Why is the water of Lake Tekapo turquoise?
The majority of water flowing into the headwaters of Lake Tekapo 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 Tekapo, the glacial flour continues its journey in the river waters of the Godley, Cass and Macaulay rivers until it flows into the lake where the majority remains suspended within the water. This results in the turquoise colour.
Lake Tekapo’s geographical and central location is protected from rough coastal weather by the Southern Alps in the west and the Two Thumb Range to the east. This allows this highland location to enjoy some of New Zealand’s highest sunshine hours and lowest average wind speeds. Rainfall is just 575 millimeters (23 inches) annually. Lake Tekapo is the largest of three parallel lakes in the South Island of New Zealand (Lake Pukaki and Lake Ohau). Covering an area of 83 square kilometres (32 sq mi), and at an altitude of 700 metres (2,300 ft) it is fed from the northern end Godley River.
The lake is a popular tourist destination, and several resort hotels are located at the township of Lake Tekapo. An astronomical observatory is located at Mount John, which is to the north of the town, and south of the small Lake Alexandrina.
Hydroelectricity: The lake’s original outflow was at its southern end, into the Tekapo River but in 1951, a power station now known was completed. Water from the lake was diverted through a 1.4-kilometre (4,600 ft) tunnel under the town to the power station, with the water originally being returned to the river. With the development Upper Waitaki hydroelectric scheme in the 1970s, water is now fed into a 26-kilometre (16 mi) canal which leads to the shores of Lake Pukaki. Following a turbine failure in 1986, a new Kaplan turbine was installed, with a more efficient design and higher output (42 000 HP). Today, the power station produces an average of 160 GWh annually, from a 25.2 MW capacity generator.
Church of the Good Shepherd is situated on the shores of Lake Tekapo.