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2010 interpretation of geochemical data (REGEMP II) and recommendations for further monitoring

On this page: Abstract, table of contents

Report: TR 2012/07

Author: JG Webster-Brown & KL Brown (GEOKEM)


This report updates a previous assessment made of monitoring data collected from geothermal features in the Waikato region (Webster-Brown and Brown, 2008). The objectives of this monitoring programme are:

  • to understand the nature and vulnerability of the region’s warm water resources to change, in order to sustainably manage these resources
  • to determine likely changes in the environmental impacts of these features/systems.

The 2008 assessment had been based on monitoring data collected in 2005/06, as well as previous data reported in Huser & Jenkinson (1996), and data for features in Tongariro National Park and Tokaanu made available from the GEONET program administered by GNS Science.

In this report, the assessment has now been updated to include:

  • 2009 monitoring data for the fluids of 39 geothermal features, analysed for parameters of geothermal relevance
  • spatial and temporal trends in the monitoring data to date
  • interpretation of historic gas data for selected fumaroles and geothermal wells
  • a comment on arsenic speciation research undertaken at the University of Surrey, and whether speciation analysis should be incorporated into the monitoring programme
  • recommendations for future monitoring and for incorporation of historic fluid geochemistry data into the monitoring dataset.

2010 interpretation of geochemical data (REGEMP II) and recommendations for further monitoring

Table of contents

  Executive summary 4
1 Introduction 6
1.1 Technical brief 6
1.2 2009 fluid geochemical monitoring data 7
1.3 Historic data for fluid geochemistry 7
1.4 Historic data for gas geochemistry 7
1.5 Changes relative to the REGEMP II report format 8
2 Data compilation and assumptions 8
3 Fluid geochemistry data correlations 9
3.1 Correlations in updated dataset 10
4 Spatial trends in fluids geochemistry 13
4.1 One dimensional analysis: North to south 13
4.2 Variation in fluid geochemistry across the region 19
5 Temporal trends 21
5.1 Individual features 21
6 Arsenic speciation study 40
7 Gas geochemistry data 40
8 Recommendations 42
8.1 Data collected from each site 42
8.2 Recommendations for sites sampled 42
8.3 Recommendations for historic data incorporation 43
9 References 44
  Appendix I - List of fluid geochemical data used in report 45
  Appendix II - Sites monitored in the 2009 programme 19
  Appendix III - List of gas data used in report 19