Co2 Discharge from Lake Rotoiti, New Zealand

Abstract

Twenty percent of the surface area of Okataina Caldera is covered with lakes. Lake Rotoiti located at the northwest edge of Okataina Caldera, hosts numerous underwater hydrothermal vents. Western Lake Rotoiti has relatively shallow waters (10-40m) and is closely associated with Tikitere and Taheke geothermal fields. Plumes of gas and bubbling warm water can be observed in the lake resulting in a 10-20 MW geothermal heat flux of Central Basin located at the centre part of Lake Rotoiti. In this study, we present the results of a lake survey that focuses on surface CO2 emission using the floating accumulation chamber method and sequential Gaussian simulation for processing the data. In addition, dissolved gas composition and surface CO2 flux measurement give us a better understanding of the degassing pathways and mechanism of the geothermal fluids in Lake Rotoiti. The result of this lake survey benefits from the comparison of natural greenhouse gas output of Rotoiti to other volcanic lakes in Okataina Caldera and in New Zealand.