Geological model and water budget of the Hauraki Plains, Waikato Region, 2016

TR 2018/04
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Report: TR 2018/04

Author: PA White, CT Schritter, M Raiber (GNS Science Consultancy)

About this report

This report summarises the geological information of the Hauraki plain aquifer available to date in the form of 3D model, maps and geological descriptions. It reviews existing publications, borelogs, cross-section information and expert understanding of the aquifer. Water budget was included for the Piako and the Waihou river catchments to illuminate the interaction between GW and SW systems.

These information were summarised and published so that they may be referenced in future groundwater investigations in the area. The nature of the publication is highly technical and it has limited direct implications in resource management regulation and practice. However, the information is valuable in other science and technical works foreseen in the future.

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Geological model and water budget of the Hauraki Plains, Waikato Region, 2016 [PDF, 3.2 MB]

Contents
  Executive summary
1 Introduction
2 Review of the geology and hydrogeology of the Hauraki Plains
2.1 Geological structure
2.2 Major geological units
2.2.1 Basement greywacke
2.2.2 Tertiary sediments and volcanics
2.2.3 Quarternary sediments
2.2.3.1 Pleistocene pre-Hinuera formation
2.2.3.2 Pleistocene Hinuera formation
2.2.3.3 Holocene alluvial deposits
2.2.3.4 Holocene Piako Swamp and Kopuatai Peat Dome
2.2.4 Quaternary volcanics
2.2.4.1 Waiteariki ignimbrite
2.2.4.2 Pakaumanu Group
2.2.4.3 Mamaku Plateau formation
2.2.5 Some published lithological observations from drill holes
2.3 Geothermal features and hot springs
3 Methodology
3.1 3D geological model
3.1.1 Introduction
3.1.2 Model data sources
3.1.2.1 Topographic data
3.1.2.2 Geological maps
3.1.2.3 Cross sections
3.1.2.4 Well log data
3.1.2.5 Loss of lithological information in the WRC Lithology Database
3.1.3 Grouping of formations into model units
3.1.4 Model units description
3.1.4.1 Basement
3.1.4.2 Tertiary Waiteariki ignimbrite
3.1.4.3 Pleistocene Pakaumanu Group ignimbrite
3.1.4.4 Early Quaternary Tauranga Group sediments
3.1.4.5 Pleistocene Mamaku Plateau formation ignimbrite
3.1.4.6 Greywacke gravel from Hapuakohe Range
3.1.4.7 Pleistocene Hinuera formation
3.1.4.8 Holocene coastal sediments
3.2 Water budgets
3.3 Model data
3.4 Water budget calculation
4 Results
4.1 Digital terrain model and the southern limits of the Holocene marine incursion
4.2 Hauraki 3D geological model
4.3 Water budgets
5 Discussion
5.1 Water budget components
5.2 Long-term average flow estimates
5.3 Sub-catchment boundaries
5.4 Uncertainties in water budget components
5.5 Potential for groundwater flow between the major catchments
5.6 Piako River catchment: comparison of water budgets
6 Recommendations
6.1 Well logs
6.2 Geological model
6.3 Water budget components and zone boundaries
6.4 Long-term flow estimates
6.5 Uncertainty
7 Conclusions
8 Acknowledgements
9 References