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.
Transcript
Dr Ocean Mercier
Māori have always been scientists, and we continue to be scientists. Our science has allowed us to live, work and thrive in the world for hundreds of years. My name is Dr Ocean Mercier, and I’m a lecturer in pūtaiao Māori at the Victoria University of Wellington. My job takes me all over the world to talk about Māori science and how traditional knowledge is being married with western science here in Aotearoa in order to find innovative solutions to universal global issues.
In this programme, we are going to show you how these worlds of science are intersecting and how the paths to our future are being formed.
The Rotorua geothermal field lies under both the city of Rotorua me te pito whakatetonga o te moana o Rotorua (and the southern end of Lake Rotorua). It’s unique on a world scale, made even more so because Te Arawa, Tūhourangi and Ngāti Wāhiao people have lived amidst the boiling geysers and pools for generations, me te aha, nā aua waiariki kua muia rātou e te hunga tūruhi (and tourism has thrived here because of it).
But in recent years, overextraction of the geothermal fluid has taken a huge toll, and many geysers, pools and springs have dropped off or in some cases even disappeared. Haukāinga and scientists are now joining forces to monitor what is happening and to work out a plan to better manage and protect the geothermal field.
Kei te mahi a Brad Scott mā Pūtaio GNS hei kaimātai puia, ā, kei te mahi tahi hoki a ia ki ngā tāngata o Whakarewarewa kia mārama ai ia ki ngā papa waiariki, otirā, kia ora tonu ai aua papa. (Brad Scott’s a volcano surveillance co-ordinator for GNS Science and has been working with the people of Whakarewarewa to better understand and preserve the system.)
Brad Scott
Rotorua city and in particular the Whaka and Ohinemutu villages are really quite unique globally. I’m not really aware of anywhere else with such a high concentration of people living on top of a geothermal system and in and amongst the system. The reason that we have some really large-scale geothermal systems in the Rotorua/Taupō area, in particular, here we are in Rotorua, is we’ve also got some really large-scale volcanism. It’s a special type of volcano called a caldera. They erupt somewhere between 50 and 200 or 300 cubic kilometres of rock, and they leave behind an enormous body of hot rock in the ground. That body of hot rock – just think about it like an electric element on the stove – basically, what we will have underneath here is just a plume of hot water rising from the hot rock. So it’s been heated up just like a pot sitting on an element, that water’s been heated, it’s creating steam, and it’s just rising up through the rocks that are underneath us and reaching the surface where it finds an easy way to get to the surface, and it creates what we call a surface expression of a geothermal system. So that’s the surface part, and the piece underneath us really is just hot water and steam inside the rock.
Ringahora Huata
Although we utilise our natural resources – bathing facilities – men, women, children communally, so that means aunties, uncles, cousins, nephews and nieces utilising our resources – it’s a lifestyle that many people would pay a lot of money for.
Ngamoni Huata
With the new mums that have their babies, they’re able to sit on these seats here, get the baby and bathe the babies. And by sitting there, they get used to the water as well. This one here’s got mud silt. We used to have the spa baths where tourists used to come in the early 1900s, that’s been shut down now. That’s with sulfur and all that too, so that sulfur, it’s about the healing waters. And the Whaka bath up the top there, those are the oil baths, very oily to the touch, so you don’t even need soap because of the oils and the minerals within the water. So we have three baths, and we can say “Go up to the top bath” or “I’ve got this…”, “Go down to the bottom bath”. So it’s about understanding and knowing the different qualities of the water.
John Waaka
Well, it gives me my beautiful complexion, that’s all I can say. But arthritis or rheumatics – the old people used to take the baths and feel 100% better, and they would use those baths that we couldn’t get into – it’d be so hot, we couldn’t get into it as kids – but they’d get into it, and it’d be almost boiling hot, but they’d get out and they’d be really fixed, and all their aches and pains would be gone.
Brad Scott
In the 1950s, New Zealand pioneered the production of electricity from geothermal systems. And we didn’t really think too much about the consequence, and as we developed Wairākei, and the spa and Ōhākī, Broadlands area, Kuirau, we realised that we were actually trashing the surface features and were destroying the surface features of our geothermal systems. And all of a sudden people realised that “Oh, we’ve had 150 geysers, we’ve only got five or six left.” So all of a sudden, a whole pile of value was placed on the surface geothermal features, and there was a big swing from development to conservation.
Dr Ocean Mercier
I roto i ngā tau rua tekau, toru tekau rānei, kua tino kūtere mai ngā tūruhi ki konei, ana, kua maha ake ngā hōtera me ngā ngote waiariki o roto kua tino mimiti haere ngā waiariki, ā, kei te tino māharahara te haukāinga me ngā kaipūtaio ki tērā. (In the past 20 or 30 years, tourism has boomed, hence more hotels and bores, and there has been an alarming drop in geothermal activity – something that equally concerned locals and scientists.)
Roku Mihinui
Yeah, the first real impact we had was for us down at the Roto-o-tamaheke, which feeds our Hīrere bath or the waterfall bath, and the water level dropped so low that there was no free flow of the water. We created some drains to try and offset the low level, but it didn’t work to a great extent. And we noticed at the same time that it was occurring with what we used to call the Blue Lake, which was a big lake that, in its deepest part, was around about 15 feet – that sat below the Pōhutu geyser in the background. You might be able to see the high-water mark still showing on the silica terraces there.
Brad Scott
One of the consequences of developing geothermal energy is that you take the fluid out of the ground rather than allowing it to come to the surface to feed the hot springs. And the analogy I use for it is a hose feeding a sprinkler. You have a garden hose and you have a sprinkler, and if you think of each drillhole as being a hole in that hose, eventually less water is going to come out of the sprinkler and therefore there is going to be less springs. And that’s really the crux of what happened in Rotorua. We had a lot of small shallow drillholes. That was exploiting the geothermal system. That started to draw down the geothermal aquifer and stop the springs flowing, stop the geysers erupting.
Roku Mihinui
The concerns were expressed to the local district council who actually supported the fact that – or the assumption at the time – that the extraction of geothermal by residents and commercial users was affecting the geothermal activity. And they looked at banning – they put a 1.5 kilometre radius around the geothermal activity, and anybody within that area could not access the geothermal. There was a hell of a hue and cry about that, and a lot of the residents understandably were very upset, and there was a lot of political lobbying that happened, but in the end, the decision of the regional council where it sat was upheld, and all the extraction of geothermal within a 1.5 kilometre radius of Pōhutu was stopped.
Dr Ocean Mercier
The unique geothermal field that’s shaped the way the people of Whakarewarewa live has been severely compromised by overuse. With the haukāinga teaming up with scientists from GNS, they’re hopeful they can preserve the resource for generations to come.
The geothermal field that’s provided the people of Whakarewarewa with power and heat for centuries is under threat. Use by tourist operators and the growth of geothermal power as an energy source had combined to deplete the resource.
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.)
Kāore hoki he painga I te hau kāinga mō te mōhio ki ngā āhuatanga o ēnei waiariki I ngā wā o mua. (And no one knows more about how things were than the locals.)
Ngamohi Huata
I always tell my children this was the best time of my life was living in this village and in this house here. This is where I was brought up, there were 11 in the family, I’m the second to last – my sister and I the only ones born in a hospital – the rest born at home. Here, but this is our papa kāinga, it belongs to our whole family, not just one family. We had our own steam box, or our own microwave, so we had all of that so we didn’t have to move far to do anything at all.
Christina Gardiner
Because I grew up in the Urewera, but my paternal grandmother was from here. And Mick my husband was born and raised here. I was frightened at first, because I didn’t understand the geothermal. There were the old ladies, there were the younger mums around my age, and it was full with a lot of old people. And just down there was where we used to wash our clothes. Not everyone had a washing machine, we’d come down with sheets on our backs, and in our sheets were our clothes like Santa Claus, and our babies on the prams. And you’d have about four or five women sitting around and the babies in the warm water. And it was lovely, because while I was there, the older women of the village and the younger mums who were there with me, they’d be talking about life in the village. They actually helped us to settle in the village.
Roku Mihinui
We used to piggy back or sneak around behind our mothers and other guys and listen to their stories, and some of them were in their 80s, and they’re telling stories about when they were growing up here and what the geothermal activity was like back then. You know, that was used to be called to a great extent anecdotal evidence, but more and more now the scientific community is accepting that people’s interaction with the natural environment is actual information per se. And the term for that within Māori engagement is mātauranga, and it’s the living interactive knowledge that you gain with that particular taonga or gift or treasure and in this instance the geothermal.
Ngamohi Huata and Ringahora Huata
Te putanga iho, ko Te Hīrere, I whakawhiu ai ao Raho Peke
Ngamohi Huata
Poi, it actually – it retains all that history that has gone down, it retains on what is here now today, so we are able to point out to you the different locations. So that’s in song and dance all the time, that retains all the history of this whole area here, in terms of the hot pools, so in each hot pool, they all got a name and that something that happened in those times.
Ngamohi Huata and Ringahora Huata
Tukuna whakamua te poi e Hei a reia rau ka kite atu au Turi-Kore, i a Turi-kō-titi Nā rāua ko Roto-a-tama-heke Te putanga iho, ko Te Hīrere I whakawhiu ai ao Raho Peke
Ngamohi Huata
So I was sort of singing to her this morning, and she was singing back to me – Turi-Kore, Turi-kō-titi, Roto-a-tama-heke, Te Hīrere, Raho Peke – so that’s following that line of where we were this morning, yeah. So they can gauge this is the flow it’s taking, this is what happens, these are the names of these different lakes, this is the name of this area here where the babies are. Yeah, so that history is kept all the time. You can go even further back and then it goes on and on and on.
Dr Ocean Mercier
Kua whai hua ngā rangahau pūtaiao me ngā hotaka arotake a Brad I tēnei mātauranga. He kōrero tino hohonu tā te haukāinga me ngā kaipūtaiao mō te huatanga mai o ngā papa waiariki ki Rotorua. (This mātauranga has fed into Brad’s scientific enquiries and monitoring programme. The locals and scientists each have elaborate stories to explain the amazing geothermal field in the Rotorua region.)
Brad Scott
Here, we’re just standing beside Parekohoru, which is the hottest and largest discharging feature of the Whaka village. So this is one of the 40 pools or springs in Rotorua that we’ve chosen to monitor on a regular basis. And as this one discharges the most primary geothermal fluid coming from depth in the geothermal system, it’s by far the best indicator of the health of the system here in the village. And what we do here on a regular basis is we measure the temperature and the overflow from the pool and just see how that varies with time. In the geothermal system, one of the measures of the health is the height of the geothermal system – and if the pressures are high and the height is high, that will push fluid up and springs will overflow, and so therefore monitoring the overflow gives us a hint on if the system’s starting to decay, we’ll see a decrease in overflows.
So here we’re just going to take the temperature of the outflow using a digital thermometer and just watch the temperature rise – so we’re in the 80s, 90s – so we’re stabilised at 93.5° for the overflow here. That’s a very typical sort of temperature for this spring – it normally overflows in the low 90s. And the second measurement we’ll make here is the discharge – we’ve got a V-notch here, it’s a calibrated notch, and we’ll just measure the distance from the top of the notch down to the water level. For building up a history of the behaviour of the springs and knowing about the other things that are affecting it, like the number of drillholes that are open etc., we can just model the behaviour and health of the geothermal system, and we can use that as a management tool to decide how much geothermal fluid can be taken from the system, how much geothermal fluid should be put back into it. Are we taking too much or are we able to take some more?
Here in the village there are two large pools, Korotiotio and Parekohoru, both of which have been used to supply water to the oil baths – that’s where the people have their baths in the evening – so the overflow from these springs are captured and taken. And part of the indication that the Rotorua system was failing was when Korotiotio failed to overflow and there was no longer a discharge to feed the oil baths and were just using Parekohoru. And then ultimately in 1987, Parekohoru also failed. After the bore closure, Parekohoru started to overflow again and has a nice healthy overflow. Korotiotio, we’ve seen the water level rise, but we haven’t seen it rise back to overflow levels yet like it was back in the 60s.
Roku Mihinui
With the western science, the extraction of the geothermal and the non-reinjection would definitely affect the level of the aquifer or the water levels, which in turn would affect the geothermal activities. Now our people were also made aware of that, and because they have everyday interaction with the geothermal, they were used as monitors by various scientists. So on a day-to-day basis, two or three times a day, you were getting very exact scientific readings of the geothermal activity. So that became the interaction between the mātauranga and the western science that consolidated the information to allow scientists to be more confident in their predictions of factors affecting the geothermal activity.
Brad Scott
The monitoring regime that we have in place in Rotorua is actually to look at the health of the system and to measure whether or not the management plan is working. The whole idea of the management plan is to recover features, the surface features, enhance the behaviour of geysers and hot springs. So by monitoring the geothermal system – especially the surface expression – we are able to ascertain whether or not that monitoring plan is working. As you said, it’s a two-way process – we collect a lot of information about the geothermal system, and we also get a lot of feedback from the local people here and the guides, the changes in the springs when we’re not here, things like that. Our reporting on the status of the geothermal system is all fed back into the village, and this building that we’re actually utilising today and sharing here is part of our giving knowledge back to the village, and it’s an opportunity to share what Earth science and GNS is about.
Dr Ocean Mercier
Kia kaua ai e korehāhā tēnei taonga (Rather than lose the resource), a decision was made to scale back on its use – i te āhua nei e whai hua ana (and it seemed to be working). But the monitoring programme had yet to show any true indication of how successful the management plan for the geothermal resource had been.
Overuse had led to the Rotorua geothermal field losing power, and a management plan had been put in place to see if it could recover. Whakarewarewa locals were desperate to see that their resource – and their way of life – was maintained.
I whakarewahia he mahinga ngātahi ki a GNS kia pai ai te arotake I ngā hua o te aukati I ngā ngote waiariki. (A partnership with GNS to monitor the effects of closing off bores was under way to see if there had been improvements.) I tēnei rā, kei te arotake a Brad I te papa rēhia o Kuirau. (Today, Brad’s monitoring at Kuirau Park.)
Brad Scott
This pool here and the other features around us are actually part of the success story of the monitoring regime and the management plan for Rotorua. In the 1950s, 60s, these pools were like they are today. By the 1970s, 1980s, they’d dried up. People had been putting rubbish in them, there was discarded lawn mower chassis, pushbikes etc. And then in the early 90s, they started to fill up with water again following the bore closure programme. So once the bores were shut off, the geothermal system wasn’t being overexploited, and now they’re beautiful hot chloride geothermal features just as they were sort of 40 or 50 years ago. The geothermal features here at Kuirau Park in the northern part of Rotorua city are connected, they’re all part of the same geothermal system, and if what we see happening here transfers up to the south end of the system – to the Whaka system – then we’ll have a really good positive result.
Roku Mihinui
Actually, it took a few years before the aquifer or the water levels had risen significantly to then reinject activity into some of those mud pools and fumaroles and geysers that had suffered with the low levels. We’re lucky as well that we’ve had the opportunity to work closely with many of the scientific community.
Brad Scott
There’s always been an interest from a scientist’s perspective into understanding geothermal systems. They’re absolutely fascinating beautiful features, so scientists have always been around. In the early days, I guess it was fair to say that they didn’t share that knowledge as much as it’s done today. The main knowledge gained today from our work is that we can share it with the guides, and guides can then share it with the people that are visiting. And we can explain to the guides that these springs have different types of chemistry, they’ve evolved in different ways. Some are heated by steam, some are pure geothermal water, and they can actually pass that knowledge on to visitors, and it enhances the visitors’ experience when they come here.
John Waka
OK, well you’re getting a special treat today. It’s pigs head and potatoes. Now it’s been in there since 7 o’clock this morning. So we’ll just open it up, and as long as it doesn’t start squealing, we’ll know it’s cooked. I prefer this sort of cooking, especially for meats and that. It’s a natural thing. The minerals in the steam bring out the natural flavour of the food, so historically, we never put spices, we didn’t have spices. So all we had was plain food and salt – salt and pepper – but that was it, and so we know what the real food tastes like. And I still cook – even though I live just outside of the village and my family home is looked after by my sister – I still bring my food in here to cook because it’s something we’re used to, it’s something that’s special.
Now that’s the pigs head, we’ll leave that there now and we’ll bring the vegetables.
The food that we cook, we put into the hot pool to blanch – we blanch watercress then put it in the deep freeze, take it out when we’re ready and put it with the meat, and it’s totally different food.
That’s cabbage and kamokamo, and that’s been in there for about 15 minutes.
The minerals in the water bring out the natural flavour of the food.
Just cool that down a little bit. Right, here we have pork’s head, and we have the wild pork, and then we have the kamokamo and the potatoes, and in here we’ve got the cabbage. That’s all been cooked in the hot-water spring.
Brad Scott
It all fits into the sort of review of the Rotorua geothermal system, what the management plan objectives are. And it was really rewarding for us to actually see that we could recover hot springs, because it wasn’t really known when we shut the bores if the springs would recover. So it was a real positive for us to actually see the recovery and know that it can be done.
Roku Mihinui
Maybe cautiously confident that, in the next few years, we’ll have the hard evidence or data to say, “Yep, you can use this particular taonga, and this is how you need to use it to – for its own sustainability.” And that’s one of the critical things, you know, when I look behind me, and I see that the Blue Lake, there’s nothing, there’s just a little puddle. Where for myself and my children and my mother, that was one of our main swimming holes, because the water was warmer than the river anyway but cooler than the baths. So it was a good intermediary swimming area. There’s nothing there. Our baths down at the Hīrere only now are just at a level in the lakes where they’re starting to feed back, but albeit it takes a bit of time. We’ve had to dam parts of the lake to allow the water level to rise enough so that it can feed into the baths. So the, you know, the natural ability of the geothermal to look after itself is really sadly lacking and is going to need some scientific support to do that.
Dr Ocean Mercier
This relationship between Te Arawa and GNS Science has produced an outcome that’s exceeded expectation. The recovery of a system that had become severely depleted can be attributed to the closing of bores that were draining it of power.
Brad Scott’s monitoring programme indicates that the increase in activity seen in Kuirau will spread across the entire Rotorua geothermal field, ā, ko te ao e matapoporetia ana ki roto o Whakarewarewa, ka toitū tonu, whakatipuranga atu, whakatipuranga mai (and the way of life so treasured in Whakarewarewa can be maintained for generations to come).
Acknowledgements Video courtesy of Scottie Productions. © Scottie Productions 2013.
