Lake Pukaki is an alpine lake running north-south along the northern edge of the Mackenzie Basin on New Zealand's South Island. Although it is a natural moraine-dammed lake, today the outflow, and consequently the storage capacity of the lake, is controlled by a man-made dam. This is an essential part of the hydro-electric power scheme that extends down the Waitaki Valley.br/br/The glacial feed to the lakes gives them a distinctive blue colour, created by glacial flour, the extremely finely ground rock particles from the glaciers.