| Title | Using temperature methods to improve geyser monitoring at Rotorua, New Zealand |
|---|---|
| Authors | B. Keats, R. Reeves, B. Scott, M. Zuquim, P. Doorman, J. Shanks, N. Macdonald, L. Coup |
| Year | 2023 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | geyser, temperature, surface features, geothermal monitoring |
| Abstract | Geothermal surface features in the Rotorua Geothermal System (RGS) hold significant cultural, economic, and environmental value to Bay of Plenty Regional Council (BOPRC) and local iwi groups. Activity at many of these surface features have been recovering since the bore closure program was instigated in 1986. The recovery has been variable however, and appropriate data to monitor these long-term trends has not always been available. BOPRC therefore partnered with Te Puia, New Zealand Maori Arts and Crafts Institute, and GNS Science to trial a temperature sensor based monitoring system at Geyser Flat, Te Puia in late 2022. Five thermocouple temperature sensors were deployed around Pohutu and Te Tohu (Prince of Wales Feathers) Geysers, and one at the outlet of Te Horu overflow pool from October 2022 to July 2023. Observational datasets of eruptive activity at the site were also acquired and used to help develop an algorithm to translate the recorded temperature data into a record of eruptive activity. A clear pattern was immediately evident in the data. Eruptive activity typically began at the Te Tohu Geyser vent, with eruptions at Pohutu following around 15-20 minutes later. Both geysers then continued erupting together for another 30-60 minutes, before ceasing activity simultaneously. This pattern is consistent with historic observations (e.g. Lloyd, 1975) where activity at Te Tohu precedes Pohutu. While the data could be noisy, the algorithm appeared to work well throughout the trial period, with the flagged start and end of eruptions typically within 6 and 3 minutes of the observed eruption start and end, respectively. Recorded eruptive activity is very consistent, with 17 eruptions occurring each day on average, and more than 50% of each day spent in an eruptive state. Eruptions lasted an average of 37 and 54 minutes at Pohutu and Te Tohu respectively, notably higher than any previously reported values. |