| Abstract |
Natural geothermal features, especially geysers, are sensitive to man made changes to their environment. Changes in level of the Waikato River at the Spa Sights, Taupo, due to operation of control gates on the river and lowering of the river bed, resulted in cessation of activity in the Waipikirangi and CrowÆs Nest geysers. Geysering was temporarily restored by ôsoapingö and changing the near surface plumbing of the geysers. Damming of the Waikato River and consequent formation of Lake Ohakuri led to flooding of parts of the Orakeikorako thermal area. Thermal features at low elevation were first stimulated and then drowned, whilst those at high level increased in activity. At Rotorua, removal of geothermal fluid by shallow domestic and commercial bores caused a decline in shallow pressures and in thermal activity at the Whakarewarewa Thermal Area. Since closure of bores within 1.5 km of the main geyser in 1986, pressures and some spring activity have increased. Major development of the geothermal resource at Wairakei since the early 1950Æs progressively aflected thermal features at Geyser Valley, Karapiti and$nally the Spa Sights. In the main hot spring areas, the frow rates, chloride concentrations and spring temperatures decreased, and the periodicity of geysers increased. In the Karapiti fumarolic and solfataric area, steam jlows increased initially then declined. The increase in steam flow was accompanied by more ji-equent hydrothermal eruptions. History of the interaction of man and nature in New Zealand shows that some of the effects of development can be reversed faction is taken early, but large scale development is incompatible with the preservation of thermal features in their natural state. Specifically targeted reinjection may allow adverse environmental effects to be minimised. |