PUKAKI, LAKE

Lake Pukaki is in Canterbury, 94 miles by road from Timaru. It has an area of about 31 square miles, and lies at about 1,620 ft above sea level. The country that comprises the 523 square miles of its catchment is drained by two main rivers, the Tasman and the Hooker. The Tasman River is fed by rainfall and melt water from the Tasman Glacier and its tributaries, the Murchison, Ball, Hochstetter, Rudolf, and numerous other glaciers. The Hooker River obtains its water from rain and melt water from the Hooker and Mueller Glaciers and their tributaries. The total inflow to the lake varies between 600 and 30,700 cusecs, with an average of about 5,000 cusecs, The lake water is not clear, as it carries much fine sediment in suspension, and is cold (46°F). The lake occupies the lower end of a glaciated valley and is confined by a moraine 16,000–18,000 years old.

The outflow, and consequently the storage capacity of the lake, is controlled by a dam (the lake level can be varied between 1,610 and 1,637 ft above sea level), thus enabling more effective use to be made of the water by the 105-megawatt Lake Waitaki hydro-electric station. Other stations planned or under construction will also use water from Pukaki.

The meaning of the name is obscure but, according to a legend, Raikaihaitu (who dug out the Southern Lakes), noticing the bulging appearance of the outlet, gave this name, meaning “bunched-up waters”.

by Leslie Eric Oborn, A.O.S.M., New Zealand Geological Survey, Christchurch.