Collection and initial assessment of terrestrial heat flux of the Waiotapu Geothermal Field

Seward AM, Brakenrig T, Macdonald N, Shanks, J. 2022. Collection and initial assessment of terrestrial heat flux of the Waiotapu Geothermal Field. Lower Hutt (NZ): GNS Science. 79 p. (GNS Science report; 2022/07). doi:10.21420/ECCP-E459.

Abstract
Between 15 and 22 January 2020, stream flow gauging, water sampling, surface calorimeter and temperature-depth profile measurements were undertaken at Waiotapu Geothermal Field (WGF) as part of a surface heat loss assessment. The data summarised in this report will be used to revise an estimate of heat loss from the WGF. This survey was designed in parallel with an aerial thermal infrared (TIR) survey undertaken over the region on 13 April 2019. Water temperatures, flowrates and water samples were collected at 19 sites. Chemical analysis of the water samples was undertaken at NZGAL for total bicarbonate, pH and chloride and sulphate concentrations. Eight calorimeter measurements and 10 temperature-depth profiles were collected are locations representing differing types of groundcover and assumed heat fluxes. A total heat loss from the WGF was calculated from the chloride flux and stream temperature data. Based on chloride flux in flowing streams a heat loss of 188 MW is determined, while estimation using measured water temperatures determine a heat loss of 142 MW from the system. Heat loss through the ground will be calculated from calorimeter and temperature-depth profiles in combination with the development of the groundcover map. (The authors)