Allis, R.G. 1979 Thermal history of the Karapiti area, Wairakei. [s.l.]: [s.n.]. Report / Geophysics Division 137 38 p.
Abstract: A resurvey of the heat flow from the Karapiti Thermal Area indicates that its output is 220+/-40 MW. Prior to 1952 its heat output was 40+/-20 MW. This increased in the late 1950's and early 1960's, reaching a peak of 420 MW around 1964, before decreasing to its present value. The heat flow variations are related to the extraction of steam and water for geothermal power from the Wairakei production borefield 3 km away. With the drawdown in water level and the fall in pressure within the hydrothermal aquifer, approximately 3000 MW-years (9 x 1016 J) of stored heat was extracted from the aquifer and flowed from Karapiti causing the heat pulse. A five-fold increase in the heat and mass inflow between 1962 and 1964, induced by the drawdown, has stabilized the aquifer in the vicinity of the borefield, and the heat flow from Karapiti has stabilized accordingly
