An Assessment of Heat Flow at Whakarewarewa

Abstract

The Thermal Reserve at Whakarewarewa on the southern boundary of Rotorua Geothermal Field is believed to have been under stress for a number of years. Artificia1 exploitation of the hydrothermal resource appears to be a significant contributor to the observed decline in natural activity. Although the decline has been described in detail it has been difficult to quantify the changes. Recently all the natural features at Whakarewarewa were resurveyed, the only preceding survey having been made in 1967-69. A total heat flux at Whakarewarewa of 158 MW is estimated on the basis of heat loss from springs due to evaporation, radiation and discharge, and allowing for ground surface heat flow and losses into the Puarenga Stream. The 1984 resurvey of 285 springs shows a reduction in heat flux of 31% over the 15 year period, while the heat flux through the ground surface has decreased by 23%.