Overview of the Rotokawa-Mokoia geothermal system, Bay of Plenty, Aotearoa New Zealand - geoscience, monitoring and use

Abstract

The Rotokawa-Mokoia Geothermal System (RMGS) is located on the eastern side of Lake Rotorua. The system is classified as Group 3 (conditional development) under the Bay of Plenty Regional Natural Resources Plan (RNRP) and the Regional Policy Statement (RPS), where extraction of geothermal water, heat and energy is provided for where significant adverse effects on Significant Geothermal Features (SGF) are avoided, remedied or mitigated. This paper presents high-level information gathered from over 50 years of geoscientific research and reporting, monitoring and the collation of use data by the Bay of Plenty Regional Council (BOPRC). The paper aims to summarise and present this available information in an accessible way for community engagement purposes for the current BOPRC Plan Change 11 (RNRP review) program. The RMGS extends from Mokoia Island to the northwest through to Rotokawa in the southeast, including the Rotorua Airport area and the bed of Lake Rotorua between Mokoia Island and the Airport. The main thermal areas are around the southeast shoreline of the Island and around Rotokawa. The geothermal surface features in both areas are fed by the same source aquifer at depth. The RMGS is relatively small compared to other high-temperature systems of the Taup? Volcanic Zone (TVZ). Subsurface temperatures are up to 115 °C at less than 100 m depth within the RMGS. While this is a relatively cool thermal resource compared to other high-temperature systems of the TVZ, the produced temperature suits the energy requirements for end uses (for example space and water heating). Current levels of use of geothermal water and energy is very low, however, being a small system, it is difficult to determine what this low level of use means to the health of the geothermal system and its surface features. An assessment of the size and hydrogeology of this geothermal resource would help to understand opportunities for sustainable use, while protecting the
significant geothermal surface features in the area as directed by the current and future planning frameworks.