The effects of seasonal variations in rainfall and production on the aquifer and surface features of Rotorua geothermal field

• Published in: Geothermics 2017-09, Vol.69, p.165-188
• Main Authors: Ratouis, Thomas M.P., O’Sullivan, Michael J., Alcaraz, Samantha A., O’Sullivan, John P.
• Format: Article
• Language: English
• Subjects: Aquifers; Calibration; Effects; Exploitation; Feature recognition; Geothermal modelling; Geothermal power; Geysers; Hot springs; Mathematical analysis; Mathematical models; Monitoring programme; Rain; Rainfall; Reservoirs; Resource management; Rotorua geothermal field; Seasonal variations; Seasons; Water level fluctuations; Water levels; Water springs
• ISSN: 0375-6505; 1879-3576
• DOI: 10.1016/j.geothermics.2017.05.003

•Paper describes new numerical simulations of the Rotorua geothermal field.•Focuses on the effects of both natural and anthropogenic seasonal disturbances on the reservoir and the surface features.•Test the capability of the numerical model to reproduce the behaviour of individual surface features in order to better evaluate the effects of reservoir management (wellbore closure programme) on the reactivation of old surface manifestations. The Rotorua geothermal field is a shallow geothermal reservoir lying directly beneath Rotorua City in New Zealand. It is renowned for an abundance of natural geothermal manifestations including the geysers and hot springs at Whakarewarewa. Over-exploitation of the geothermal resource in the 1970s leading to the decline of many active surface features was recognised and subsequently addressed by a change of management policy. A wellbore closure programme was instigated in 1986 by the New Zealand government which resulted in the recovery of some of the geothermal features. The monitoring programme continues through to the present day and provides valuable data which is used for the calibration of the new numerical model of the Rotorua system presented here. This model focuses on seasonal factors that control water level fluctuations in the geothermal reservoir as well as the behaviour of individual surface features. The matches of model temperatures with field data from individual surface features are very promising and the model may assist with sustainable management of the geothermal resource.