New Zealand’s energy security depends on gas, but our only local source is sitting on top of an active volcano.
New data shows an eruption at Mount Taranaki could eliminate two-thirds of the regional economy, leave New Plymouth without power and threaten major industry nationwide – with eruptions occurring more frequently and with less warning than we thought.
The findings come from five years of research under the Transitioning Taranaki to a Volcanic Future programme and were released today. The project’s leaders gave Newsroom an exclusive preview, in which they outlined how targeted investments in the near future could save over a billion dollars of damage while keeping communities out of harm’s way.
Gas is a critical piece of New Zealand’s energy budget, representing energy security and the lifeblood of many heavy industries still reliant on fossil fuels.
In times of crisis, New Zealand has leaned on local gas production to ease pressure on hydro lakes. But the gas fields from which this fuel is sourced are found around Mt Taranaki, an active volcano with the potential to disrupt the gas system in an eruption.
‘It is quite conceivable that a number of wells that are currently producing would not be able to be restarted without some very substantial investment‘
Civil engineer Roger Fairclough
If Taranaki were to erupt and damage nearby operations, New Zealand’s usual source of energy security could be taken offline for months, and industries would be unable to operate without imported fuel. The maunga has a 30 to 50 percent chance of eruption in the next 50 years.
But investments in infrastructure and planning could save up to a billion dollars in damages, according to a new study co-created by Tom Wilson, a volcanologist at the University of Canterbury, and Roger Fairclough, a civil engineer and owner of consulting firm Neo Leaf Global.
The study was funded by the Ministry of Business, Innovation and Employment via the Endeavour Grant, one of several contestable science funding streams set to be merged into a centralised funding body as part of wider sector reforms.
What came from the research was a situation Fairclough described as “quite unique” from a global energy security perspective: no other country has a single gas field to draw on which also happens to sit atop an active volcano.
To assess what level of threat this situation posed, their research programme developed the most realistic eruption scenarios for a New Zealand volcano to date, with nine possible outcomes. Small, medium and large eruptions were modelled, with each category broken down into another three-tier division.
Fairclough said the value of the modelling was its ability to look into the future, years beyond the initial eruption, to offer a better picture of how such an event would affect New Zealand’s economy and energy supply.
“Most people assume a volcano erupts, you’ve got a massive explosion, massive lahars [volcanic mudslides], all that sort of thing, and then over a period of time that dissipates,” he said. But Fairclough expected a sequence of intermittent activity rather than a single, dramatic event.
“One of the things we were testing with the oil and gas field operators was ‘How long does it take you to restart if you do shut down? Is it five days? Is it 30 days?’ And no one really knows, and none of us will know until it actually happens,” said Fairclough.
These fields could need to be reset for two reasons: either they were damaged during the event and needed to be repaired, or they were shut down in anticipation of the event and need to come back online. Either way, staff would need to access the infrastructure, which might not be possible depending on evacuations and damages.
Even if staff could access the site, there was another problem: if gas ever stops flowing from its underground reservoir, it could be very difficult to get it going again. Without pumping, water enters the reservoir, making work to restart extraction more expensive than it’s worth.
“It is quite conceivable that a number of wells that are currently producing would not be able to be restarted without some very substantial investment,” said Fairclough.
‘We know we want a thriving economy, but a thriving economy needs to be a resilient one, where it’s not constantly disrupted by extreme shocks and buffeted constantly‘
Volcanologist Tom Wilson
According to Fairclough, rising gas prices meant many industries were already thinking about transitioning to alternative fuels, but this would take time.
Wilson said this could be seen as an opportunity. The severe damage predicted by some of the high-end scenarios made Wilson think “there’s a question there of do you commit to rebuilding and commit to reinstating that infrastructure and therefore that supply? Or is this the sort of disruption event or disaster event that leads to a much more rapid transition to something else?”
New Plymouth risks being cut off from the grid
New Zealand’s gas fields are dotted around Taranaki maunga. In the north and west are the Maui and Pohokura fields; to the south are Kapuni and Kupe. Transmission pipelines connect the north and south operations.
Directly to the east of Taranaki is the small town of Stratford, which hosts an exit point for the wider electricity grid. From here, energy leaves the national grid and heads towards New Plymouth and the surrounding towns. It is the only external supply of energy to this part of the country.
One of the most likely impacts of an eruption would be to this critical node in Stratford. A lahar, a mudslide triggered by volcanic activity, could hurtle down the mountain and damage it, cutting off the New Plymouth area from the rest of the country.
Fairclough said in this scenario the strategy would be to enable it to be “islanded”: capable of generating its own power, separate from the national grid. With gas fields nearby and a growing solar capacity, this was possible – but not yet. The spread and location of facilities and staff meant an islanded New Plymouth wasn’t a guarantee.
Another likely impact was that the gas transmission line from south to north Taranaki could be broken, cutting the gas system in half.
Fairclough said one of the tests his team posed to the energy companies was the ability to operate the south and north energy systems independently. “For various reasons, we’re not able to, at present. These reasons include the location of the control systems, access to staff and access to the plant and all those sorts of things.”
Less warning time than we thought
“As you can imagine, one of the big challenges in volcanology is forecasting eruptions,” said Wilson.
Volcanic eruptions are preceded by rumblings, but it can be difficult to determine what was a warning and what was normal behaviour without the gift of hindsight. This meant developing a detailed picture of Taranaki’s internal geology was key to understanding its future behaviour.
Wilson’s team found the first evidence of magma below the volcano’s surface, sitting 4-12km below the ground. This was far shallower than expected, and the magma below Taranaki was rising to the surface faster than almost anywhere else in the world.
Together, this meant the time between initial unrest and eventual eruption would be shorter than assumed, with more frequent eruptions. New Zealand’s window of warning could be just a few weeks, if the warning signs were recognised.
Beyond impacts to the nearby energy sector – which Wilson said could be quite severe – the lasting impact of the eruption would be felt by the region and the nation for years.
Spend now, save later
“One of the big transformative steps forward was to couple the economic modelling with the volcano risk modelling,” said Wilson.
Understanding the second- and third-order disruptions from an eruption – for example children being able to attend school, and on-farm water supplies and energy supply – were what allowed Wilson’s team to compare their modelled results with disasters in New Zealand’s past or future.
“It allows us to start to compare apples with apples – what does this look like compared to an Alpine Fault earthquake or an Auckland volcanic field eruption or the Covid-19 pandemic?” asked Wilson.
“It allows us to start looking at what’s the benefit – or otherwise – of different mitigation and where the best bang for buck might be, in terms of the very precious resilience dollars that we have,” said Wilson.
“What does it mean to not have electricity for six months or three months? What does it mean if your water’s out? You know, particularly in south Taranaki, where they’re very reliant on most of the farms being supplied by stream-fed water supplies that come off the maunga, there’s not a lot of storage on-farm. So within a day, those farms are out of water – that could be really challenging, particularly during a dry summer.”
Water and energy security were the two main areas Wilson’s team saw an opportunity to invest.
Creating an islanded New Plymouth system and investing in borehole water supplies in South Taranaki could save an estimated $1.1 billion.
In practical numbers, this translated to 17,000 fewer homes without power and 8,000 fewer without water.
Wilson said: “In some ways, the impetus now is for critical infrastructure companies, maybe regional economic development agencies and even government ministries, to pick this up.
“We know we want a thriving economy, but a thriving economy needs to be a resilient one, where it’s not constantly disrupted by extreme shocks and buffeted constantly.”
Energy Minister Simon Watts and Regional Development Minister Shane Jones were approached for comment, but did not respond in time for publication.