The hydrogeology of the Pourewa sub-catchment, Rangitikei, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Science at Massey University, Palmerston North, New Zealand

Thumbnail Image
Open Access Location
Journal Title
Journal ISSN
Volume Title
Massey University
The Author
This story begins in the geologically young and active landscapes of the lower North Island of New Zealand, positioned astride the interface between the Pacific and Australian tectonic plates. The chosen field area is located within the onland Whanganui Basin, a Late Miocene-Quaternary marine basin that has undergone uplift, inversion and fluvial incision to form spectacular river valley exposures through the basin succession. The area contains one of the most complete records of Quaternary climate change exposed onland anywhere in the world. Our journey centres on a portion of this uplifted marine basin, characterised by the highly erodible, pastorally farmed hill country of the Rangitikei. The Pourewa Stream, a tributary of the Rangitikei River provides a cross section through rural landscapes of the lower North Island. The stream’s headwaters begin in steep Taihape sheep and beef country, before transitioning into a broad valley with a gentle gradient headed for Hunterville. The lower reaches step down across extensive Late Pleistocene river terraces, providing versatile arable cropping and dairy pasture, until finally joining the Rangitikei River 6 km east of Marton. Agriculture constitutes 90% of land use in the region, placing pressure on resources required for ongoing agricultural development and production. Recent concerns surrounding the long-term sustainability and potential contamination of freshwater resources have initiated research into the regions groundwater system. Previous studies have taken a broad approach examining large-scale issues surrounding classification, allocation, management and vulnerability of groundwater resources. This study takes a different approach by examining a single sub-catchment of the Rangitikei River, with the aim of developing a conceptual hydrogeological model for the Pourewa Stream area. The proposed model is underlain by a comprehensive stratigraphic investigation of the Quaternary succession in the central Rangitikei. Geological context is provided through the development of a 1:25 000 geological map series and accompanying structural interpretation. Hydrogeochemical datasets derived from targeted in situ and laboratory based analysis provide baseline information. The conceptual hydrogeological model is applied on a wider regional scale to investigate basin history and processes of landscape formation. The project aims to support policy makers, landowners and developers in achieving sustainable management of groundwater resources by the avoidance of over exploitation and contamination.
Listed in 2020 Dean's List of Exceptional Theses
Figures are licensed as follows: Land Information New Zealand (LINZ) under the Creative Commons Attribution 4.0 International License; Ministry for the Environment (MFE) under the Creative Commons Attribution 3.0 New Zealand License; National Institute of Water and Atmospheric Research (NIWA) under the NIWA Open Data License v 1.0.
Hydrogeology, Hydrogeological modeling, New Zealand, Rangitikei District, Dean's List of Exceptional Theses