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.
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.
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 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.
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.