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• Towed TEM has been used to map near-surface resistivity in geothermal areas. • Near-surface geothermal flow paths are identified. • Shallow boiling zones are identified. • These findings can be used for resource management and hazard planning. There is an increasing need to image the shallow (top 100 m) subsurface using geophysical techniques to inform resource use, resource protection, regulatory and policy development, community resilience, and, in general, how humans can live and interact with their environment. Geothermal systems are one such natural resource whose shallow hydrological structures are generally poorly understood, yet extensively utilised. Understanding the geothermal hydrology will inform potential environmental effects and the hydrothermal risk. The towed transient electromagnetic (tTEM) geophysical technique has been successfully applied to map permeability structures associated with current and/or historical near-surface geothermal flow and/or hydrothermal alteration in parts of the Rotorua and Wairakei-Tauhara Geothermal Fields, New Zealand. High-density tTEM measurements have enabled distinctive near-surface (top 100 m) resistivity anomalies to be identified and be interpreted. Large-scale resistivity anomalies that have been interpreted in this study include geothermal alteration associated with ascending boiling geothermal fluids, lateral near-surface permeable zones, and potential locations of aquifers that feed geothermal springs. Additional information is generally needed to differentiate between these potential causes of low resistivity anomalies. Contrasts in the modelled resistivities are stronger over "up-flow" areas (areas where near-boiling chloride-type water is rising close to the ground surface) compared to steam-heated geothermal areas. This is likely caused by vigorous processes (such as might be expected at the fluid-boiling interface) acting on the capping rock in the up-flow areas making the tTEM technique valuable in identifying potential fluid pathways from depth to the surface in these areas. New insights into the shallow permeability structure with possible near-surface boiling zones are located at 50 m below the ground at one of the study sites. Identification of these areas not only help understand how geothermal fluid moves from depth to the surface but can also contribute to managing the hydrothermal explosion hazard in these areas. [ABSTRACT FROM AUTHOR]

Hydrothermal ecosystems are of high conservation and scientific value, but they are sensitive to external perturbations that result from development. This study examines the composition of vegetation at four plots at the Wairakei-Tauhara geothermal field, New Zealand, using the Scott height-frequency method, ground temperatures at 0.1- and 1-m depth, soil pH, and photographic surveys. It highlights the response of plant communities, in particular that of Kunzea ericoides var. microflora, in terms of composition, structure, and biomass index values, measures changes in ground temperature, as well as provides baseline data against which to compare future changes. It was found that optimal growing conditions for K. ericoides var. microflora are at temperatures above background conditions with a slightly acidic pH. Plots with cooler, less acidic conditions support more diverse plant communities, which also promote the establishment of invasive species. This suggests that the largest threats to thermotolerant vegetation in New Zealand, including K. ericoides var. microflora, are further decreases in ground temperature because the establishment of invasive species may result in thermolerant vegetation being out-competed in hydrothermal ecosystems. Recognising and understanding the ecological diversity and dynamics of hydrothermal ecosystems, as well as acknowledging the competing interests between development and conservation, is key to the management and protection of these areas. [ABSTRACT FROM AUTHOR]