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Time series analysis of selected geothermal spring temperature recordings

TR 2013/17
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Report: TR 2013/17

Author: P Nikrou (Massey University), J Newson (University of Auckland) and R McKibbin (Massey University)

Abstract

The subject of this study is data collected from the Waiotapu Geyser at the Waiotapu Thermal Area, and the Soda Fountain Pool at Orakei Korako.

Most temperature monitoring is 'spot' or a single measurement per visit, which results in data points three months to one year apart. However the data presented here is temperature time series data from two boiling or near-boiling springs. Each time series is 45 days long, and the time between data collection points is two minutes.

The two springs which are the subject of this study exhibit cyclic temperature variation.

The first high-temperature spring, the Waiotapu Geyser, has a mean temperature over the recording time of 86.76°C, and shows times of strong cyclic activity that continues for two to six days, with intervening times of non-cyclic behaviour. Data from this spring has a distinctive 'shape' of the temperature cycle which appears to be independent of frequency.

The second, the Soda Fountain at Orakei Korako, exhibits cyclic temperature variation over the entire data collection interval. The pools also exhibit water-level changes, although unfortunately these were not recorded due to equipment limitations.

This study here is a qualitative and quantitative analysis of the data from the two springs described above. Avenues of investigation were:

  • a relation between climate data (rainfall, air pressure, and air temperature) and spring temperature
  • a relation between seismic events and spring temperature
  • whether there are dominant frequencies in the cyclic data
  • a detailed examination of the relationship between spring activity and air pressure.

The report concludes with a discussion of the lessons from this study and recommendations for future monitoring programmes.

Time series analysis of selected geothermal spring temperature recordings [PDF, 4.8 MB]