| Title | Monitoring changes in geothermal springs chemistry at Kuirau Park and Ohinemutu, Rotorua geothermal system - using field physical measurements as a cost-effective proxy for chemistry changes |
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| Authors | J. Raine, M. Zuquim, S. Zarrouk |
| Year | 2025 |
| Conference | New Zealand Geothermal Workshop |
| Keywords | Rotorua Geothermal System, environmental monitoring, Geochemistry, Kuirau, Ohinemutu |
| Abstract | Kuirau Park and Ohinemutu, located in the northwest of the Rotorua Geothermal System (RGS), experienced increased geothermal activity between 1998 and 2002 following the 1986 bore closure programme aimed at restoring the RGS's health. Despite their proximity, the geothermal features of these areas differ in geochemistry and field attributes such as temperature. A review of geochemical and field measurements, including recent data, shows agreement with previous surveys but highlights changes in two features. Feature RRF3014 (JC Fountain) shows signs of recovery, similar to features at Ohinemutu, while Feature RRF0715 (Mayor’s Mouth) has declined in pH, temperature, and electrical conductivity (EC) since 2017, indicating potential deterioration. Historical analysis reveals that increased geothermal activity between 1998 and 2002 correlated with rising pH, temperature, and EC in several features. These relationships were used to generate correlations with total dissolved solids (TDS), though dataset constraints limited further analysis. Changes in TDS can indicate adverse effects like groundwater dilution due to pressure decrease within the supporting geothermal aquifer. Electrical conductivity, pH, and temperature are easily measured in the field, while TDS and geochemistry require significant investment. Developing correlations between these parameters could be a powerful tool for screening the geothermal system and guiding further investigation with targeted chemical sampling. Focused work concentrating on changes and correlations between pH, EC and bicarbonate could be a cost-effective tool to monitor CO2 reinjection returns to geothermal surface features and monitoring wells. Future work should focus on improving models and correlations between field parameters and chemistry through more concurrent field measurements and geochemical sampling. Historical data has helped identify changes in pH and conductivity related to increased geothermal activity, which could warn of future activity spikes that pose health and safety risks and potential damage to property and infrastructure. |