Classifying geothermal systems

Classifying geothermal systems by natural values •
Classification and management •
Classification of our major geothermal systems •
Taupō Volcanic Zone Geothermal Systems

Classifying geothermal systems by natural values

We can classify our geothermal systems by their natural values. Classifying our geothermal systems helps us determine the most suitable management approach for each system.

Surface features of a geothermal system may be:

an isolated feature (a hot spring or mud pool, or geyser or area of steaming ground)
a set of features grouped together
several sets of features fed by a single upflow (a geothermal field).

When activities on one geothermal field (such as water extraction) affect another field, the fields are regarded as parts of the same geothermal system. For example, the Wairakei-Tauhara system is made up of the Tauhara and Wairakei fields.

The system itself includes:

a body of geothermal water
material containing heat or energy surrounding the water
all plants, animals and features dependent on it.

Check out our map of geothermal systems in the Taupō Volcanic Zone, below.

Classification and management

Increased pressure to develop and use geothermal resources prompted Environment Waikato to classify the Region’s geothermal systems into five categories:

Development
Limited Development
Research
Protected
Small.

Classification is based on ranking each system’s characteristics and aims to balance development with the protection of highly valued surface features. There is a different management approach for each category.

In areas classified for Development, large-scale uses are allowed as long as they are undertaken in a sustainable and environmentally responsible manner.

In Limited Development systems, takes that will not damage surface features are allowed.

Research systems are those where not enough about the system is known to classify it as either Development, Limited Development, or Protected. In these systems, only small takes and those undertaken for scientific research into the system are allowed.

Protected systems contain vulnerable geothermal features valued for their cultural and scientific characteristics. Their protected status ensures that their underground geothermal water source cannot be extracted and that the surface features are not damaged by unsuitable land uses.

Small systems are isolated springs or sets of springs. These can only sustain small takes and are not suitable for electricity generation.

Classification of our major geothermal systems

Select a tab

Development geothermal systems
Limited development geothermal systems
Research geothermal systems
Protected geothermal systems

Development geothermal systems

System	Reason
Horohoro	Few surface outflows vigorously depositing sinter. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.
Mangakino	Few surface outflows vigorously depositing sinter. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.
Mokai	No surface outflows vigorously depositing sinter. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.
Ngatamariki	No surface outflows vigorously depositing sinter. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.
Ohaaki	Existing surface features significantly impaired by legally established large takes. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.
Rotokawa	Few surface outflows vigorously depositing sinter. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.
Wairakei - Tauhara	Existing surface features significantly impaired by legally established large takes. No evidence of a flow of subsurface geothermal fluid to or from a Protected Geothermal System.

Limited development geothermal systems

Research geothermal systems

System Reason

Reporoa Several surface outflows vigorously depositing sinter. May be hydrologically linked to Waikite-Waiotapu-Waimangu Geothermal System.

Large systems as yet undiscovered

Protected geothermal systems

Taupō Volcanic Zone Geothermal Systems

Most of the Waikato region’s geothermal resource is actually underground. The geothermal activity we can see on the Earth’s surface is much more restricted in size and distribution. One way of determining the extent of geothermal systems is by measuring the ground’s electrical resistivity.

This GNS DC resistivity interactive map shows the geothermal systems in the Taupō Volcanic Zone as they are defined by electrical resistivity.

Resistivity is a measure of the ground’s ability to conduct electricity. Generally, geothermal water has lower resistance (conducts electricity better) than normal ground water.

Low resistivity (red) indicates the presence of geothermal water.
High resistivity (purple) indicates normal ground water, soil and rock.

System	Reason
Atiamuri	Several surface outflows vigorously depositing sinter, and other moderately to highly vulnerable features, that would be adversely affected by large takes, but which are unlikely to be adversely affected by small to medium-sized, suitably located takes.
Tokaanu - Waihi - Hipaua	Many geysers, sinter-depositing springs, geothermal habitats, mud pools, and other vulnerable surface features, that do not appear to be significantly adversely affected by the many small to medium existing extractions. Limited new extractions may be accommodated without adverse effects on the Significant Geothermal Features but larger extractive uses would be likely to have significant adverse effects.

System	Reason
Horomatangi	Sinter-depositing springs on the bed of Lake Taupo, sinter tubes and associated specialised ecosystems.
Orakeikorako	New Zealand's largest concentration of geysers, sinter-depositing springs and other moderately to highly vulnerable geothermal features. Significant populations of Cyclosorus interruptus, Schizaea dichotoma, Christella dentata, and Nephrolepis cordifolia.
Te Kopia	Rare mud geyser (which may be a chloride geyser), several mud pools and super-heated fumaroles, large area of geothermal vegetation that represents the best quality example of a relatively intact area of geothermal vegetation which is part of a high quality ecological sequence. Contains the at-risk geothermal plant species Dicranopteris linearis, Calochilus paludosus, and C. robertsonii. May be hydrologically linked to Orakeikorako Geothermal System.
Tongariro	Is mostly within Tongariro National Park, a World Heritage Area.
Waikite - Waiotapu - Waimangu	Many geysers, sinter-depositing springs and other moderately to highly vulnerable geothermal features. Significant populations of Cyclosorus interruptus, Christella dentata, Dicranopteris linearis, and Nephrolepis cordifolia.

Classifying geothermal systems