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Lakes

by  Simon Nathan

Mirror-like waters reflecting snow-capped mountains – a classic snapshot of New Zealand’s natural beauty. The hundreds of lakes are jewels in the country’s crown, treasured as fertile wetlands, rare habitats, tranquil fishing spots and swimming holes.


New Zealand lakes

New Zealand is a land of lakes, often painted and photographed. Used widely for fishing and boating, they are also a source of water for drinking, irrigation and electricity generation. Each lake has its own characteristics that are treasured by those who live nearby.

Lake facts and figures

  • Excluding offshore islands, New Zealand has 775 lakes that are at least 0.5 kilometres long. Lakes cover about 1.3% of the land area.
  • The largest is Lake Taupō, in the central North Island, with an area of 623 square kilometres. It lies in a deep basin created by a massive eruption of the Taupō volcano, about 26,500 years ago.
  • The eight next-largest lakes are all glacial lakes in the South Island.
  • The deepest lake is Lake Hauroko, in western Southland, which reaches 462 metres. It is the 16th deepest lake in the world.
  • The Maori word for lake is ‘roto’, and many lake names start with this. Some examples are: Rotoiti (small lake), Rotoroa (long lake), Rotomanu (lake of birds) and Rotomahana (warm lake).

Bathymetry: studying lake depth

The underwater shape and depth (bathymetry) of the larger lakes is known because lake scientist Jack Irwin and colleagues made surveys between 1967 and 1989 for the New Zealand Oceanographic Institute. Depth measurements (soundings) were made from a boat with an echo-sounder and equipment to locate the boat’s position.

Charts that show contours of depth in about 125 lakes are available in the New Zealand Lake Chart Series.

How lakes form

Few countries of comparable size have lakes of such diverse origins as New Zealand, where they are surrounded by mountains, glaciers, volcanoes and a complex coastline. The 775 lakes that are half a kilometre or longer have been classified according to how they formed:

  • 38% formed by glaciers (all in the South Island)
  • 16% by rivers
  • 15% by dunes
  • 8% artificial
  • 5% by landslides
  • 4% by volcanoes (all in the North Island)
  • 4% by coastal barriers
  • 10% other/unknown.

Turquoise Tekapo

Lake Tekapo is one of several glacial lakes with a distinctive blue-green colour. This is caused by tiny suspended particles (called rock flour) that have been ground off the underlying rock by glaciers.

Glacial lakes

Much of the higher country in the South Island was covered by ice during the glacial periods of the last two million years. Advancing glaciers eroded large steep-sided valleys, and often carried piles of moraine (rocks and soil) that acted as natural dams. When the glaciers retreated, they left basins that are now filled by lakes – for example, Manapōuri, Wakatipu, Wānaka, Pūkaki, Coleridge and Rotoroa. The level of most glacial lakes in the upper parts of the Waitaki and Clutha rivers is controlled for electricity generation.

Volcanic lakes

Volcanic lakes are largely confined to the Taupō Volcanic Zone and the area around Auckland. Lakes Taupō and Rotorua fill calderas – enormous volcanic depressions caused by the land collapsing after a huge eruption of ash. Other volcanic lakes are caused by explosive eruptions forming craters, or by lava flows and ash deposits blocking the drainage of rivers.

Other types of lake

River, dune, landslide and coastal barrier lakes are all formed by natural processes that change the drainage and cause water to pond up. When a river changes its course during a flood, part of the old channel is often left behind as a lake.

Lake Waikaremoana is dammed by an ancient landslide, and Te Waihora (Lake Ellesmere) is held in by a coastal gravel bar caused by strong northerly currents along the coast.

Artificial lakes

More than 60 man-made lakes have been created for power generation and water supply. For example a number of reservoirs have been formed by damming narrow valleys in the Waitākere and Hunua ranges, to supply water for Auckland.

The largest artificial lakes have been created to generate hydroelectric power. These include a chain of lakes on the Waikato River and many rivers in the lower South Island. Lake Benmore, on the Waitaki River, is New Zealand’s largest artificial lake, with an area of 74 square kilometres. Lake Rotorangi, on the Pātea River near Whanganui, is 46 kilometres long – New Zealand’s longest lake.


Lake processes

Lake level

The level of a lake reflects a balance between water coming into the lake (from rainfall, rivers and groundwater) and leaving it (from evaporation, seepage and outflow). Rainfall, ultimately the source of all water entering a lake, is usually highest in winter months. If a lake has no outlet, its level will rise and fall according to the rainfall. But with an outlet the level will stay stable, although the outflow will vary.

Levels at some major lakes have been recorded on some of the major lakes for up to a century. These are some of the most reliable water measurements in New Zealand. Today lake levels are recorded automatically at many sites, and this data is immediately radioed to central recording sites.

Seiches: oscillating water

Steady winds exert drag, which raises lake levels on the downwind side, and gravity depresses them in the opposite direction. In larger lakes this causes lake-wide fluctuations known as seiches. Levels on the shoreline gradually rise and fall by up to a metre. Each lake has a distinctive seiche period between high-water levels, ranging between 20 and 55 minutes. For example:

  • Taupō: 36 minutes
  • Wānaka: 39 minutes
  • Wakatipu: 52 minutes.

The lake environment

The apparent stillness of a lake conceals a complex environment. Although the water movement in a lake is weak compared to a river or the sea, it is of crucial importance for water quality as well as plant and animal life.

Water in a lake is always moving slowly under the influence of wind and the earth’s rotation. Small differences in water density can also cause water movement because denser water sinks below less dense water. Cold water is denser than warm water, and sediment-laden water from a flooded river is denser than clear water.

In contrast to rivers, which are constantly replenished by fresh water, lake waters are held in a basin, often for years or tens of years. Because the lake water is only slowly renewed, lakes are vulnerable to the effects of human activity, especially changes in the area that drains into the lake. Lake ecology and water quality are easily damaged, and may take longer to improve than in a river.

Long lost lake

Parts of Central Otago lie on lake silts. Geologists believe these formed in a large lake (named Lake Manuherikia), which existed 16–18 million years ago. Fossils show that the lake was home to water birds, fish, crocodiles and surrounding eucalyptus trees, and that the climate was much warmer then.

Water layers: spreading oxygen

For much of the year the waters of all but the smallest lakes have a distinct upper layer (epilimnion) and a lower layer (hypolimnion).

During spring and summer the lake surface is warmed by the sun. Wind movement keeps the epilimnion mixed, aerated and at a uniform temperature. This upper layer floats on the cooler, denser water of the hypolimnion. The two layers are separated by a narrow zone called the thermocline.

During autumn and winter the epilimnion cools and becomes denser. When it reaches the same temperature as the hypolimnion the water overturns and mixes. This annual event is critical for the life of the lake because it allows oxygen to be spread throughout the water. This affects all the plants and animals living there.

A giant’s grave

In Māori tradition, Lake Wakatipu is the grave of the giant Matau, who abducted a beautiful high-born woman, Manata. She had a suitor named Matakauri, who rescued her and returned to kill the giant, setting fire to the dried fern around him. Matau was suffocated by the smoke and, with flames licking at his side, he drew up his legs. His burning body, with raised knees, formed a distinctive curving chasm that filled with water. His heart continues to beat, causing the regular changes in lake level.

Sediment in lakes

Lakes act as a trap for sediment. Most of the sediment that is carried by rivers into lakes, or forms at the bottom when floating organisms (plankton) die, stays in the lake basin. Over time, a lake becomes shallower and eventually fills in. Most New Zealand lakes are young in geological terms – generally less than 10,000 years old.

Some glacial lakes have been repeatedly dug out as glaciers advanced, then gradually filled in with sediment during the interglacial period.

The annual rate of sedimentation in New Zealand lakes varies between 1 and 200 millimetres. The highest rates are in reservoirs (artificial lakes). These are on rivers that flow through highly eroded country, and carry a high sediment load.


Life in and around lakes

Lakes are home to waterfowl, fish and smaller invertebrates that live in fresh water or burrow in mud on the lake floor. Plant life is varied, including rooted and floating ferns, and flowering plants.

The food chain

Most lake life feeds on phytoplankton. These tiny floating organisms are mostly types of algae, diatoms and cyanobacteria that grow in the sunlit upper layers, where they make food by photosynthesis.

Phytoplankton are eaten by zooplankton (including minute rotifers, water fleas and copepods) as well as juvenile forms of larger animals. It is the beginning of a food chain leading to crustaceans, fish and waterfowl.

Underwater plants

Many plants are rooted near the lake shore. If there is adequate shelter, they grow like verdant underwater gardens. Some rooted and floating plants can survive at considerable depths, depending on the amount of light that filters through. The deepest known plants are a few species of bryophyte which have been found at depths of more than 70 metres in the clear waters of Lake Colerdige in Canterbury.

Shellfish and insects

The invertebrates (animals without backbones) that live in lakes are those that prefer water with little movement. The most obvious are freshwater crayfish or kōura, which grow larger than those in rivers. A variety of insects live in or on the water, including caddisflies, stoneflies, midges, mosquitoes and pondskaters.

Fish

Lakes and streams contain native fish (galaxiids), known to Māori as īnanga, kōaro and kōkopu, which do their best to stay hidden. The fish most likely to be seen are rainbow and brown trout, first introduced to New Zealand in the late 19th century. Both species of trout have thrived in the cool clear waters of most lakes, sometimes decimating galaxiid populations, but co-existing with other fish such as eels.

Footrot

Red-billed and black-billed gulls have nesting colonies around Lake Rotorua. They often gather around the lake’s thermal areas, enjoying the warmth in winter. You can spot a Rotorua gull that has lived there a long time, because the webs of its feet have become corroded by the warm, acid waters.

Waterfowl

The birdlife around lakes includes many birds found in other wetlands such as swamps and estuaries. Native birds that are only found in or near ponds and lakes include grey ducks and grey teal, and skilled divers such as the scaup, New Zealand dabchick (North Island) and crested grebe (South Island).

The larger birds are mostly introduced species, including mallard ducks, black swans and Canada geese. Other birds include the Australian coot and different species of shag.

It can be difficult to identify waterfowl at a distance. As a rule of thumb, ducks tend to favour open water whereas dabchicks, coots and grebes prefer the vegetation on lake margins.

Human impact: nutrient overload

Plant growth requires nutrients, especially soluble forms of nitrogen and phosphorus. These are naturally washed into lakes by streams and groundwater flow, but have greatly increased because of the impact of human activity, especially:

  • runoff from fertilised farmland
  • sewage and septic tank effluent (treated and untreated)
  • eroded soil from cleared land.

If the nutrient level is too high, there will be rapid growth of lake weed and algae, including toxic algal blooms. The decay of this excess plant material uses up the available oxygen in the water, and fish and other animals can die.

Ultimately a lake may become anoxic – lacking in oxygen – and effectively dead. This has been happening to many of the lakes near Rotorua, as well as lowland lakes such as Te Waihora (Lake Ellesmere) in Canterbury, since the 1950s.

Some exotic lake weeds, accidentally introduced, have thrived in lakes with unnaturally high nutrient levels. Piles of rotting African oxygen weed (Lagarosiphon major) around the margins of Lake Rotorua in the late 1950s were the first sign of nutrient enrichment that was obvious to the general public.


Recreation and other uses

Lakes are widely used for recreation – boating, fishing, swimming, waterskiing and enjoying the natural setting. Lakeside property is prized, and high prices are paid for homes with a lake view. Lakes Taupō and Rotoiti are popular holiday spots in the North Island, while Wānaka and Wakatipu are among the favourites in the South Island.

Fishing

Native eels are found in most lakes, especially shallow ones such as Te Waihora (Lake Ellesmere) and Lake Wairarapa. Eels were an important food source for Māori living nearby.

Because most native New Zealand fish are elusive, 19th-century settlers introduced brown trout (from England) and rainbow trout and salmon (from the USA) to offer better sport for anglers.

At first the trout thrived in New Zealand’s rivers and lakes, and became a major tourist attraction. But in the early 20th century it became clear that the size and health of fish was declining, especially in Lake Taupō and the Rotorua lakes. It appears that the rise in trout numbers lasted only until they had eaten the small native fish and insects in these lakes. The introduction of smelt (a small native fish) as a food supply, and restocking of some of the lakes with trout, has largely restored the fishery.

Fish and Game New Zealand is legally responsible for managing freshwater fisheries in most parts of New Zealand, which has been divided into 12 regions for that purpose. A licence is required for freshwater fishing, and the revenue is used to fund fisheries management. Although a licence may cover the whole country, each region has its own rules. A separate licence is needed at Lake Taupō, which is administered by the Department of Conservation.

Skating and curling

New Zealand winters are not cold enough for the larger lakes to freeze over, but smaller lakes and ponds sometimes freeze over in the southern South Island, and are used for ice skating.

The traditional Scottish sport of curling was introduced to Otago by gold miners, and nine clubs were established by 1900. Later, indoor skating rinks allowed New Zealand curlers to practise regularly, and to compete at international level.

Game-bird hunting

Game birds include several species of duck, shelducks, black swans and pūkeko, and several species of upland game such as quail, pheasant and partridge. The first weekend in May marks the traditional opening of the duck-shooting season, and is eagerly awaited by hunters. Major waterfowl hunting lakes include Wairarapa, Whāngāpē (Waikato), Te Waihora/Ellesmere (Canterbury) and Waituna (Southland).

A hunting licence from Fish and Game New Zealand is required, as all gamebird management is funded from licence fees. As with fishing there are 12 regions, each with their own regulations (with local variations about dates and bird species).

All game birds belong to the Crown until legally taken by a sportsperson with a valid licence. Birds must be shot on the wing, and not on the water.

Boating

Boats of all types, from steamers to yachts, kayaks and fizz boats, are used on lakes for recreation or transport. Before roads were built, boats were a significant form of transport. The SS Earnslaw was first used in 1912 on Lake Wakatipu, ferrying sheep, cattle and passengers, and continues as a tourist attraction based at Queenstown.

Several lakes are used for rowing, and there are world-class facilities at Lake Karapiro (Waikato) and Lake Ruataniwha (South Canterbury).

Conservation issues

After the Second World War a shortage of electricity led to the building of hydroelectric dams on rivers and lakes throughout New Zealand. Most of the major river systems were affected, including the Clutha, Waikato and Waitaki rivers. By the late 1960s there was growing concern about the rapidly decreasing number of unmodified rivers and lakes.

There was widespread public protest about a plan to raise the level of Lake Manapōuri (in Fiordland National Park), to provide electricity for an aluminium smelter. The project was dropped in 1972 after a change in government.

A chain of hydroelectric dams and artificial lakes was also planned along the Clutha River. In 1993 the Clyde Dam was filled to form Lake Dunstan, flooding apricot orchards and part of the town of Cromwell. Since then no more large hydroelectric dams have been built.


Ownership and control

The Treaty of Waitangi

The legal situation regarding the ownership and control of lakes in New Zealand is complex. Because of conflicting interests (such as tourism, boating, fishing, hydroelectric power and property development), it has been the subject of debate and litigation since the Treaty of Waitangi was signed in 1840.

By 2007 there was general acceptance that lakes are covered by Article Two of the treaty. This guaranteed Māori exclusive rights to ‘forests fisheries and other properties’ (English version) or ‘taonga’ in the Māori version (which could be translated as ‘treasures’). However, the treaty did not guide government policy regarding lakes.

Ownership of the lake bed

In British eyes, signing the Treaty of Waitangi brought New Zealand under the jurisdiction of the Crown, effectively governed by English common law. There are two significant points about English common law as it applies to fresh water, especially lakes:

  • The ownership of water is vested in no one. It is seen in the same way as air – a property in common ownership – although the Crown can manage its use.
  • Land beneath water belongs to the owner of the surrounding land. A single owner of land around a lake owns the lake bed. With multiple owners, ownership of the lake bed is generally split. This was not clear-cut for larger, navigable lakes, and was debated between Māori claimants and the Crown.

In the late 19th century there was a strong feeling that waterways should not be privately owned in new colonies. Instead of following English common law, the New Zealand government vested ownership of all navigable rivers in the Crown – but this did not include lakes.

In cases that came before the Māori Land Court, there was strong evidence of Māori ownership and traditional use of lakes. The Crown was forced to negotiate with owners of the lakes that it wished to obtain title for. Ownership issues have therefore been settled individually on an ad hoc basis. The ownership of only a small number of lake beds has been clearly settled, each after lengthy negotiation and special legislation.

Ownership of Lake Taupō

The territory of the Ngāti Tūwharetoa people is around Lake Taupō, and the lake has long been a major food source. The Crown refused to recognise tribal ownership, and in 1926 passed a law making the lake bed the property of the Crown. In return the Ngāti Tūwharetoa Trust Board received an annuity and a sum equivalent to 50% of the gross revenue from the sale of fishing licences.

But debate continued over the control of the lake. For example, the lake outlet was altered for hydroelectric development without consulting the tribe, and water from the Tongariro power scheme was diverted into Lake Taupō.

In 1992 the Crown returned the ownership of the bed of Lake Taupō to Ngāti Tūwharetoa. This has been a model for resolving Māori land claims about lakes. The settlement does not change public rights of access, navigation or fishing, but is seen as recognition of Ngāti Tūwharetoa’s traditional tribal authority (mana whenua) over the lake.

In 2006 the ownership of the beds of many Rotorua lakes was vested in the Te Arawa Lakes Trustees in a similar agreement.

Control of water use

Although water is regarded as common property, its use has been regulated to ensure that one individual or group does not adversely affect others. Under the Resource Management Act 1991, the management of water resources is the responsibility of regional and unitary councils, with a long-term goal of sustainability.

Maintaining or improving the water quality of lakes is of particular concern, as many lakes have shown an alarming deterioration since the 1950s.

Lakes have high value for fishing, and most have been stocked with trout. Except for those in the Rotorua area, the trout fisheries are now self-sustaining. Fish and Game New Zealand controls fishing (including restocking and the collection of licence fees) in all lakes except Lake Taupō, which is administered by the Department of Conservation.

Acknowledgements to Neil Deans (Fish and Game New Zealand) and David Lowe (University of Waikato)


External links and sources

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How to cite this page: Simon Nathan, 'Lakes', Te Ara - the Encyclopedia of New Zealand, http://www.TeAra.govt.nz/en/lakes/print (accessed 18 July 2019)

Story by Simon Nathan, published 24 Sep 2007