"Lake Pukaki is the second-largest of three roughly parallel alpine lakes running north-south along the northern edge of the Mackenzie Basin on New Zealand's South Island. The others are Lakes Tekapo and Ohau. All three lakes were created when the terminal moraines of receding glaciers blocked their respective valleys, forming moraine-dammed lakes.
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. Lake Pukaki covers an area of 169 km², and the surface elevation of the lake normally ranges from 518.2 to 532 metres above sea level." Source : Wikipedia