Lake Pukaki is a natural lake but has been raised twice to provide water storage for power stations constructed or planned for the Upper and Middle Waitaki Hydro Schemes. The lake was first raised 9 metres in 1955 to give a depth of 71.5 metres and
a volume of about 5 x 109 m3. A second dam, the Pukaki High Dam, was completed in 1978 to raise the lake a further 37 metres and add 5.5 x 109 m3 to the volume. This will
create a lake with a maximum depth of 108 metres and a volume of more than 10 x 109 m3 . In accordance with the recommendation of the 'UNESCO Working Group on Seismic Phenomena Associated with Large Reservoirs' (Adams, et al, 1973), the New Zealand Electricity Division of the Ministry of Energy installed a seismic network around Lake Pukaki comprising 8 vertical and 1 three-component seismometers. This has been operating continuously since June 1975.