Physical, microbiological and invertebrate characterisation of the Waikite Wetland post 2009 restoration works

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Reeves, R.R.; Power, J.F.; Boothroyd, I.K.G. 2011 Physical, microbiological and invertebrate characterisation of the Waikite Wetland post 2009 restoration works. Lower Hutt, N.Z.: GNS Science. GNS Science report 2011/23 71 p. + 1 CD

Abstract: Surface expressions of geothermal systems, such as hot springs and fumaroles, provide unique environments for geothermal ecosystems to develop. Developing the land around these geothermal areas can affect these ecosystems, such as reducing geothermal fluid flows, reduced heat flow and physical damage due to stock grazing. Rehabilitation of sensitive geothermal ecosystems that have been impacted by development is an emerging research area. Some forms of development (e.g., land that had been cleared for farming) may be amenable to remediation measures that attempt to restore at least some of the pre-development ecosystem over short to medium time frames. The Waikite Geothermal Field is a protected geothermal environment. The wetland area that makes up part of this field has undergone land clearing, grazing and alteration of waterways starting in the 1930’s. The Department of Conservation (DoC) embarked on restoring the Waikite wetland area in 2009. This included a land exchange with farmers, fencing, restoring water courses, plantings and weeding. The aims of this study were to characterise the current state of the Waikite geothermal wetland, using hydrogeological, geochemical and biological techniques. This included identifying and improving the understanding of geothermal inputs into the wetland and detecting physical, chemical and biological changes that may have resulted from changing management strategies of the wetland. The study identified several surface geothermal inputs into the wetland, including the Otamakokore Stream and geothermal springs in the north east corner of the wetland. Elevated ground temperature data along the Paeroa Fault Scarp, which forms the southern boundary of the wetland, suggest possible sub-surface flows along this zone. Mass balance and stream flow data show that the wetland gains approximately 14 l s-1 of geothermal fluids via subsurface flows. Water chemistry, water level, microbiological and invertebrate data does not show significant changes that can be attributed to the altered land management practices. However, small variations in microbial and invertebrate communities recorded at some sites are consistent with a change in the geothermal environment. Long term monitoring data is required at the Waikite wetland to determine the success of the DoC restoration project. (auth)