How we monitor
Waikato Regional Council has a routine monitoring program for geothermal areas. This tells us the activity status of geysers and sinter depositing springs at selected geothermal fields.
You can find out more information on these sites, including photographs, using our monitoring sites map.
We monitor annually at the selected geothermal fields. We monitor quarterly at Ngatamariki, Orakei Korako, Tauhara, Te Kopia, Tokaanu, Waikite Valley and Waiotapu, as these fields are considered especially vulnerable to change or damage.
- Historical data are taken from records collated from about 1930 to 1995.
- Current data are taken from Waikato Regional Council’s monitoring programme since 1995.
Waikato Regional Council commissioned research to collate all known records of geothermal activity in the region prior to 1995. Earliest records date from the 1930s.
Monitoring is carried out by visual inspection and then comparison is made to photographic records of previous years. The status of a spring or geyser is based on the expert judgement of the monitoring officer. Sometimes this is based on anecdotal evidence, particularly for geysers that erupt infrequently (eruptions may not be witnessed by the monitoring officer).
Waikato Regional Council uses the following assessment of geothermal features in this indicator:
Sinter depositing springs generally produce neutral to alkaline fluids of deep geothermal origin at or near boiling temperature. The water contains a high concentration of silica or calcium carbonate, which precipitates to form sinter. The springs are chemically distinct from shallow hot springs, which produce water with few geothermal contaminants that has been heated either by steam or by contact with hot tectonic rocks. Acidic springs can also dissolve and deposit sinter, but usually to a far lesser degree than alkaline springs.
Many sinter springs have been significantly modified by human activities, for example channelling of outlets, and as a result natural sinter deposition (in terraces) is no longer occurring in many springs. However, where sinter is being deposited in the drainage channel, the spring is classed as depositing sinter for this indicator, reflecting the chemistry of the spring, not the physical drainage characteristics of the surrounding geology.
Geysers are considered to be hot springs which boil and throw out steam and water with a repetitive cycle of alternating calm and eruption. The intervals between eruptions can vary over minutes to hours or days, as also can length of the eruptions. However, there is usually some regularity or predictability involved in their behaviour.
Geysers listed as active are those which have been active in the past 20 years. Others have very extended periods of inactivity lasting many years and have been excluded from this list. Inactivity of geysers may be due to natural variations in the supply of fluid or the geyser's upflow channels.
Alternatively their inactivity may be due to human interference with the parent geothermal systems by reducing feed pressure and water levels until geysers can no longer function. Wairakei, Tauhara, Tokaanu, Ohaaki and Orakei Korako have all lost geysers due to humans making physical changes to those systems.
This indicator is compiled from the results of our routine monitoring program for geothermal areas. Data are presented as the total number of springs actively depositing sinter, or the total number of active geysers.
Historical (about 1930 to 1961) data, including two major events which resulted in the loss of large numbers of springs and geysers in the region (Wairakei, 1958 and Ohakuri, 1961, power station developments), is compared with current status (activity since then). Although this represents a disproportionate time period for comparison, the historical data are intended to present a baseline to compare with future indicator updates.
Trends in geyser and sinter spring activity are calculated as a percentage of new or lost sinter depositing springs or geysers.
This indicator is based on periodic visual inspection of sites and anecdotal evidence. It is a ‘snap shot’ of activity and may not detect geyser activity occurring at other times.
There are a number of geothermal features that are inaccessible, or have yet to be monitored. Therefore, this indicator does not represent the complete suite of geysers and sinter depositing springs in the Waikato region. There are no plans to undertake more detailed surveys in order to locate and describe features not captured in the scope of this indicator.