A Geothermal Resource under Stress -- A Case Study from Rotorua, New Zealand

Abstract

Natural activity associated with the Rotorua Geothermal Field in New Zealand is failing because of stress imposed upon the resource by exploitation. The field has been exploited for direct use of the geothermal fluid for many years but drilling activities have expanded rapidly since the late 1950s. Today, about 450 wells draw up to 31,000 tonnes/day of fluid from geothermal aquifers. Since 1979 several significant alkaline chloride springs have collapsed and over the past 15-20 years there have been dramatic declines in the overall level of natural activity. Surveys of the hot spring area, Whakrewarew, have shown a 30% decline in natural heat flux since 1967-69. A 3 year program to monitor the hydrology of the Rotorua system has led to the development of a new conceptual model of the field. This in turn provide the foundation for a numerical model which can be used for future management of the field.