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

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.