Geological Model and Water Budget of the Hauraki Plains, Waikato Region, 2016
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Waikato Regional Council Technical Report 2018/04 Geological model and water budget of the Hauraki Plains, Waikato Region, 2016 www.waikatoregion.govt.nz ISSN 2230-4355 (Print) ISSN 2230-4363 (Online) Prepared by: PA White, C T Schritter, M Raiber (GNS Science Consultancy) For: Waikato Regional Council Private Bag 3038 Waikato Mail Centre HAMILTON 3240 Doc Creation Date: May 2018 Doc # 6377264 Peer reviewed by: Beban Jenkins Sung Soo Koh Date May 2018 Approved for release by: Date May 2018 Liz Tupuhi Disclaimer This technical report has been prepared for the use of Waikato Regional Council as a reference document and as such does not constitute Council’s policy. Council requests that if excerpts or inferences are drawn from this document for further use by individuals or organisations, due care should be taken to ensure that the appropriate context has been preserved, and is accurately reflected and referenced in any subsequent spoken or written communication. While Waikato Regional Council has exercised all reasonable skill and care in controlling the contents of this report, Council accepts no liability in contract, tort or otherwise, for any loss, damage, injury or expense (whether direct, indirect or consequential) arising out of the provision of this information or its use by you or any other party. Geological model and water budget of the Hauraki Plains, Waikato region PA White M Raiber C Tschritter GNS Science Consultancy Report 2015/232 May 2018 DISCLAIMER This report has been prepared by the Institute of Geological and Nuclear Sciences Limited (GNS Science) exclusively for and under contract to Waikato Regional Council. Unless otherwise agreed in writing by GNS Science, GNS Science accepts no responsibility for any use of or reliance on any contents of this report by any person other than Waikato Regional Council and shall not be liable to any person other than Waikato Regional Council, on any ground, for any loss, damage or expense arising from such use or reliance. Use of Data: Date that GNS Science can use associated data: May 2018 BIBLIOGRAPHIC REFERENCE White PA, Raiber M, Tschritter C. 2018. Geological model and water budget of the Hauraki Plains, Waikato region. Wairakei (NZ): GNS Science. 63 p. (GNS Science consultancy report; 2015/232). Project Number 631W0519 Confidential 2015 CONTENTS EXECUTIVE SUMMARY ....................................................................................................... V 1.0 INTRODUCTION ........................................................................................................1 2.0 REVIEW OF THE GEOLOGY AND HYDROGEOLOGY OF THE HAURAKI PLAINS....................................................................................................................... 3 2.1 Geological Structure ...................................................................................................... 6 2.2 Major Geological Units ................................................................................................ 11 2.2.1 Basement Greywacke .................................................................................... 11 2.2.2 Tertiary Sediments and Volcanics .................................................................. 11 2.2.3 Quaternary Sediments ................................................................................... 11 2.2.3.1 Pleistocene pre-Hinuera Formation ................................................ 12 2.2.3.2 Pleistocene Hinuera Formation....................................................... 12 2.2.3.3 Holocene Alluvial Deposits ............................................................. 17 2.2.3.4 Holocene Piako Swamp and Kopuatai Peat Dome ........................ 17 2.2.4 Quaternary Volcanics ..................................................................................... 17 2.2.4.1 Waiteariki Ignimbrite ....................................................................... 17 2.2.4.2 Pakaumanu Group .......................................................................... 17 2.2.4.3 Mamaku Plateau Formation ............................................................ 17 2.2.5 Some Published Lithological Observations from Drill Holes .......................... 18 2.3 Geothermal Features and Hot Springs........................................................................ 20 3.0 METHODOLOGY ..................................................................................................... 22 3.1 3D Geological Model ................................................................................................... 22 3.1.1 Introduction ..................................................................................................... 22 3.1.2 Model Data Sources ....................................................................................... 23 3.1.2.1 Topographic Data ........................................................................... 23 3.1.2.2 Geological Maps ............................................................................. 23 3.1.2.3 Cross Sections ................................................................................ 23 3.1.2.4 Well Log Data.................................................................................. 23 3.1.2.5 Loss of Lithological Information in the WRC Lithology Database ... 23 3.1.3 Grouping of Formations into Model Units ....................................................... 24 3.1.4 Model Units Description ................................................................................. 28 3.1.4.1 Basement ........................................................................................ 28 3.1.4.2 Tertiary Waiteariki Ignimbrite .......................................................... 28 3.1.4.3 Pleistocene Pakaumanu Group Ignimbrite ..................................... 28 3.1.4.4 Early Quaternary Tauranga Group Sediments ............................... 28 3.1.4.5 Pleistocene Mamaku Plateau Formation Ignimbrite ....................... 29 3.1.4.6 Greywacke Gravel from Hapuakohe Range ................................... 29 3.1.4.7 Pleistocene Hinuera Formation....................................................... 29 3.1.4.8 Holocene Coastal Sediments.......................................................... 29 3.2 Water Budgets ............................................................................................................. 30 3.3 Model Data .................................................................................................................. 31 3.4 Water Budget Calculation ............................................................................................ 33 GNS Science Consultancy Report 2015/232 i Confidential 2015 4.0 RESULTS ................................................................................................................. 39 4.1 Digital Terrain Model and the Southern Limits of the Holocene Marine Incursion ...... 39 4.2 Hauraki 3D Geological Model ...................................................................................... 39 4.3 Water Budgets ............................................................................................................. 46 5.0 DISCUSSION............................................................................................................ 54 5.1 Water Budget Components ......................................................................................... 54 5.2 Long-term Average Flow Estimates ............................................................................ 54 5.3 Sub-catchment Boundaries ......................................................................................... 55 5.4 Uncertainties in Water Budget Components ............................................................... 55 5.5 Potential for Groundwater Flow Between the Major Catchments ............................... 56 5.6 Piako River Catchment: Comparison of Water Budgets ............................................. 56 6.0 RECOMMENDATIONS ............................................................................................. 57 6.1 Well Logs ..................................................................................................................... 57 6.2 Geological Model ......................................................................................................... 57 6.3 Water Budget Components and Zone Boundaries ..................................................... 57 6.4 Long-term Flow Estimates ........................................................................................... 57 6.5 Uncertainty .................................................................................................................. 57 7.0 CONCLUSIONS ....................................................................................................... 58 8.0 ACKNOWLEDGEMENTS ......................................................................................... 59 9.0 REFERENCES ......................................................................................................... 60 ii GNS Science Consultancy Report 2015/232 Confidential 2015 FIGURES Figure 1.1 Location of the Hauraki Pains area with the boundary of the Hauraki geological model developed in this report. ............................................................................................................... 2 Figure 2.1 Summary geological map of the study area, after Leonard et al. (2010) and Edbrooke (2001).... 4 Figure 2.2 Location of Hauraki and