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Subject: search.filters.subject.370703 Groundwater hydrology

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    Geothermal exploration using hyperspectral and thermal remote sensing : inferring shallow hydrology of the Waiotapu Geothermal Field, New Zealand : a thesis presented in partial fulfilment of the requirements of the degree of Doctor of Philosophy in Earth Sciences at Massey University, (Manawatū Campus), Palmerston North, New Zealand
    (Massey University, 2023) Rodriguez-Gomez, Cecilia
    Geothermal areas can exhibit a series of surface manifestations (e.g. mineral alteration and deposition, thermal anomalies, hot springs, and characteristic plant species) which can be directly detected with remote sensing techniques within the visible, near-infrared, and thermal ranges. These surface manifestations are, to some extent, a reflection of the subsurface activity. There is a wealth of techniques, including geological, geophysical, and geochemical methods, which can be used to explore and monitor geothermal areas; however, remote sensing techniques from airborne and spaceborne platforms can provide a cost-effective alternative. In many cases, geothermal areas are densely covered by vegetation which can further increase the time and cost of exploration. However, vegetation has the capability to reflect the environment it lives in. Here, we propose vegetation can be utilised as a proxy for subsurface geothermal activity using a combination of hyperspectral (VNIR/SWIR), thermal infrared, and LiDAR imagery with rock/soil and plant elemental concentration values. These techniques are used in geothermal areas but have rarely been employed to analyse plants growing in the area. At Waiotapu Geothermal Field, less than 10% of the surface is directly exposed, areas where the hyperspectral airborne successfully identified three main lithologies and alteration minerals; acid-sulphate alteration, “mixed” alteration, and silica-sinter deposition. While plants cover the remaining 90% of the surface, with kanuka shrub (kunzea ericoides var. microflora) as the dominant species in soils >40 °C. As such, kanuka was selected for our investigation and four geothermally relevant elements were chosen (Ag, As, Ba, and Sb). In areas with near-neutral high-chloride springs with a significant upflow (e.g. Champagne Pool), Ag, As, and Sb are enriched in rock/soil samples and are uptaken by kanuka plants. Whereas high Ba concentrations were found in plants living in peripheral areas where water mixing is taking place. The foliar element concentration zonation maps were successfully developed through classification using Random Forest and regression with Kernel Partial Least Squares. Employing ICPMS data and laboratory, airborne, and satellite hyperspectral (VNIR/SWIR) remote sensing data to create models to predict the foliar element concentrations. The results correspond well with the geology and thermal profile of Waiotapu Geothermal Field. Additionally, thermal anomalies selected from airborne TIR broadband imagery were studied using point pattern analysis such as randomness test-statistics, to map their preferred patterns and orientation, which appear to be controlled by subsurface permeability and water flow. This research opens new opportunities for geothermal exploration and monitoring through plants using hyperspectral imaging, which can overcome the limitations of geothermal exploration methods in densely vegetated areas.
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    Characterisation and numerical simulation of the Lower Manawatu Catchment hydrogeological system : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Earth Sciences at Massey University, Manawatu, New Zealand
    (Massey University, 2018) Zarour, Hisham Ibrahim Sabri
    The Lower Manawatu Catchment (LMC) hydrogeological system presents an example of extensive stratified heterogeneous aquifers. A conceptual model was developed for the system through systematic characterisation of its geology, soil, climate, hydrology, hydrogeology and hydrochemistry. Numerical groundwater flow modelling provided an effective integrated framework for the analysis. The developed knowledge and models are useful for the identification and comparison of land and water resources management options in the catchment. The research involved the development of a soil moisture balance modelling code to evaluate recharge. Stratigraphical modelling has been possible through incorporating imaginary lithological well logs and stratigraphical cross-sections in data-sparse areas. Geological material heterogeneity was represented in the groundwater flow model through hybridising zonal and pilot point calibration techniques. The developed soil moisture, geology and heterogeneity modelling techniques have universal applications. The study indicates that the LMC hydrogeological system is more suitably represented as a continuous groundwater flow system rather than a sequence of discrete aquifers and aquitards. Average groundwater recharge is estimated at about 25% of average rainfall. Average baseflow is estimated at about 10% of the average runoff, the equivalent to more than half the estimated average recharge. The LMC groundwater resource is mainly tapped at shallow depths, the locus where most of the interaction with surface water occurs. Catchment-scale steady-state numerical groundwater flow modelling suggests that in average groundwater abstraction may have been depleting overall surface water flow by about 5%. Groundwater levels in the LMC were found to be generally stable, implying sustainable resource development. Rising groundwater levels noted in the eastern and southern outskirts of Palmerston North may be related to prolonged practice of irrigation. No evidence of land use impacts on groundwater quality was found in the catchment. Nitrate concentrations are believed to have been kept at acceptable levels in groundwater due to denitrification stimulated by extensive organic content in some geological units. This thesis represents a one stop shop for information on groundwater in the LMC. The knowledge and tools developed through this research have immediate use in the LMC and elsewhere, and they provide solid basis for further work.