Story: Volcanic Plateau region
Page 11 – Geothermal and hydroelectric power
The Volcanic Plateau is notable for the large hydroelectric power stations on the Tongariro/Waikato River, but the most distinctive source of electricity is geothermal.
Geothermal springs – early uses
Heat from the geothermal springs and waters had long been used by Māori. In 1869, geologist Ferdinand Hochstetter described separate springs for bathing, cooking and laundry, and vapour baths and winter huts that had been built on the warm sinter terraces. Especially in winter, the baths were communal meeting places.
The potential of drilling for hot water and steam had first been demonstrated in Italy, and began in New Zealand in the 1930s, through bores reaching water or steam, which rose or could be pumped to the surface. By 1946 there were over 300 bores in Rotorua alone.
The first geothermal power station, at Wairākei, near Taupō, was completed in 1964, and a second opened at Ōhaaki in 1989. Wairākei generates 190 megawatts of power and Ōhaaki has a capacity of 108 megawatts.
Drawing off geothermal steam and water for power has reduced natural geothermal activity. The Wairākei station ended most geothermal activity there and at the nearby Spa field. The hydroelectric development at Ōhakuri on the Waikato River stopped most activity on the Ōrākei Kōrako field. Many scientists welcomed the research opportunities opened up by geothermal development, but others were more cautious, and locals were anxious about the impact on tourism. A controversial campaign in Rotorua in the 1980s saw bores closed to ensure the survival of some geothermal areas.
Ted Lloyd worked for the Geological Survey in Taupō and Rotorua for many years, and with physicist Ron Keam argued for managing power development to preserve some natural geothermal activity. Of Wairākei Ted said, ‘There is a total disaster there, isn’t there? All the geysers in the Wairākei field are dormant – defunct – they will probably never erupt again.’ 1
Interest in exploiting geothermal resources has been revived in the last few years, although there are now strict requirements for waste disposal. New methods make it possible to find previously unidentified hot water resources. Three new power stations have opened since 1995 at Rotokawa, Mōkai and Poihipi, all near Taupō.
The earliest hydroelectric power station in the region, at Ōkere Falls on the Kaituna (Ōkere) River, supplied power to Rotorua from May 1901. It was the fourth town in the country to have electricity. Around Lake Taupō, the first hydroelectric station was built at Waihī Falls, and later ones on the Hinemaia River (1952) and Kuratau River (1960).
Work on harnessing the power of the Waikato River began in the 1920s at Arapuni. Damming of the middle reaches of the river began after the Second World War. Dams were built at Aratiatia, Ōhakuri, Ātiamuri, Whakamaru, Maraetai and Waipapa. The 360-megawatt Maraetai dams generate the most power.
The Tongariro scheme, harnessing the waters of the Whanganui, Rangitīkei and Waikato/Tongariro river catchments, began in the 1960s. It involved diverting the headwaters of several catchments, often through massive tunnels, into the headwaters of the Tongariro River and to Lake Rotoaira. Electricity was generated through power stations at Rangipō and Tokaanu, which produced 120 and 200 megawatts of power respectively.