Lake Ohakuri, at 12 km², is the largest artificial lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 of the Waikato

Waikato

The Waikato Region is a local government region of the upper North Island of New Zealand. It covers the Waikato, Hauraki, Coromandel Peninsula, the northern King Country, much of the Taupo District, and parts of Rotorua District...

 river system in 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...

. It forms the reservoir for the Ohakuri hydroelectric power station. Construction of the dam, approved in 1955, began in 1956 and was completed in 1960. The lake was filled over 14 days in January and February 1961. This drowned two thirds of the Orakei Korako

Orakei Korako

Orakei Korako , is a highly active geothermal area most notable for its series of fault-stepped sinter terraces, located in a valley north of Taupo on the banks of the Waikato River in the Taupo Volcanic Zone, New Zealand...

 geothermal area, including two of the world's largest geyser

Geyser

A geyser is a spring characterized by intermittent discharge of water ejected turbulently and accompanied by a vapour phase . The word geyser comes from Geysir, the name of an erupting spring at Haukadalur, Iceland; that name, in turn, comes from the Icelandic verb geysa, "to gush", the verb...

s, Minginui Geyser and Orakei Korako Geyser.