Rotorua's once-famous Waikite Geyser is showing signs of rejuvenation after 43 years of very little activity, scientists say.
Waikite was once the ‘crown jewel’ of geysers at Whakarewarewa geothermal area, but it has not produced a significant steam eruption since 1969.
In the first half of last century Waikite was known for its spectacular displays, with hot water eruptions reaching 20m in height. It had occasional quiet periods, sometimes lasting more than a year, but never as long as 40 years.
Scientists believe a sharp increase in the number of bores in Rotorua since the 1950s contributed to the decline of many geysers, including Waikite. The widespread withdrawal of hot fluid caused underground pressures to drop.
In the 1980s scientists advocated closing down many bores as they were detracting from Rotorua’s natural thermal attractions. In spite of strong resistance from some bore owners, about 300 bores were eventually closed within a 1.5km radius of Whakarewarewa.
For a number of years GNS Science has maintained a monitoring programme of the geysers and geothermal features in Rotorua. In the past year, scientists have increasingly noticed geothermal waters coming into the throat of Waikite Geyser.
Geothermal features were naturally variable, and could be dormant for some years, said Geothermal Scientist Ed Mroczek, of GNS Science.
“This makes it difficult to distinguish what is part of a natural cycle and what is disruption caused by human activity,” Dr Mroczek said.
“Our monitoring has shown that not all geysers and springs have returned to their former state, but it is really encouraging to see signs of activity at Waikite.”
Dr Mroczek said elevated levels of chloride in the hot water at Whakarewarewa indicated that pressure had increased and water from deeper in the earth was being pushed toward the surface.
“We have no way of knowing if Waikite will recover to its former magnificence, but the signs we are seeing are very encouraging."
Dr Mroczek and colleagues believed that the most important lesson from the decline of the Whakarewarewa geyser field was the fragile nature of New Zealand’s geysers.
Historically New Zealand had the highest number of documented geysers in the world apart from Yellowstone Park in the United States. But that number had dwindled over the past 50 years to just a handful.
Managing the opposing pressures of use and conservation was a challenge, but there were signs that a healthy balance had been reached in Rotorua.
“With careful management and appropriate technologies, you can have both use and protection of the features for the economic benefit of Rotorua and New Zealand.
Geothermal specialist at GNS Science, Duncan Graham, said he was encouraged by the return of geothermal surface features since the bore closers in the 1980s.
“I guess we are lucky because we can see the features first-hand. We are all very passionate about the geothermal features,” Mr Graham said.
“When you arrive at one of Rotorua’s geothermal areas, locals want to talk about the features like they are talking about their family. They might say ‘Oh Karotiotio is getting a bit grumpy, or something like that. It’s part of the character of Rotorua.”