Geothermal heat flow through the soil at Wairakei

Abstract

The variation of ground temperature with depth was measured between 1954 and 1961 at numerous locations in the Wairakei thermal area of New Zealand. Analysis of these data clearly shows that conduction is the dominant mechanism of heat transfer until the difference between the temperatures at the surface and at a depth of 1 metre reaches a value of about 25 deg C. For higher ground temperatures, heat transport by convection of a mixture of air and water vapour becomes progressively more important and the conductive effect becomes insignificant. These conclusions are used to present a simplified picture of the nature of the mechanisms in the transfer of heat to the surface in areas of steaming ground at Wairakei. The temperature data are also used to study the geothermal microclimate, to determine the thermal conductivity of the soil, and to derive relations between the temperatures at various depths used in practice for estimating the escape of natural heat from the Wairakei thermal area.