Restoring Rotorua’s natural geothermal taonga
The haukāinga (local residents) of the Rotorua area – Te Arawa, Tūhourangi and Ngāti Wāhiao – have lived in this highly active geothermal region for generations. The unique geology of the area shaped the way they live, and they used the geothermally heated water for cooking, bathing and heating.
Cooking with geothermal heat
Hot pools provided a means of cooking and preserving food. They were also used for bathing and washing.
These traditional uses had little impact on the geysers and hot pools. As Rotorua’s fame grew in the early 20th century, tourists visited Rotorua to experience the sites and smells of its geothermal field. The lure of geysers, boiling mud pools and the opportunity to soak in warm, thermal pools was appealing. Also appealing was the use of geothermal water to inexpensively heat homes, hospitals, schools and businesses. By the 1980s, 30,000 tonnes of water were pumped from the geothermal aquifer every day.
Rotorua geothermal field: protecting a taonga
Rotorua is world famous for its geothermal features. For generations, local Māori used the hot pools with little impact on the natural system. As Rotorua’s population grew, unsustainable amounts of water were pumped from the geothermal aquifer, and geysers and hot pools dried up. In this episode of Project Mātauranga, GNS scientist Brad Scott and local Māori explain how the decision to close hundreds of bores has led to the resurgence of geothermal activity.
Kei te whakamahia te mātauranga o te hau kāinga me te mātauranga pūtaiao kia mārama ai ki te nui o te tauwhirotanga. (Local knowledge and scientific methods have been employed to ascertain how great the change has been.)
Dr Ocean Mercier
Activity idea – Rotorua caldera
The Rotorua geothermal area was formed by a massive caldera. Watch the Rotorua caldera formation animation then go outside and conduct the student activity Calderas in the sandpit.
Lake Rotorua
Lake Rotorua is a caldera volcano that erupted about 240,000 years ago. The eruption caused the mountain to collapse, and the hole has since been filled by water, forming a lake. The eruption was followed weeks later by an explosion at Ōhakuri.
Acknowledgement: GeoNet
Te take – using geothermal water as a power supply adversely affected the system
In other parts of the Taupō Volcanic Zone, large volumes of water were being extracted for electricity production. As a result, geysers near the Wairākei power station disappeared and other geothermal features declined. There were concerns that the same thing would happen to the Rotorua field.
Monitoring systems in the Rotorua area were set up in 1982. The results showed a 30% decrease in heat flow and the loss of many geothermal features. Springs and pools dried up, and geysers became dormant. Experts speculated the 1,000 shallow bores around Rotorua were reducing the geothermal aquifer. GNS scientist Brad Scott uses a garden hose analogy to explain what was happening. “If you think of each bore as a hole in a hose, eventually less water is going to come out of the sprinkler at the end of the hose.”
Activity idea – Aquifer systems
An aquifer is a layer of permeable rock or sand that contains water. Precipitation or other water sources soak into the ground, recharging the aquifer. Watch Brad Scott in the GNS YouTube video Geothermal Features – an Introduction as he describes the geothermal aquifer and the features it supports, then make your own aquifer model.
Building an aquifer model
In this video, educator Angela Schipper demonstrates how to build a model of an aquifer – a layer of rock or other material that carries water underground. This is an excellent activity that needs only a few easy to organise resources.
Point of interest
Teachers may want to ask students why the water does not simply disappear in the ground. (Not all rock layers in the ground are equally porous – some are impermeable).
Nature of Science
Scientists make use of models to test predictions. Models allow scientists to test a range of scenarios. without potentially harming the environment.
Te whāinga – to restore geothermal features by restricting bore use
In the late 1980s, all bores within a 1.5 km radius of Whakarewarewa’s Pōhutu geyser were required to close. This was a controversial decision. Many locals had spent considerable money having bores drilled, and some local marae were unable to continue with their traditional cooking methods. The number of bores dropped to 140, and less than 3,000 tonnes of water was removed from the geothermal aquifer daily.
High-water mark
The high-water mark on the silica terrace shows how the water level has dropped in the Whakarewarewa thermal system.
Closing the bores has made a significant difference. By 2015, nearly 60% of Rotorua’s geothermal features had recovered, with a further 15% showing some activity. For example, previously dry Kuirau Park hot pools are filled with water again. The Papakura geyser, silent for nearly 35 years, is spouting water and steam. Brad Scott recognises that it has taken several decades for the features to recover, but he is excited by the 40-year experiment’s success. This type of restoration is unique – it has not been done anywhere else in the world.
Observation – mātauranga meets science
The partnership between GNS Science and local Māori shows the value of combining mātauranga Māori with modern science practices. Brad uses traditional scientific methods like water temperature and flow rates to monitor geothermal systems. Local Māori who live and work in Whakarewarewa and Te Puia monitor the features as part of their day-to-day activities. Te Arawa Lakes Trust strategic manager Roku Mihinui comments, “These interactions consolidate the information and allow scientists to be more confident in their predictions.”
Activity idea – Observation
Observation is fundamental to scientific investigation. Brad Scott and other scientists use tools to measure changes in the geothermal features, but more simple observations are also important – the high-water mark on a hot pool indicates changes to water levels in the pool.
Scientific observation is a skill that students need to practise. Read the article Observation and science and then try one of these observation activities: Observation: learning to see – harakeke and Observing earthworms.
Nature of science
Observations yield data. Scientists analyse and interpret data, including observations, in order to understand how the natural world works. Data derived from geothermal measurements – as well as visual observations from locals – helped inform Brad Scott’s research.
Useful links
"World's best" – in August 2024 Rotorua’s geothermal fields (Ahi-Tupua), Mount Ruapehu Volcano, Muriwai megapillow lava flows, the towering sea cliffs of Fiordland and Maruia Falls made the International Union of Geological Sciences list of The Second 100 IUGS Geological Heritage Sites.
Visit Te Ara to learn more about Hot springs, mud pools and geysers.
The New Zealand Herald/Rotorua Daily Post website has video, images and text about the renewed geothermal field in the New Zealand Herald article Giants stir beneath the earth.
In November 2016, a 30 metre-high geyser erupted from the lake shore near Rotorua's Ohinemutu Village. Brad Scott explains the origins of this short-lived geyser and other hydrothermal eruption craters in this New Zealand Herald article.
Project Mātauranga
Watch Series 2/Episode 4: Rotorua Geothermal Field: Protecting a Taonga
Project Mātauranga is a television series that investigates Māori world views and methodologies within the scientific community and looks at their practical application. Each of the 13 episodes in series 2 shows how western science and Māori knowledge systems are combining to provide solutions to a variety of challenges.
The Science Learning Hub thanks Scottie Productions for allowing us to host these videos.
Scottie Productions
Scottie Productions is an independent production company established in 2005 by owner and director Megan Douglas.
