Waiwera: evolving understanding for management of a New Zealand shallow and low enthalpy geothermal system

Abstract. Waiwera in New Zealand is a small coastal village with a 50 °C warm reservoir of 400 m thickness directly underneath. Hydrogeological models support water management by providing insights into sustainable extraction from the system. It is artesian and the geothermal water is of meteoric origin percolating down to sufficient depth getting heated. It rises through a fault zone into the shallow and leaky aquifer. Therein the geothermal water mixes with cold fresh groundwater and sea water. The aim of the presented study is to summarise the scientific work over the past decades and the knowledge and progress in process understanding. New radiocarbon dating shows the geothermal water entering the reservoir to be >20 000 years old and underlines the topography driven recharge model. Water management plans helped curbing overproduction. Most recently the springs have restarted discharging geothermal water on the beach.