Immediately south of Lake Taupō within the small village Tokaanu some hot springs, mud pots and one geyser form the Tokaanu Thermal Area. It is a popular destination but far from being crowded with tourists. Almost like regular ponds most of the hot springs are closely framed with trees, while only a little bit of steam and some colourful mats of thermophilic mircroorganisms indicate their true nature. Alone the geyser and two or three of the hot pools give you the faint impression of being in a thermal area. Tokaanu Thermal Park is of scientific interest particularly because many of the springs come with a long history of sinter deposition.
The natural hot springs motivated the Ngati Tuwharetoa to settle down in this place more than 500 years ago. Up to the early 20th century the springs were embedded in a large open sinter flat. The geysers Te Korokoro a Te Poinga, Te Pirori and one or two unnamed ones occupied a bushy area adjacent to the north. For 1942, S.H. Wilson reported an unnamed geyser, spouting 13 m (43 ft) high at an interval of 30 minutes (Mahon and Klyen's Spring 25, next to the current car park), which was thereafter extinguished by raising the lakes water level for hydroelectric development (Proc. Second United Nations Symposium on the Development and use of Geothermal Resources, Volume 3, San Francisco, USA, 1975, p.2462).
Monitoring of hot spring activity since the 1880s revealed a strong and almost constant decline in hot springs' temperatures and discharge rates. Accordingly, the once very extended, exposed sinter deposits have shrunk significantly by overgrowing and formation of bogs. A lucid survey of these developments and the historical names of the thermal features can be found in M. Hochstein, H. Keys, R. Keam, Decline in rate of (silica) sinter deposition in the Tokaanu Domain, Lake Taupo, (NZ); Proc. 30th NZ Geothermal Workshop, 2008.
On a clockwise walk you first pass a spring north of the trail named Te Waihoto, but there is little more to see but wet ground covered by dead branches. Past Te Waihoto you reach the southeastern corner of the thermal area where the only currently active geyser on location is to be found. The geyser site is private ground and usually separated by a fence. On our visit the area was open and we could catch a glimpse of the feature. Taumatapuhipuhi (Frequently Blowing Hilltop) features an andesite chasm filled with crystal clear hot water. The rim shows only minor sinter deposits. A carved channel drains hot water in a northward direction to a private cooking area. B.Y. Lynne stated in Monitoring of Geothermal Features, Environment Waikato Technical Report 2009/25, that Taumatapuhipuhi spouted to more than 30 m (>100 ft) height in the 19th century (source missing), whereas recent observations give evidence of up to 1.5 m (5 feet) high eruptions every 1-5 min. We waited approximately 20 minutes and saw it splashing to less than one foot height every minute or so.
From Taumatapuhipuhi the trail curves in western direction around Matewai Spring. The first viewpoint is near Matewai's runoff area with extended yellow mats of thermophilic organisms.
Runoff of Matewai
The very spring can be better spotted from the west, where the trail separates it from its western neighbour, Hoani. Matewai is one of the few springs at Tokaanu which at times exceed 90 °C (194 °F) surface temperature. Lynne reported eruptions of up to 4 m (13 feet) height over 4 months in early 1982 and of 2 m in early 2003, thus confirming similar, less recent observations by earlier authors. Around 2008 an adjacent pool emerged, so today Matewai is composed of two pools separated by a submerged rock ledge.
Across the trail from Matewai abundant steam blurrs the view to Hoani. This and the bright colour already indicate that Hoani is quite hot, too, often well above 80 °C (176 °F). Hochstein et al. referred to occasional ebullient eruptions in the first half of the 20th century. I could find no evidence for geyser activity thereafter, though.
On the picture above a further spring beyond Hoani is hardly recognisable through the dense steam. According to the information board at the site entrance this is Kirihoro, whereas it is denoted as Hoani B Pool in current scientific papers. In general it is not only smaller but also less hot and less active than Hoani / Hoani A Pool. This trend continues with Hoani C Pool, which is almost completely obscured from the trail.
Unfortunately, the naming of springs in the Tokaanu Thermal Area is quite inconsistent because in the past on more than one occasion names have been switched between features. Sometimes also different spellings or identifiers have been used. This does not only apply to Hoani, but even more to some of the following spings. However, the next two features don't have this problem because they are unnamed. The first one is in an area south of the trail denoted as "Mud pools and mud volcanoes" on the information board. On our visit it was nearly dried up.
Tokaanu mud volcanoes
A larger pool farther west with chocolate brown water is also part of the mentioned mud pools and mud volcanoes. This pool and the next three westerly adjoining springs were still at boiling temperature at the end of the 19th century. It can be suggested that its appearance was substantially less muddy in those days and that it was surrounded by an open sinter area instead of trees.
Tokaanu mud pools
The label "Original hot pools bathing area" on the information board indicates not a position in its own right on the map like the other labels, but refers to the yellow box in centre, which may be a little bit misleading. In this centre area two large depressions collected discharge water mainly from the Te Paenga Pools in the south, and were used for bathing between 1875 and 1913. In 2007 the overflow of Te Paenga springs ceased and the bathing area ran dry. Currently, dense vegetation obscures all features in this central spot almost completely.
Takarea, located north of the trail, has suffered the same decline in temperature and discharge as all other springs in this section.
South of the trail two further springs show up, called Te Paenga Pools by Hochstein et al.. For each, the same decline applies as for Takarea. In the Environment Waikato Technical Reports these springs are called Takarea 5 Pools (east and west), while the above mentioned Takarea Spring is called Takarea 6 Pool. The information board on location assigns the name Takarea to Hochsteins Te Paenga East Pool. Here the above mentioned inconsistency in names becomes very apparent.
To the west the next two pools are Toretiti north of the trail and Te Ngutu south of it. In this case I only use the Hochstein nomenclature and will not go into the available name variants. Both pools have clearly seen better days, their current temperatures typically range between 30 °C and 50 °C (86-122 °F).
The series of springs gets interrupted by a few slightly bubbling mud pots south of the trail past Te Ngutu Spring. They are small and not very spectacular, so I pick only the largest of them as an example.
The southwestern corner of Tokaanu Thermal Park is occupied by the large Paurini Spring. A short turning of the trail leads to the viewpoint. Already the steaming and the deep green colour indicate that it is a little bit hotter than the springs described before. Indeed, its temperature is usually around 60 °C (140 °F), but like other pools around once it was a boiling hot spring.
In the west beyond Paurini and outside the area of the thermal park two bore holes are located. They were drilled in 1942 to a depth of around 100 m (320 feet) and supplied hot water but were sealed shortly after. However, the seal of the southern hole, BH-2, was damaged, and from the 1950s on BH-2 has acted as a spouter and has built up a large sinter mound. The feature is not accessible to tourists, though.
On the loop trail back from Paurini to the car park Teretere is the only named spring along the complete northern border of the area. If the reed-lined spring visible north of the trail really is Teretere (hard to estimate with the available maps), then it has cooled down to such an extend that now frogs feel comfortable in it.
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