Why is the water of Lake Pukaki turquoise? The majority of water flowing into the headwaters of Lake Pukaki comes from large river systems that extend right back into the valleys of the Southern Alps. Feeding these rivers are large glaciers.

Glaciers are slow moving rivers of ice. As more and more snow falls, the weight of the new snow compresses the older layers until it becomes a thick, heavy layer of ice. Just like water, the ice collects in valleys and pushes its way down the valley, ripping loose rock from the valley walls and trapping it in the moving ice.

Such is the force, that the grinding action of rock against rock results in a powder as fine as flour.

The fine flour is carried with the ice down the valley until the warmth of the lower altitude reduces the ice to water.

In the case of Lake Pukaki, the glacial flour continues its journey in the river waters until it flows into the lake where the majority remains suspended within the water. This results in the turquoise colour.

Lake Pukaki is on the road to Aoraki Mt Cook, along the Ben Ohau Range in "Mackenzie Country", South Island, New Zealand.