an outlet on its eastern shore mid way down the lake. The outlet feeds into a smaller lake, Lake MacGregor before feeding into Lake Tekapo described as “Opaque and milky blue” in colour. In the desert terrain of the Mackenzie Plains, Lake Alexandrina is considered as an “oasis of life”.
Lake Alexandrina is a nature reserve and a delight to a fisherman, well documented for its brown and rainbow trout
Trout
Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...
and salmon
Salmon
Salmon is the common name for several species of fish in the family Salmonidae. Several other fish in the same family are called trout; the difference is often said to be that salmon migrate and trout are resident, but this distinction does not strictly hold true...
.
Geography
Mackenzie Basin
The Mackenzie Basin , is an elliptical intermontane basin, located in the Mackenzie and Waitaki Districts, near the centre of the South Island of New Zealand. It is the largest such basin in New Zealand...
, it lies a short distance from Lake Tekapo while also being connected to it. Lake Alexandrina is approached from the State Highway 8 via the Godley Peaks Road. The lake, located at an altitude of 732 metres (2,401.6 ft), covers an area of 640 hectares (1,581.5 acre) with width of 0.9 kilometre (0.559235462984826 mi) and extending to a length of 7.2 kilometres (4.5 mi). Its shores are flat. The maximum water depth in the lake is reported to be 27 metres (88.6 ft). The lake catchment has landscape that provides for plentiful wildlife but also has extensive cultivation which brings in a lot of nutrients, enriching the lake's with phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
.
The lake's annual balance is contributed by surface streams: 5.72 million m3 (27%), overland flows: 1.11 million m3 (5%), ground water sources: 10.1 million m3 (48%) and precipitation: 4.11 million m3 (20%). The storage in the lake lasts four years.
Chemical properties
The lake has been classified as mesotrophic type. ChlorophyllChlorophyll
Chlorophyll is a green pigment found in almost all plants, algae, and cyanobacteria. Its name is derived from the Greek words χλωρος, chloros and φύλλον, phyllon . Chlorophyll is an extremely important biomolecule, critical in photosynthesis, which allows plants to obtain energy from light...
levels of 0.4–3.8 mg/1 have recorded during observations carried out between November 1978 and March 1979. The total phosphorus
Phosphorus
Phosphorus is the chemical element that has the symbol P and atomic number 15. A multivalent nonmetal of the nitrogen group, phosphorus as a mineral is almost always present in its maximally oxidized state, as inorganic phosphate rocks...
at 1 m depth was 0.009–0.015 mg/L as measured in March 1979. The reasons attributed to high nutrient content and consequent high degree of phosphorus levels are due to nutrients entering from the lake catchment, underground sources, grazing on the periphery of the lake, human habitations around the lake, aerial spray and stocking in the trout-spawning streams.
Ecology
The lake catchment is biologically rich, with 45 species of birds, which include the southern crested grebeGrebe
A grebe is a member of the Podicipediformes order, a widely distributed order of freshwater diving birds, some of which visit the sea when migrating and in winter...
, shoveler
Shoveler
The shovelers, formerly known as shovellers, are four species of dabbling ducks with long, broad spatula-shaped beaks:* Red Shoveler, Anas platalea* Cape Shoveler, Anas smithii* Australasian Shoveler, Anas rhynchotis...
and scaup
Scaup
Scaup may refer to:* Scottish Conservative and Unionist Party, a political party in Scotland* One of three species of diving duck:** Greater Scaup or just Scaup, Aythya marila** Lesser Scaup, Aythya affinis...
. Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
n Shoveller is a common bird seen in the lake area, as well as pelicans, black swans
Black Swans
Black Swans is a 2005 Dutch drama film.The film won a Golden Calf for best sound at the Netherlands Film Festival in 2005.-Plot:Marleen works as a volunteer in a rest home in Spain. When she meets Vince they are attracted to each other. Their passionate relationship has its ups and downs, and...
and ducks. Six species of waterbirds have been recorded in total. Paradise Shelduck
Paradise Shelduck
The Paradise Shelduck is a large goose-like duck endemic to New Zealand. They are known to the Māori as Pūtangitangi but now commonly referred to as the "Paradise duck", and are prized game birds...
flock here during the summer season, seeking sanctuary when they become flightless during their moult. Freshwater snail
Freshwater snail
A freshwater snail is one kind of freshwater mollusc, the other kind being freshwater clams and mussels, i.e. freshwater bivalves. Specifically a freshwater snail is a gastropod that lives in a watery non-marine habitat. The majority of freshwater gastropods have a shell, with very few exceptions....
s Potamopyrgus antipodarum have also been analysed in the basin area. For example, studies in 1994 found that there are more male snails in the lake's shallow water than females, and that snails are sicker in shallow water than deep water.
Vegetation
The breeding of the Elodea canadensis species has been inhibited at Lake Alexandrina because of the steep slopes on the east and west sides of the lake, as well as turbulence caused by high winds of 10–14 m/s.
Aqua fauna
The lake has plentiful stocks of brown trout, rainbow trout and salmon, which are well known to fishing enthusiasts. The trouts are not found in abundance because of overfishing and inadequate spawning duration. However, the fish do grow to a large size, especially the trout, each weighing as much as 2.5 kilograms (5.5 lb) on an average. Some of prize catch could be of 4.5 kilograms (9.9 lb) weight for rainbows and 6.3 kilograms (13.9 lb) for brown variety trout (which generally are found along the shores of the lake where flies and insects abound).
Conservation
Lake Alexandrina is one of New Zealand's Scenic Reserves, a valid Crown Protected AreaProtected areas of New Zealand
Protected areas of New Zealand are on both public and private land. Nearly 30 percent of the land mass of New Zealand is in public ownership and has some degree of protection...
.
Threats
The threats to the lake waters that were identified in the 1980s were the regular occurrence of algal (Anabaena
Anabaena
Anabaena is a genus of filamentous cyanobacteria that exists as plankton. It is known for its nitrogen fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyanobacteria that produce neurotoxins, which are harmful to...
) blooms, which were a result of high nutrient levels of phosphorus, survival of wildlife, and recreational fishery. It was assessed by measurements that nearly 50% of the phosphorus was contributed by groundwater, with 32% from surface water inflows and only 3–9% from hut settlements. This resulted in poor quality of the lake waters and subsequently, measures to check the phosphorus content in the lake received priority attention of the Government of New Zealand.
Conservation measures
In order to take adequate remedial measures to check the inflow of nutrients into the lake, which had raised the phosphorus content in the lake waters to unacceptable levels, in 1984, the "Lake Alexandrina Steering Committee" was set up which identified the problem areas causing deterioration of water quality as due to phosphorus as also from the hut settlements at the outlet and south end, and from agricultural sources. The Taranaki Catchment Commission and the Waitaki Catchment Commission, who examined this issue in 1987, also concluded that though the inflows exceeded outflows, but they did not contribute to the storage due the high sediment contribution which vitiated the storage. Consequent to their study of recorded high total phosphorus levels causing the blooms and creating threats to wildlife and the recreational fisheries, the Commission prescribed interim management guidelines such as: Total cessation of aerial top dressing within 500 metres (1,640.4 ft) of the eastern shore and 800 metres (2,624.7 ft) of the western shore and around the flow sources in to the lake; restrictions on fertiliser use for agriculture; access to streams for spawning activities and to establish a "deer fence" on the northern end of the wetland; stop all activities related to cultivation on the shores of the lake; stop building of the hut settlements around the lake; install individual household effluent storage or septic tanks; and diversion of sewage outside the catchment. These measures were implemented by the Mackenzie District Council under a District Plan 1997, under the title "Lake Side Protection Area around Lake Alexandrina". Progressively implemented since 1985, the redeeming feature of these actions is that the heavy algal blooms of the 1980s are now infrequent and limited to a frequency occurrence of once in three years.