GNS Science Report 2013/46
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BIBLIOGRAPHIC REFERENCE Rose, J., Zemansky, G. 2013. Potential effects of volcanic activity on level and quality of associated groundwater, GNS Science Report 2013/46. 22 p. J. Rose, GNS Science, Private Bag 2000, Taupo 3352 (current address: 4544 County Road 25 SW, Hoffman, Minnesota, USA 56339). G. Zemansky, GNS Science, Private Bag 2000, Taupo 3352 (current address: Prime Hydrogeology Ltd., 119 Lakewood Drive, Taupo) © Institute of Geological and Nuclear Sciences Limited, 2013 ISSN 1177-2425 ISBN 978-1-972192-93-1 CONTENTS ABSTRACT ...........................................................................................................................II KEYWORDS .......................................................................................................................... II 1.0 INTRODUCTION ........................................................................................................ 1 2.0 LITERATURE REVIEW .............................................................................................. 2 2.1 Groundwater Level Monitoring Around Volcanoes ........................................................ 2 2.2 Groundwater Chemistry Monitoring Around Volcanoes ................................................ 3 3.0 EXISTING MONITORING DATASETS WITHIN NEW ZEALAND ............................... 6 3.1 Ruapehu ........................................................................................................................ 6 3.1.1 Well Information................................................................................................. 6 3.1.2 Water Quality Data ............................................................................................ 8 3.2 Tongariro ....................................................................................................................... 9 3.2.1 Well Information................................................................................................. 9 3.2.2 Water Quality Data .......................................................................................... 10 3.3 Taranaki ....................................................................................................................... 10 3.3.1 Well Information............................................................................................... 10 3.3.2 Water Quality Data .......................................................................................... 11 3.4 White Island ................................................................................................................. 12 3.4.1 Well Information............................................................................................... 12 3.4.2 Water Quality Data .......................................................................................... 12 3.5 Raoul Island ................................................................................................................. 13 3.5.1 Well Information............................................................................................... 13 3.5.2 Water Quality Data .......................................................................................... 13 4.0 SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS .................................... 14 5.0 REFERENCES CITED .............................................................................................. 15 FIGURES Figure 1: Locations of sampling sites, wells, and springs near Ruapehu and Tongariro. ............................ 7 Figure 2: Silica Rapids chemistry plots. Solid bar lines represent eruptions from Ruapehu. ...................... 9 Figure 3: Locations of wells, springs, and a seepage near Taranaki. ........................................................ 11 Figure 4: Water sampling and record locations at White Island. ................................................................ 12 APPENDICES APPENDIX 1: GGW WATER QUALITY DATA ELECTRONIC FILES (ENCLOSED ON CD)18 ENCLOSURES CD Containing: A. Chemdata Formatted for NGMP Calc.xls; B. Detailed Chem Data.xlsx; C. GNS GGW Existing Chem Datasets.xls; D. NGMP Stats Calculator Output File.xlsx; E. Silica Rapids Chem Data.xls; F. Soda Springs Chem Data.xlx GNS Science Report 2013/46 i ABSTRACT Groundwater level and quality changes preceding eruptive volcanic activity could potentially have predictive value if closely monitored. Groundwater levels have been reported in the scientific literature to change (both rise and fall) in conjunction with volcanic activity in Japan and in the Philippines. There are also reports of changes in the quality of groundwater in wells, springs, and crater lakes in a number of other places in the world in association with volcanic activity as well as New Zealand. However, there is some inconsistency in the data with changes sometimes being documented while at other times either being in the opposite direction or not seen at 2+ 2+ + all. These include increases in B, Ca , Mg , Na , and SiO2 of springs in advance of 2- eruptive activity at Popocatepetl volcano in Mexico, an increase in SO4 concentrations for a thermal spring on the flank of Tacana volcano in Mexico prior to an eruption as well as variations in B, total Fe, and Mg2+. In New Zealand, these include increases prior to the 1995 2+ 2+ eruption in levels of Al, Ca , Fe, Mg , Na, SO4, Cl, and conductivity, decreases in SO4 and Cl prior to the September 2007 eruption, and increases in spring-fed Silica Rapids 2+ 2+ + - - 2- concentrations of Ca , Mg , Na , HCO3 , Cl , SO4 , and conductivity and decreases in Al, Fe, and temperature in association with the 1995 and 1996 Ruapehu eruptions and a decrease Al in association with the September 2007 Ruapehu eruption. The GNS Science GGW database contains a number of locations in proximity to volcanoes. These data and a statistical analysis output sheet are provided in an Appendix to this report. Both of the authors of this report have left employment at GNS Science before they could comprehensively evaluate these data. We recommend that such an evaluation occur as the next step in this programme. We also recommend that an effort be made to develop a number of real groundwater monitoring sites, including wells and springs, in relatively close proximity to the most active volcanoes in New Zealand. Mt. Ruapehu, Mt. Tongariro, and White Island are candidates for such monitoring. Monitoring should include continuous water level and conductivity measurements and frequent sampling for major ions and other selected water quality variables (e.g., Al, B, Fe, and SiO2). Continuous water level and conductivity measurements could be telemetered for real-time monitoring to the Wairakei Research Centre. Annual sampling to analyse for major ions and other selected water quality variables is insufficient for the purpose. Quarterly or possibly monthly with an increase in frequency if changes are detected that warrant it are recommended. This list could be fleshed out with reference to known indicators of geothermal geochemistry in New Zealand. There is a rich literature in that regard. KEYWORDS Groundwater, volcanoes, water levels, water quality GNS Science Report 2013/46 ii 1.0 INTRODUCTION In the latest international review of the volcanology programme of the Institute of Geological and Nuclear Sciences (GNS Science), it was recommended that the relationship between volcanic activity and groundwater and the potential for groundwater monitoring as an indicator of volcanic activity be assessed. Groundwater level and quality monitoring have been used internationally to monitor volcanic activity elsewhere for some time, but this has not been done in a formalized way in New Zealand. This report documents a literature review of what groundwater level and water quality changes have been attributed to volcanic activity internationally and describes the existing monitoring datasets that are available within New Zealand related to groundwater. Recommendations for a groundwater monitoring program within New Zealand are then presented. GNS Science Report 2013/46 1 2.0 LITERATURE REVIEW 2.1 GROUNDWATER LEVEL MONITORING AROUND VOLCANOES “Rising magma and groundwater invariably interact” (Newhall et al., 2001). Groundwater level changes prior to volcanic eruptions have been studied, but few observations have been recorded over time. Newhall et al. (2001) cited examples of water level changes before eruptions observed at numerous volcanoes dating from the 1500’s to the present. Sparks (2003) noted that groundwater emissions and changes in water tables prior to eruptions are likely caused by rising magma opening up fracture systems and disturbing groundwater systems. Groundwater level and spring discharge changes may occur when pore water pressure is raised by heating from rising magma or raised/lowered by mechanical strain in confined aquifers (Newhall et al., 2001). Groundwater level changes prior to volcanic activity have been observed at Mayon Volcano, Philippines and Miyake-jima, Usu, and Meakan-dake volcanoes, Japan as follows: • Mayon Volcano, Philippines - Residents approximately 8 to 15 km away from the summit of Mayon observed groundwater levels drop (up to 5 m) in wells in a shallow unconfined aquifer prior to the 1993 eruption (Newhall et al., 2001; Albano et al., 2001; and Jentzsch et al., 2001). Modeling of the groundwater system using MODFLOW by Albano et al. (2002) indicated that the water level changes were likely caused by enhanced permeability (opening of fractures) and rainfall pattern changes.